Note: Descriptions are shown in the official language in which they were submitted.
1334592 D.N. 4723B
- l - 22749-341
PYRIDINYL-QUINOLONE COMPOUNDS, THEIR PREPARATION AND USE
BACKGROUND OF THE INVENTION
a) Field of the Invention
This invention relates to novel 4-oxo-3-quino-
linecarboxylic acids, to methods for the preparation
thereof, and compositions and methods for the use thereof
as antibacterial a~ents.
b) Information Disclosure Statement
Antibacterially active 4-oxo-3-quinolinecarbox-
ylic acids are known in the prior art which includes the
following references.
Lesher and Carabateas U.S. Patent 3,753,993,
issued August 21, 1973, discloses 7-(2,6-dimethyl-4-pyri-
dinyl)-l-ethyl-1,4-dihydro-4-oxo-3-quinolinecarboxylic
acid.
Sterling Dru~ Inc. European Patent Application,
published April 30, 1986 under No. 179,239, discloses
7-(2,6-dimethyl-4-pyridinyl)-1-ethyl-6-fluoro-1,4-dihydro-
4-oxo-3-quinolinecarboxylic acid.
Grohe et al. U.S. Patent 4,670,444, issued June
2, 1987 (Bayer AG European Patent 78,362, published May
11, 1983) discloses 1-cyclopropyl-6-fluoro-7-(l-piper-
azinyl)-1,4-dihydro-4-oxo-3-~uin~inecarbxylic acid, also
known under the ~eneric name ciprofloxacin.
D.N. 4723A
-2- 1334592
Gilligan et al. U.S. Patent 4,636,506, issued
January 13, 1987, discloses compounds of the formula
F ~ C2Rl
11 ll
R2 ~ ~N/
R3 y
wherein
Rl is hydrogen, a pharmaceutically acceptable-
cation or alkyl of 1 to 3 carbon atoms;
Y is selected from the ~roup consisting of alkyl
and haloalkyl of 1 to 3 carbon atoms, allyl, vinyl, cyclo-
propyl, hydroxyethyl, phenyl, 4-hydroxyphenyl and
4-fluorophenyl;
R2 i8 3-pyridyl or 4-pyridyl which may be sub-
stituted by one or two substituents selected from the
group consisting of fluoro, chloro, hydroxy, alkoxy of
1 to 4 carbon atoms, amino, dialkylamino of 2 to 8 carbon
atoms, hydroxyalkyl of 1 to 6 carbon atoms, aminoalkyl
of 1 to 6 carbon atoms; 5-pyrimidyl, or 6-quinolyl, and
R3 is fluoro;
and the acid addition salts thereof when Rl is hydroRen.
Example 1 of the patent discloses the preparation of 6,8-
difluoro-1-ethyl-7-(4-pyridinyl)-4-oxo-3-quinolinecarbox-
ylic acid.
-- 3
133~92 22749-341
SUMMARY OF THE INVENTION
In a product aspect, the invention relates to
compounds of the formula:
R' O
COOR
CH3 Rn
I
(wherein:
R is hydrogen or lower-alkyl;
R' is selected from the group consisting of hydrogen,
fluoro and -SR"';
R" is selected from the group consisting of hydrogen,
fluoro and -SR"', where R"' is phenyl, benzyl or lower-alkyl with
the proviso that when R" is hydrogen, R ' is also hydrogen)
and to acid-addition salts thereof; and alkali metal or amine
salts of compounds where R is hydrogen.
Preferred are the compounds of formula I wherein R'
and R" are other than -SR"'.
When R' and/or R" is -SR"', preferred are those of
formula I wherein (1) R" is -SR"' and R" is fluoro or (2) both
R ' and R" are -SR"'.
Some of the compounds of formula I are useful as
intermediates for producing other compounds of formula I, in
addition to being useful as antibacterial agents.
Especially preferred are the compounds of formula I
wherein R is hydrogen and R' and R" are hydrogen or fluoro,
with the proviso that when R" is hydrogen, R' iS also hydrogen,
13 3 4 S 9 2 22749-341
which compounds have outstanding antibacterial activity.
The compounds of formula I: have antibacterial
activities. Hence, in a further product aspect, the invention
relates to compositions for combating bacteria which comprise
an antibacterially effective amount of a compound of formula I
in admixture with a suitable carrier or diluent.
D.N. 4723A
_4_ 1 3 34 ~9 2
In a process aspect, the invention relates to
a process for preparing a compound of Formula I where R
i8 hydrogen and R' i8 hydrogen or fluoro which comprises:
(a) reactinR a compound of the formula:
R~
11
N~
R"
wherein R is lower-alkyl, R' is hydrogen or fluoro, R"
is hydrogen or fluoro and X is chlorine, bromine or
iodine, with a compound of the formula:
Sn-(Alk)3
CH3 ~ ~L CH3
wherein Alk is alkyl of 1-6 carbon atoms, in the presence
of a palladium complex catalyst; and
(b) hydrolyzing the resulting ester where X is
replaced by 2,6-dimethyl-4-pyridinyl.
In a further process aspect, the invention
relates to a process for preparing a compound of Formula
I where R and R' are hydrogen which comprises:
(a) reacting a compound of Formula I where R
is alkyl of 1-6 carbon atoms and R' '~i-s fluoro, with a
sulfide, R"'SH, in the presence of sodium hydride to pro-
duce 8 compound according to Formula I where R' is -SR"';
and
13~4S92
(b) heating the latter compound with Raney nickel
to replace the -SR"'group by hydrogen.
In a still further process aspect, the invention
relates to a method of combating bacteria which comprises
contacting the locus of said bacteria, including administration
to a mammalian host, with a composition containing an anti-
bacterially effective amount of a compound of formula I where
R is hydrogen and R' is hydrogen or fluoro.
DETAILED DESCRIPTION INCLUSIVE OF PREFERRED EMBODIMENTS
In the definitions of R and R"'in formula I above,
the term "lower-alkyl" stands for alkyl preferably having one
to six carbon atoms which may be straight or branched.
The invention also contemplates acid-addition salts
including pharmaceutically acceptable acid-addition salts of
the compounds of formula I. The nature of the pharmaceutically
acceptable acid-addition salt is immaterial provided it is
derived from an acid the anion of which is essentially
innocuous to animal organisms. Examples of appropriate acid-
addition salts include the hydrochloride, hydrobromide, sulfate,
methanesulfonate, maleate, citrate, tartrate, p-toluenesulfonate,
cyclohexanesulfamate, and the like. When the compounds are used
as intermediates, they may be acid-addition salts which are not
pharmaceutically acceptable.
-- 6
- 13 3~ 5 9 2 22749-341
The compounds of formula I where R' is hydrogen can
also be prepared and used in the form of their alkali metal or
amine salts, preferably pharmaceutically acceptable metal or
amine salts, such as the sodium, potassium, ethylenediamine or
N-methylglucamine salts.
The following flow sheets show preferred routes to
prepare the compounds of formula I starting from readily
available materials.
D.N, 4723A
_7_ 1334592
FLOW SHEET A
X ~ X CHA31CC0131 X ~ COCH3
III IV
¦AlkOC-OAlk
~ NaH
F ~ COOH 1. SOC12 F ~ CCH2COOAlk
X ~ ~ X' COOAlk X ~ / LX'
(BuLi)
VI V
¦ DMF dimethyl
I acetal
O O
F ~ C C-COOAlk ~ NH2 ~ C C-COOAlk
X ~ ~ X' HC-N ~ < X ~ X' HC-N(CH3)2
VIII VII
l K2C3
F ~ _ COOAlk ~ -(Alk)3 ~ COOAlk
N~ CH3 ~ ~ CH3 N
~ Pd-catalyst CH3 ~
II (R' and R" = H) I (R' and R" = H)
H20 (base or
~ acid)
I (R, R' and R" = H)
D.N. 4723A
133~592
--8--
The above Flow Sheet A illustrates the prepa-
ration of l-cyclopropyl-7-(2,6-dimethyl-4-pyridinyl)-6-
fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid (I;
R, R' and R" = H). A 2,4-dihalofluorobenzene (III; X =
Cl, Br or I, X' = F, Cl, Br or I) is subjected to a
Friedel-Crafts reaction with acetyl chloride in the
presence of aluminum chloride to give the correspondin~
halo substituted acetophenone (IV). The latter is caused
to react with a dialkyl carbonate (Alk = alkyl of 1-6-
carbon atoms) in the presence of sodium hydride to ~ivean alkyl benzoylacetate of Formula V. The compound of
Formula V can alternatively be prepared from a 3-fluoro-
4,6-dihalobenzoic acid (VI) by first convertin~ the latter
to its acid chloride with thionyl chloride and treating
the acid chloride with a half ester of malonic acid in
the presence of butyllithium. The benzoylacetate (V) is
then treated with dimethylformamide (DMF) dimethyl acetal
[(CH3)2NCH(OCH3)2] to form a 3-dimethylaminopropenoate
(VII). The latter i8 then treated with cyclopropylamine
to produce the correspondinR 3-cyclopropylaminopropenoste
(VIII). Cyclization of VIII is carried out by heating
in the presence of a base, preferably potassium carbonate,
to give a com~ound of Formula II (R' and R" = H). The
l-cyclopropyl-6-fluoro-8-halo-1,4-dihydro-4-oxo-3-quino-
linecarboxylate (II) is then caused to react with a2,6-dimethyl-4-(trialkylstannyl)pyridine in the presence
of a palladium complex catalyst, thereby producin~ an
D.N. 4723A
1~3~592
ester of Formula I where R' and R" = H. The latter can
then be converted to the free acid (I; R, R' and R" = H)
by a conventional hydrolysis reaction with base or acid.
In the conversion of II to I, the process is
carried out using approximately equimolar amounts of II
and the organotin compound in an inert solvent at a
temperature between about 50C and 100C, conveniently
at the reflux temperature of the solvent. The reaction
is complete in a period ranging from 1-24 hours. Alterna--
tively, the reactants and catalyst can be heated in apresssurized vessel in an inert atmosphere (e.g. argon,
nitrogen) at a temperature between about 125 and 175C
until the reaction is complete (1-5 hours). The palladium
complex catalyst, present to the extent of about 5 mole
percent, can be any such catalyst known to effect
cross-coupling of organotin compounds with organic halides
[cf. Kosugi et al., Bull. Chem. Soc. Japan 59, 677-679
(1986)], for example, PdC12(PPh3)2, Pd(PPh3)4, PdC12~P(o-
tolyl)3]2, PdC12+2P(OEt)3 and PdC12(PhCN)2. A preferred
catalyst is dlchlorobis(triphenylphosphine)palladium
[PdC12(PPh3)2]-
D.N. 4723A
133~92
-1()-
FLOW SHEET B
Br~ P Li F ~_ COOH PC15 F ~COCl
IX X
XI .
CH2COOH
COOAlk
BuLi
F O
F ~ C - C-COOAlk DMF dimethyl F ~ CCH2COOAlk
Br ~\~ F HC-N(CH3)2 < Br ~ F
XIII XII
NH2
F O
F ~ ~ C --C-COOAlk F ~ ~
Br ~ F HC-N ~ K2CO3> Br ~ ~ COOAlk
F F ~
XIV II (R' and R" = F)
CH3
N ~ Sn-(Alk)3
~ \
CH3 1-
Pd catalyst V
rcontd. ]
D.N. 4723A
- 1334592
FLOW SHEET B [contd.]
F O F O
N ~ ~r < N~lr COOAlk
~r~~ ~ N~ (base or ~ N~
CH3 F ~ CH3 F ~
I (R=H, R' and R"=F) I (R' and R" = F)
The above Flow Sheet B illustrates the prepara-
tion of l-cyclopropyl-7-(2,6-dimethyl-4-pyridinyl)-5,6,8-
trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid
(I; R - H, R' and R" ~ F). 1,4-Dibromo-2,3,5,6-tetrafluo-
robenzene (IX) is metalated with butyllithium and then
caused to react with carbon dioxide to give
4-bromo-2,3,5,6-tetrafluorobenzoic acid (X). The latter
is converted to its acid chloride (XI) which reacts with
a half ester of malonic acid in the pre~ence of butyl-
lithium to afford an alkyl 4-bromo-2,3,5,6-tetrafluoro-
benzoylacetate (XII). A series of transformations (XII
- > XIII -> XIV -> II) entirely analo~ous to the
sequence V -> VII -> VIII -> II in Flow Sheet A
affords an alkyl 7-bromo-1-cyclopropyl-5,6,8-trifluoro-
1,4-dihydro-3-quinolinecarboxylate (II; R' and R" = F).
Reaction of the latter with 2,6-dimethyl-4-(trialkylstan-
I D.N. 4723A
1334592
-12-
nyl)pyridine in the presence of a palladium complex cata-
lyst Rives I (R = alkyl, R' and R" = F) which i8 readily
hydrolyzed to the free acid I (R = H, R' and R" = F) .
FLOW SHEET C
1 R"'-S O-
r~~ ~ N ~ NaHN ~ N ~ COOR
CH3 F ~ CH3 F ~
(R ' and R" = F) I (R ' - R "' S, R" = F)
Raney Ni
v
~J COOR
CH3 F ~
(R ' = H, R" = F)
The above flow sheet illustrates the preparation
of l-cyclopropyl-6,~-difluoro-1,4-dihydro-7-(2,6-dimeth-
yl-4-pyridinyl)-4-oxo-3-quinolinecarboxylic acid ( I; R
and R ' = H, R" = F) . The process involves the replacement
of the 5-fluoro substituent by hydrogen in the 5,6,8-tri-
D.N. 4723A
1334592
-13-
fluoro compound prepared according to Flow Sheet B. The
reactions can be carried out either on the ester (R =
alkyl) or free acid (R = H). The trifluoro compound (I;
R' and R" = F) is caused to react with a thiol (R"'SH, R"'
= alkyl, benzyl or phenyl) in the presence of sodium
hydride to give a corresponding compound where the
5-fluoro substituent is replaced by R"'-S. When the
latter compound is heated with Raney nickel in a solvent
such as ethanol, the thiol group is removed to give I (R'
= H, R" = F). In some cases there is some tendency for
the 8-fluoro group also to be replaced by thiol leading
to a mixture of products which, however, are readily sepa-
rated by fractional crystallization or chromatography.
An alternative approach to the preparation of
I (R' = H, R" = F'), which avoids the removal of the
eventual 5-fluoro substituent according to Flow Sheet C,
is accomplished starting with the commercially available
2,3,4,5-tetrafluorobenzoic acid following the sequence
of reactions outlined in Flow Sheet D below.
D.N. 4723A
-14- 133~592
FLOW SHEET D
F ~ COOH F ~ COOAlk
NaN3
Pd/C F ~ COOAlk
XVII XVI
n-BuONO
CuBr2
O Sn(Alk)3
F_ ~ COOAlk ~ CH3 F ~ ~ COOAlk
F CH3 ~ N'~ 3 N ~ ~ ~N~
~ Pd-catalyst CH3 A
XVIII I (R' = H, R" = F)
¦ H20 (base or
v acid)
I (R and R' = H, R" = F)
D.N. 4723A
133~592
-15-
Compound XV is produced from 2,3,4,5-tetrafluo-
robenzoic acid by a series of steps corresponding to the
sequence VI -~ V -> VII -> VIII -> II on Flow Sheet
A. In order to replace the 7-fluoro group by bromine
prior to the tin-coupling reaction, compound XV is caused
to react with sodium azide to give the 7-azido compound
XVI. The latter is hydrogenated in the prese-nce of
palladium-on-carbon to form the 7-amino compound XVII
which is converted to the 7-bromo compound XVIII by-
reaction with n-butyl nitrite and cupric bromide. The
tin-coupling reaction with 2,6-dimethyl-4-(trialkylstan-
nyl)pyridine produces the ester of the desired compound
of Formula I where R' = H and R" = F.
A further alternative approach to the prepa-
ration of I (R' = H, R" = F') uses 2,4-dichloro-5-fluoro-
benzoic acid as starting material. The latter can be con-
verted according to the transformations of Flow Sheet A
to ethyl 7-chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-4-
oxo-3-quinolinecarboxylate, which can be coupled directly
with 2,6-dimethyl-4-(trialkylstannyl)pyridine.
The structures of the compounds were established
by the modes of synthesis, by elementary analyses and by
infrared, nuclear magnetic resonance and/or mass spectra.
The following examples will further illustrate
the invention.
D.N. 4723A
1334~g2
-16-
Example 1
a) 4-Bromo-2,5-difluoroacetophenone [IV; X = Br, X' = F].
To a stirred mixture of 20 g 2,5-difluorobromo-
benzene and 35.2 8 aluminum chloride under nitrogen at
60C was added dropwise 11.2 ml acetyl chloride. The
reaction mixture was stirred at 95C for 90 min. and then
poured over 250 g ice followed by 17 ml concentrated
hydrochloric acid. The aqueous mixture was extracted with
ether, and the extracts washed with sodium chloride solu--
] tion and concentrated. The residue (23.6 R) was distilledin vacuo to give 18.4 ~ (76%) 4-bromo-2,5-difluoroaceto-
phenone, b.p. 65C (0.1 mm).
b) Ethyl 4-bromo-2 t 5-difluorobenzoylacetate [V; Alk
C2Hs, X = Br, X' = F].
To a stirred mixture of 18 g 4-bromo-2,5-difluo-
roacetophenone and 233 ml diethyl carbonate cooled in an
ice-bath was slowly added 6.4 g sodium hydride (60% in
oil). The reaction mixture was heated at 80C for 90 min.
and then added to 700 ml ice containing 25 ml acetic acid.
The aqueous mixture was extracted with ether, and the
ether extracts were washed with sodium chloride solution,
dried (magnesium sulfate) and concentrated. The residue
was distilled, collecting the material (15.33 g) boiling
at 85-135C (0.05 mm.). The latter material was chromato-
graphed on 185 g silica gel (Kieselgel 60) usinR 20% etherin hexane as eluant to give 6.69 g ethyl 4-bro~o-2,5-di-
fluorobenzoylacetate as the first product to be eluted.
3~
D.N. 4723A
-17- 133~592
c) Ethyl 4-bromo-2,5-difluorobenzoylacetate ~V; Alk
C2Hs, X = Br, X' = F]-
A solution of 37 g monoethyl malonate and 18
mg 2,2'-biquinoline in 775 ml dry tetrahydrofuran was
cooled to -30C under nitrogen. To this solution was
added dropwise 215.6 ml 2.6M n-butyllithium in hexane.
The reaction mixture was allowed to warm to -5C, then
cooled to -30C and another 20 ml butyllithium was added.
Repetition of the procedure with another 5 ml butyllithium-
completed the metalation of the monoethyl malonate. Theresulting reagent mixture was` cooled to -50C and
4-bromo-2,5-difluorobenozyl chloride (prepared from 22.28
g 4-bromo-2,5-difluorobenzoic acid and thionyl chloride)
was added dropwise. The reaction mixture was then stirred
at room temperature for 1 hour, then cooled and 750 ml
lN hydrochloric acid was added. The aqueous mixture was
extracted with ether, and the extracts were washed with
saturated sodium bicarbonate and sodium chloride
solutions, dried (magnesium sulfate) and concentrated.
The residue crystallized from hexane to give 21.0 g ethyl
4-bromo-2,5-difluorobenzoylacetate, m.p. 51-53C.
d) Ethyl 2-(4-bromo-2,5-difluorobenzoyl)-3-dimethylamino-
propenoate [VII; Alk = C2Hs, X = Br, X' = F].
To a stirred solution of 2.17 g ethyl 4-bromo-
2,5-difluorobenzoylacetate in 5 ml tetrahydrofuran was
added 0.94 ml dimethylformamide dimethyl acetal. The
reaction mixture was stirred at room temperature for 24
D.N. 4723A
133~92
-18-
hours and then concentrated in vacuo to ~ive 2.63 R of
an oran,~e oil which was used directly in the next reac-
tion.
e) Ethyl 2-(4-bromo-2,5-difluorobenzoyl)-3-cyclopropyl-
5 aminopropenoate [VIII; Alk - C2Hs, X = Br, X' s Fl-
The product of part (d) above was dissolved in10 ml tetrahydrofuran and cooled in an ice-bath. -Cyclo-
propylamine (0.5 ml) was added and the reaction mixture
was stirred at ()C for 1 hour. The mixture was concentra--
10 ted in vacuo to ~ive 2.52 g of an orange oil which wasused directly in the next reaction.
f) Ethyl 7-bromo-1-cyclopropyl-6-fluoro-1,4-dihydro-4-
oxo-3-quinolinecarboxylate [II; R = C2Hs, R' and R" = H,
X = Br].
A mixture of the product of part (e) and 1.8
,~ potassium carbonate in 10 ml dimethylformamide was
heated at 100C (steam bath) for 1 hour. The reaction
mixture was added to water and the product was collected
by filtration, dried, and recrystallized from ethanol to
20 give 1.2 ~ ethyl 7-bromo-1-cyclopropyl-6-fluoro-1,4-di-
hydro-4-oxo-3-quinolinecarboxylate, m.p. 251-253C.
~) 2,6-Dimethyl-4-(trimethylstannyl)pyridine.
To a mixture of 100 g sodium (3()% dispersion
in toluene) and 400 ml dimethoxyethane (DME) cooled in
25 an ice-salt bath and under nitro~en was added a solution
of 121 g trimethyltin chloride in 50 ml DME over a 2 hour
D.N. 4723A
-19- 1~34592
period while keeping the temperature below 5C. The mix-
ture was stirred at 0-5C for 2.5 hours and then 70
4-chloro-2,6-dimethylpyridine in 50 ml DME was added over
a 1.5 hour period while keeping the temperature at 0-10C.
The reaction mixture was stirred at the latter temperature
for 1 hour and then allowed to stand at room temperature
overnight. The mixture was filtered and concentrated,
and the residue treated with ether and again filtered and
concentrated. The re~ulting orange liquid was distilled,-
collecting the material boilin~ at 130C (20 mm) to give80 g 2,6-dimethyl-4-(trimethylstannyl)pyridine.
The starting material, 4-chloro-2,6-dimethyl-
pyridine, was prepared by heating (8 hours at reflux) 2,6-
lutidine-N-oxide hydrochloride with phosphorus oxychlor-
ide. The crude product, a mixture of 4-chloro-2,6-dimeth-
ylpyridine and 2-chloromethyl-6-methylpyridine, was
purified by heating it with triethylamine in ethanol
whereby the byproduct was converted to its triethyl
quaternary ammonium salt (monohydrate, m.p. 103-104C)
which wa~ readily ~eparated from the de~ired 4-chloro-
2,6-dimethylpyridine by aqueous extraction. In this way
a 56.6% yield of 4-chloro-2,6-dimethylpyridine (b.p. 71-
73C, 15 mm.) from the N-oxide was obtained.
D.N. 4723
-20- 133 4~g2
h) Ethyl l-cyclopropyl-7-(2,6-dimethyl-4-pyridinyl)-6-
fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylate [ I; R
C2Hs, R' and R" = H]-
2,6-Dimethyl-4-(trimethylstannyl)pyridine (part
~) (10.1 R) and 1.52 ~ dichlorobis(triphenylpho~phine)-
palladium was added to a stirred solution of 12.13 ~ ethyl
7-bromo-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-3-quino-
linecarboxylate (part f) and 10 ml hexamethylphosphoramide
(HMPA) in 240 ml dioxane under nitro~en. The reaction
mixture was heated under reflux for 24 hours, then cooled
and partitioned between water and methylene dichloride.
The organic extract was washed with sodium chloride solu-
tion, dried (magnesium sulfate) and concentrated to Rive
12.0 R ethyl l-cyclopropyl-7-(2,6-dimethyl-4-pyridinyl)-
6-fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylate, m.p.
198-200C.
i) l-Cyclopropyl-7-(2,6-dimethyl-4-pyridinyl)-6-fluoro-
1,4-dihydro-4-oxo-3-quinolinecarboxylic acid [I; R, R'
and R" = H].
A suspension of 12.4 ~ ethyl 1-cyclopropyl-7-
(2,6-dimethyl-4-pyridinyl)-6-fluoro-1,4-dihydro-4-oxo-3-
quinolinecarboxylate in 320 ml water containinR 3.5 ~
sodium hydroxide was heated at reflux for 2.5 hours. The
D.N. 4723A
-21- 1334592
reaction mixture was then decolorized with charcoal,
filtered and brought to pH 5-5.5 with acetic acid. The
solid that precipitated was collected, dried in vacuo and
recrystallized from dimethylformamide to give 8.4 g
1-cyclopropyl-7-(2,6-dimethyl-4-pyridinyl)-6-fluoro-1,4-
dihydro-4-oxo-3-quinolinecarboxylic acid, m.p. 300-
302C(decompn.).
A 2.50 g sample of the product was heated with
10 ml ethylenediamine to 50-60C, then cooled to room
temperature and the solid product isolated and dried to
give 1.80 g of the ethylenediamine salt monohydrate,
yellowish powder, m.p. 303-305C.
Example 2
a) 2,4-Dichloro-5-fluoroacetophenone [IV; X and X' = Cl]
was prepared from 49.5 g 2,4-dichlorofluorobenzene and
33 g acetyl chloride in the presence of 102 g aluminum
chloride according to the procedure described in Example
1, part (a), and was obtained in 55% yield as a liquid,
b.p. 89-90C (2.5 mm.).
b) Ethyl 2,4-dichloro-5-fluorobenzoylacetate [V; Alk
C2Hs, X and X' = Cl] was prepared from 50 g 2,4-dichloro-
5-fluoroacetophenone and diethylcarbonate in the presence
of sodium hydride according to the procedure described
in Example 1, part (b), and was obtained in 47% yield as
a liquid, b.p. 125-135C (0.25 mm.).
D.N. 4723A
- 133~592
-22-
c) Ethyl 2-(2,4-dichloro-5-fluorobenzoyl)-3-dimethylamino-
propenoate [VII; Alk = C2Hs, X and X' = Cl] was prepared
from 10 R ethyl 2,4-dichloro-5-fluorobenzoylacetate and
5 ml dimethylformamide dimethylacetal accordin~ to the
procedure of Example 1, part (d), and the crude product
used directly in the next reaction.
d) Ethyl 2-(2,4-dichloro-5-fluorobenzoyl)-3-cyclopropyl-
aminopropenoate [VIII; Alk = C2Hs, X and X' = Cll was
prepared from the crude product of part (c) and 2.24 g~
cyclopropylamine accordinR to the procedure of Example
1, part (e), snd the crude product used directly in the
next reaction.
e) Ethyl 7-chloro-1-cyclopropyl-6-fluoro-1,4-dihydro-4-
oxo-3-quinolinecarboxylate lII; R = C2Hs, R' and R" = H,
X - Cl] was prepared from the crude product of part (c)
and 9.88 g potassium carbonate according to the procedure
of Example 1, part (f) to ~ive 7.0 R of solid product (63%
overall yield from the ethyl 2,4-dichloro-5-fluorobenzoyl-
acetate of part b).
f) 1-Cyclopropyl-7-(2,6-dimethyl-4-pyridinyl)-6-fluoro-
1,4-dihydro-4-oxoquinolinecarboxylic acid lI; R, R' and
R" = H]-
Ethyl 7-chloro-1-cyclopropyl-6-fluoro-1,4-dihy-
dro-4-oxo-3-quinolinecarboxylate (3.0 R) wa~ caused to
react with 3.0 R 2,6-dimethyl-4-(trimethylstannyl)pyridine
in the presence of 435 mR dichlorobis(triphenylphosphine)-
palladium in dioxane medium according to the procedure
D.N. 4723A
I33~5g2
-23-
of Example 1, part (h). The crude product in methanol
solution was chromatographed on 100 g silica gel and
eluted with 5-20% methanol in ether. The fractions con-
taining the desired ethyl ester were combined and hydro-
lyzed with 50 ml 3N hydrochloric acid on a steam bath for3.5 hours. The reaction mixture was cooled, extracted
with chloroform and the aqueous layer concentrated to dry-
ness. The residue was made basic with 10~/o aqueous potas-
sium carbonate, filtered and acidified with acetic acid.
The solid product was collected and dried to give 1.6 g
l-cyclopropyl-7-(2,6-dimethyl-4-pyridinyl)-6-fluoro-1,4-
dihydro-4-oxoquinolinecarboxylic acid, m.p. 302-303C,
identical with the final product of Example 1.
Example 3
a) 1,4-Dibromo-2,5-difluorobenzene.
A 5 L flask was charged with methylene chloride
(2.15 L). The vessel was placed under a nitrogen atmo-
sphere and aluminum bromide (100 g, 0.37 m) was added with
stirring to form a solution. l,4-Difluorobenzene (901
ml, 8.76 m) and bromine (898 ml, 17.43 m) were added in
portions over a period of 4.5 hours.
The reaction was stirred overnight and then
heated to 40C for thirty minutes to expel most of the
gaseous hydro~en bromide. The cooled solution was
quenched into water (12 L) with rapid stirring. The lower
layer was removed and concentrated at atmospheric pressure
on a steam bath. When most of the methylene chloride had
D.N. 4723A
- 1334~92
-24-
been removed, hexane (500 ml) was added and the distilla-
tion was continued until a head temperature of 65C was
reached. The residue was diluted with hexane (2 L) and
cooled to -5C usin~ a Dry Ice/isopropanol bath. The
resulting white solid was collected and washed with 500
ml of cold (-30C3 hexane. Two additional crops were
obtained by cooling the mother liquors to -20 and -40C
respectively. The low melting solids were dried for 16
hours at room temperature in vacuo. The first two crops-
totalinR 1424 g (59. 8~/o yield) were pure enough (>98%) tobe carried forward.
b) 4-Bromo-2,5-difluorobenzoic acid [VI; X = Br, X' = F].
To a cold (-60C) solution of 1,4-dibromo-2,5-
difluorobenzene (700 g, 2.56 moles) in anhydrous ether
(10 L) under nitrogen was added a cold (-60C) dilute
solution of n-butyllithium in hexane [1.70 L (2.7 moles)
of 1.6M n-butyllithium in hexane diluted with an addi-
tional 4. 8 L of hexane] over a two hour period. Dry Ice
(0.5 kg) was added to produce a white precipitate and the
temperature rapidly rose to -35C before falling back to
-50C. The slurry was allowed to stand overnight at
ambient temperature. The reaction mixture was quenched
into 1.2M HCl (4 L) and the organic layer was washed with
water before being concentrated to a solid. Hexane (1.5
L) was added and the resulting slurry was cooled to 5C
and filtered. The filter cake was washed with cold hexane
and air dried to afford 440 g of crude product (73% yield)
which was used directly in the next step.
D.N. 4723A
-25- 133~592
c) 4-Bromo-2,5-difluorobenzoyl chloride.
A total of 2075 R (8.79 moles) of crude
4-bromo-2,5-difluorobenzoic acid from step (b) was treated
with thionyl chloride (2.0 L), and the resulting slurry
was slowly heated to reflux (90C internal) to obtain a
solution. After removal of excess thionyl chloride, the
product was collected at 85-95C (oil pump, vacuum not
measured), leaving a solid residue. The distillate
afforded 2045 g (91%) of a liquid which was used directly
in the next step.
d) Ethyl 4-bromo-2,5-difluorobenzoylacetate [V; Alk = Et,
X = Br, X = Fl.
A solution of monoethyl malonate (800 g, 6.06
moles) and 3 R of 2,2'-bipyridyl (indicator) in tetrahy-
drofuran (11.0 L) was cooled in a Dry Ice/acetone bathwhile adding n-butyllithium in hexane (7.50 L, 1.6M) until
a reddish color persisted for several minutes at -15C.
The reaction mixture was then cooled to -60C and
4-bromo-2,5-difluorobenzoyl chloride (785 g, 3.07 moles)
was added over a 1-1/4 hour period. Stirring was contin-
ued for 1/2 hour before quenching the reaction into 16
L of lN hydrochloric acid. The organic layer was washed
with 2 x 10 L of water, 2 x 6 L of 10% aqueous sodium
bicarbonate, and then 2 x 10 L of water. Concentration
of the organic layer to dryness afforded an oil which
crystallized on cooling. The concentrates from three runs
(total of 8.0 moles) were combined and recrystallized from
6 L of hexane to give a first crop of 1505 g (61.5%) and
a second crop of 220 g (9.0%).
D.N. 4723A
- 1334~92
-26-
e) Ethyl 3-(cyclopropylamino)-2-(4-bromo-2,5-difluorobenz-
oyl)acrylate [VIII; Alk = Et, X = Br, X' = F].
A solution of ethyl 4-bromo-2,5-difluorobenzoyl-
acetate (1224 g, 4.0 moles) and N,N-dimethylformamide
dimethyl acetal (630 ml, 4.8 moles) in 2.5 L of tetrahy-
drofuran was heated at reflux for 2-1/2 hours and then
stirred overni~ht at ambient temperature. The solvent
was removed under reduced pressure and the residue was
triturated with hexane to remove excess N,N-dimethylform-
amide dimethyl acetal. The solvent was decanted off. Theresidue was dissolved in 2.5 L of tetrahydrofuran and
cooled to 5C. Cyclopropylamine (305 ml, 4.4 moles) was
added over a 1/2 hour period. The solvent was removed
by vacuum distillation and the residue was used directly
in the next step.
f) Ethyl l-cyclopropyl-7-bromo-6-fluoro-1,4-dihydro-4-
oxo-3-quinolinecarboxylate [II; Alk = Et, X = Br].
To the ethyl 3-(cyclopropylamino)-2-(4-bromo-
2,5-difluorobenzoyl)acrylate prepared above (assumin~ 4.0
moles) was added N,N-dimethylformamide (2.5 L) and potas-
sium carbonate (736 g, 5.3 moles). The mixture was heated
to 90C on a steam bath, at which time an exothermic reac-
tion started raising the temperature to 115C over 5
minutes. A thick precipitate formed. The reaction was
then stirred at ambient temperature and the solids were
collected at 50C. The filter cake was washed with N,N-
dimethylformamide, then slurried in 10 L of water and
D.N. 4723A
-27- 133:~592
refiltered. The off-white solids were washed with water
and dried. The crude product was purified by recrystalli-
zation from 20 volumes of methylene chloride and repeated
rework of second and third crops. From 1585 g of crude
product a total of 1270 g of purified material was
obtained in 80% recovery.
g) 2,6-Dimethyl-4-(tributylstannyl)pyridine.
A 22 L flask was charged with 740 g of 4-bromo-
2,6-lutidine and 10.0 L of diethyl ether and cooled to-
-60C in a Dry Ice/acetone bath under nitrogen. A solu-
tion of 4.0 moles of n-butyllithium was added dropwise
over 1 hour maintaining a temperature below -58C to form
an orange-yellow precipitate. After continued stirring
in the cold for 15 minutes, 1280 g of tributyltin chloride
was added over 2 hours at a temperature of -60 to -57C
to form a solution. The reaction was stirred cold for
45 minutes before it was slowly (2 hours) warmed to 20C.
A portion of Super-Cel (100 g) was added and the reaction
mixture was filtered to remove the precipitated lithium
chloride. The cake was washed with diethyl ether (2 x
500 mL). After concentration to dryness a total of 1575
g (99.7~/O yield) of product was obtained which was used
without further purification.
r~ J'J'?~l t~ ~
D.N. 4723A
133~592
-28-
h) Ethyl l-cyclopropyl-7-(2,6-dimethyl-4-pyridinyl)-6-
fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylate [I; Alk
= Et, R' and R" = H].
A mixture of ethyl l-cyclopropyl-7-bromo-6-fluo-
ro-1,4-dihydro-4-oxo-3-quinolinecarboxylate (500 g, 1.42
mole), 2,6-dimethyl-4-(tributylstannyl)pyridine (617 g,
1.56 mole) and dichlorobis(triphenylphosphine)palladium
(28 g, 3 molar %) in 400 ml of N,N-dimethylformamide was
slowly heated to 150C in a nitrogen atmosphere and main-~
tained at that temperature for one hour. It was cooled,
dissolved in 3 L chloroform and stirred with 2 L of water
for 15 minutes. The two-phased solution was filtered
through a bed of Super-Cel, and the organic layer was
separated and dried over anhydrous magnesium sulfate. The
solvent was removed under reduced pressure and the residue
was stirred with 3 L of ether for 25-30 minutes. It was
filtered and washed with more ether (2 L). The solids
were air dried inside the hood to give 430 g (80%) of
product, used directly in the next reaction.
i) 1-Cyclopropyl-7-(2,6-dimethyl-4-pyridyl)-6-fluoro-1,4-
dihydro-4-oxo-3-quinolinecarboxylic acid [I; R, R' and
R" = H]-
A suspension of ethyl l-cyclopropyl-7-(2,6-di-
methyl-4-pyridpl)-6-fluoro-1,4-dihydro-4-oxo-3-quinoline-
carboxylate (430 g, 1.13 mole) and sodium hydroxide (115g, 2.87 moles) in 5 L water was stirred on a steam bath
for 4 hours resulting in a clear solution. The hot solu-
D.N. 4723A
133~592
-29-
tion was treated with charcoal (20 g) and filtered. The
yellow filtrate was cooled to room temperature and washed
once with 3 L ethyl acetate to remove nonacidic impuri-
ties. The aqueous layer was then stirred with excess
acetic acid (240 ml) at 60-70C for one hour. The white
solid was filtered hot, washed with 2 L of water and dried
at 60-70C under vacuum for 24 hours to afford 363 ~ (91%)
of crude product. This material was crystallized from
8 L of N,N-dimethylformamide to yield 340 g (93.6%) of
faint yellow product, m.p. 300-301C, identical with the
product of Examples l(i) and 2(f).
Example 4
a) 4-Bromo-2,3,5,6-tetrafluorobenzoic acid [X].
n-Butyllithium (42 ml, 2.4M in hexane) was
slowly added to a solution of 30.78 g 1,4-dibromo-2,3,-
5,6-tetrafluorobenzene in 200 ml tetrahydrofuran cooled
to -70C under nitrogen. Solid carbon dioxide (about 12
g) was then added to the stirred mixture which was then
allowed gradually to warm to 0C at which point 16 ml 6M
hydrochloric acid and 16 ml water were added. The reac-
tion mixture was concentrated and the residue extracted
with methylene dichloride. The extract was washed with
concentrated sodium chloride solution, dried (magnesium
sulfate) and concentrated to dryness to give 22.23
(81~5~/o) 4-bromo-2,3,5,6-tetrafluorobenzoic acid, m.p.
128-135C.
D.N. 4723~
133~592
-~n
b) 4-Bromo-2,3,5,6-tetrafluorobenzoylchloride [XI].
A mixture of 21.83 g 4-bromo-2,3,5,6-tetraflu-
orobenzoic acid and 16.7 g phosphorus pentachloride was
stirred at room temperature for about three days. The
reaction mixture wa~ then distilled under aspirator vacuum
to give 20.44 g (88%) of the acid chloride.
c) Ethyl 4-bromo-2,3,5,6-tetrafluorobenzoylacetate [XII;
Alk - C2H5].
n-Butyllithium (192 ml, 2.4M in hexane) was
slowly addet to a stirred solution of 30.24 g monoethyl-
malonate and 15 mg 2,2'-bipyridine in 500 ml tetrahydro-
furan cooled to -60 to -70C under nitrogen. After about
half of the butyllithium had been added, the temperature
of the mixture was raised to -20 to -25C at which tem-
perature the remainder of the butyllithium was added. Thereaction mixture was then recooled to -60 to -70C and
33.41 g 4-bromo-2,3,5,6-tetrafluorobenzoyl chloride in
10 ml tetrahydrofuran was added. The reaction mixture
was allowed to warm to room temperature, stirred
overnight, and then poured into 460 ml lM hydrochloric
acid. The organic layer was separated, dried (magnesium
sulfate) and concentrated. The residue was dissolved in
ether, washed with aqueous potassium bicarbonate solution,
dried (magnesium sulfate), concentrated and distilled to
give 34.18 g ethyl 4-bromo-2,3,5,6-tetrafluorobenzoylace-
tate, b.p. 112-117C (0.8 mm.).
D.N. 4723~
- 1334592
d) Ethyl 2-(4-bromo-2,3,5,6-tetrafluorobenzoyl)-3-dimeth-
ylaminopropenoate [XIII; Alk - C2Hs].
Dimethylformamide dimethylacetal (11.85 g) was
added to a solution of 33.63 g ethyl 4-bromo-2,3,5,6-tet-
rafluorobenzoylacetate in 100 ml tetrahydrofuran cooledin an ice-bath. The reaction mixture was then immersed
in a warm water bath in order to drive it to compietion.
The resulting solution was used directly in the next reac-
tion.
] e) Ethyl 2-(4-bromo-2,3,5,6-tetrafluorobenzoyl)-3-cyclo-
propylaminopropenoate [XIV; Alk 2 C2H5].
The solution from part (d) above was cooled in
an ice-bath, and 7 ml cyclopropylamine was added. The
reaction mixture was concentrated, the residue dissolved
in 550 ml hot absolute ethanol, and the product allowed
to crystallize upon cooling to give 31.66 g ethyl
2-(4-bromo-2,3,5,6-tetrafluorobenzoyl)-3-cyclopropylamino-
propenoate, m.p. 167-168.5C (79% yield from ethyl
4-bromo-2,3,5,6-tetrafluorobenzoyl acetate).
f) Ethyl 7-bromo-1-cyclopropyl-5,6,8-trifluoro-1,4-dihy-
dro-4-oxo-3-quinolinecarboxylate lII; R' and R" - F, Alk
- C2H5 ] .
Potassium carbonate (30 g) was added to a
stirred solution/suspension of 31.65 g ethyl 2-(4-bromo-
2,3,5,6-tetrafluorobenzoyl)-3-cyclopropylaminopropenoate
in 300 ml dimethylformamide. The mixture was heated at
150C for 1.5 hours, then cooled, poured into water and
D.N. 4723A
-~2- 133~59~
extracted with methylene dichloride. The extract was
washed with water and sodium chloride solution, dried
(magnesium sulfate) and concentrated. The residue W88
recrystallized from acetonitrile to give 19.3 g (64%)
ethyl 7-bromo-1-cyclopropyl-5,6,8-trifluoro-1,4-dihydro-
4-oxo-3-quinolinecarboxylate, m.p. 187-189C.
g) l-Cyclopropyl-7-(2,6-dimethylpyridinyl)-5,6,8-triflu-
oro-1,4-dihydro-4-oxo-3-guinolinecarboxylic acid ~I; R
- H, R' and R" ~ F].
A mixture of 2.8 g ethyl 7-bromo-1-cyclopropyl-
5,6,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylate,
2.2 g 2,6-dimethyl-4-(trimethylstannyl)pyridine (Example
1, part 8), 2 ml hexamethylphosphoramide, 320 mg dichloro-
bis(triphenylphosphine)palladium and 50 ml dioxane was
~tirred and heated under reflux in an argon atmosphere
for 24 hours. The reaction mixture was concentrated to
dryness and the residue was treated with 100 ml of lN
hydrochloric acid and heated at reflux for 2 hours. The
latter mixture was filtered and the filtrate concentrated
to dryness. The residue was dissolved in 50 ml 5% aqueous
potassium carbonate, decolorized with charcoal and fil-
tered. The filtrate was acidified with concentrated
hydrochloric acid, sodium acetate added, and the resulting
precipitate was collected, dried and recrystallized from
ethanol to give 1.6 g 1-cyclopropyl-7-(2,6-dimethylpyri-
dinyl)-5,6,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecar-
boxylic acid as a cream-colored solid, m.p. 264-266C.
D.N. 4723A
_33_ 1334~92
Example 5
a) Ethyl l-cyclopropyl-6,8-difluoro-7-(2,6-dimethyl-4-
pyridinyl)-5-(benzylthio)-1,4-dihydro-4-oxo-3-quinoline-
carboxylate [I; R - C2Hs, R' ~ C6HsCH2S, R" 8 Fl.
Sodium hydride (1 R, 60% in oil) was added
portion-wise to a mixture of 7.39 g ethyl l-cyclopropyl-
7-(2,6-dimethyl-4-pyridinyl)-5,6,8-trifluoro-1,4-dihydro-
4-oxo-3-quinolinecarboxylate (Example 4, part R) and 2.1
ml benzylthiol in 250 ml tetrahydrofuran cooled in an
ice-bath. After the addition of sodium hydride wss
complete, thin layer chromatography indicated that start-
inR material still remained; therefore, an additional 0.2
ml benzylthiol and 0.1 g sodium hydride were added. The
reaction mixture was washed with water and sodium chloride
solution, and the aqueous layer was extracted with ethyl
acetate. The combined organic extracts were dried (sodium
sulfate) and concentrated. The residue was suspended in
hexane and the solid product recovered (7.0 g). The
latter was taken up in isopropyl acetate - methylene di-
chloride (1:1) and chromatographed on silica using iso-
propyl acetate. The first product eluted (2.27 R, yellow
solid, m.p. 184-186C) was identified as ethyl 5,8-bis-
(benzylthio)-l-cyclopropyl-7-(2,6-dimethyl-4-pyridinyl)-
6-fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylate. The
second product eluted (2.12 g, pale yellow solid, m.p.
190-195C) wa~ identified as the desired ethyl l-cyclo-
propyl-6,8-difluoro-7-(2,6-dimethyl-4-pyridinyl)-5-(ben-
zylthio)-1,4-dihydro-4-oxo-3-quinolinecarboxylate.
D.N. 4723A
1334592
-34-
b) EthYl l-cyclopropyl-6,8-difluoro-7-(2,6-dimethyl-4-
pyridinyl)-1,4-dihydro-4-oxo-3-quinolinecarhoxylate [I;
R = C2Hs, R' = H, R" = Fl.
RaneY nickel (10 R, wet) was rinsed with abso-
lute ethanol and added to a susPension of 2.12 ~ ethyll-cyclopropyl-6,8-difluoro-7-(2,6-dimethyl-4-pYridinyl)-
5-(benzylthio)-1,4-dihydro-4-oxo-3-quinolinecarboxylate
in 100 ml of absolute ethanol. The mixture was heated
at reflux for 15 min., then filtered and concentrated.-
The residue was chromatoRraphed on silica ~el usin~ ethylacetate to Rive 1.0 ~ ethyl 1-cyclopropYl-6,8-difluoro-7-
(2,6-dimethyl-4-pyridinyl)-1,4-dihydro-4-oxo-3-quinoline-
carboxylate, m.p. 186.5-187C.
c) l-Cyclopropyl-~$,8-difluoro-7-(2,6-diDlethyl-4-Pyridin-
yl)-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid ~I; R
and R' = H, R" = Fl.
A suspension of 1.0 ~ ethyl 1-cyclopropyl-6,8-
difluoro-7-(2,6-dimethyl-4-pyridinyl)-1,4-dihydro-4-oxo-3-
quinolinecarboxylate in 20 ml lM hydrochloric acid was
heated at reflux for 2 hours. The reaction mixture was
cooled, poured into saturated sodium acetate and extracted
with ethyl acetate. The extract was dried (sodium sul-
fate) and concentrated, and the residue (0.84 R) was
recrystallized from absolute ethanol to ~ive 0.70 R
1-cyclopropyl-6,8-difluoro-7-(2,6-dimethyl-4-pyridinyl)-
1,4-dihydro-4-oxo-3-~uinolinecarboxylic acid, colorless
needles, m.p. 246-248.5C.
A sample of the foreRoin~ acid was converted
to its sodium salt, obtained in the form of a yellow
powder, m.p. above 300C.
D.N. 4723~
133~S92
Example 6
a) Ethyl l-cyclopropyl-6,8-difluoro-7-(2,6-dimethyl-4-
pyridinyl)-5-(phenylthio)-1,4-dihydro-4-oxo-3-quinoline-
carboxylate lI; R = C2Hs, R' = C6HsS, R" = F] was prepared
from 7.50 8 ethyl 1-cyclopropyl-7-(2,6-dimethyl-4-pyridin-
yl)-5,6,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarbox-
ylate, 1.95 ml thiophenol and 0.92 sodium hydride in 190
ml tetrahydrofuran according to the procedure of Example
5, part (a), and was obtained in 80% yield as a light
]0 yellow solid, m.p. 230-231C (from acetonitrile).
b) Ethyl l-cyclopropyl-6,8-difluoro-7-(2,6-dimethyl-4-
pyridinyl)-1,4-dihydro-4-oxo-3-quinolinecarboxylate [I;
R = C2Hs, R' = H, R" = Fl was prepared from 2.5 g ethyl
l-cyclopropyl-6,8-difluoro-7-(2,6-dimethyl-4-pyridinyl)-
5-(phenylthio)-1,4-dihydro-4-oxo-3-quinolinecarboxylate
and 25 g Raney nickel in ethanol according to the proce-
dure of Example 5, part (b), and was obtained in 86%
yield, m.p. 185-187C, identical with the product of Exam-
ple 5, part (b).
c) 1-Cyclopropyl-7-(2,6-dimethyl-4-pyridinyl)-6,8-diflu-
oro-5-(phenylthio)-1,4-dihydro-4-oxo-3-quinolinecarboxylic
acid [I; R - H, R' - C6HsS, R" = Fl was prepared by
hydrolysis of ethyl 1-cyclopropyl-6,8-difluoro-7-(2,6-
dimethyl-4-pyridinyl)-5-(phenylthio)-1,4-dihydro-4-oxo-3-
quinolinecarboxylate with hydrochloric acid according tothe procedure of Example 5, part (c), and was obtained
in the form of a light-yellow solid, m.p. 246.5-247.5C
(from acetonitrile).
D.N. 4723A
-36- 133~592
Example 7
l-Cyclopropyl-7-(2,6-dimethyl-4-pyridinyl)-6-fluoro-1,4-
dihydro-4-oxo-8-(benzylthio)-3-quinolinecarboxylic acid
[I; R and R' = H, R" = C6HsCH2S] was obtained by treatment
of ethyl 5,8-bis(benzylthio)-1-cyclopropyl-7-(2,6-dimeth-
yl-4-pyridinyl)-6-fluoro-1,4-dihydro-4-oxo-3-quinoline-
carboxylate (the byproduct obtained in Example 5, part
a) with Raney nickel according to the procedure of Example
5, part (b), followed by hydrolysis of the resulting ester-
with hydrochloric acid according to the procedure ofExample 5, part (c), and was obtained as a colorless
solid, m.p. 207-208C when recrystallized from ethanol.
Example 8
a) 2,3,4,5-Tetrafluorobenzoyl chloride.
Thionyl chloride (2.9 L), 2.5 kg 2,3,4,5-tetra-
fluorobenzoic acid and 14.5 ml dimethylformamide were
charged to a 12 L reaction vessel and warmed at 90-95C
for about 90 minutes. The excess thionyl chloride was
first removed at atmospheric pressure, then in vacuo. The
residue was distilled on a steam bath at water pump
pressure collecting the fraction with b.p. 65-70C at
about 15 mm resulting in 2635 g (96.2%) of pale yellow
distillate.
D.N. 4723A
13345g2
-37-
b) Ethyl 2,3,4,5-tetrafluorobenzoylacetate.
In a nitrogen atmosphere a 50 gallon kettle was
charged with 50.9 kg of tetrahydrofuran, 5.2 kg of mono-
ethyl malonate and about 5 g of 2,2'-dipyridyl. After
cooling the mixture to -36C, 41.6 kg of n-butyllithium
(15% in hexane) was added over 3 hours maintaining the
temperature at -25 to -35C. The resultant slurry was
cooled further to -60C and then treated over about 50
minutes with the acid chloride of part (a) at -62 to
-54C. The green/yellow mixture was stirred for 2 hours
at ambient temperature and allowed to warm further over-
night. The mixture (-24C) was quenched (vacuum) into
ambient dilute hydrochloric acid (15 L of muriatic acid
and 61 L of deionized water). The quench mixture was
separated and the organic phase was washed with 2 x 40
L of deionized water. The combined aqueous phases were
back extracted with 40 L of hexane-ether (1:1). All
organic layers were combined and washed with 100 L of
saturated sodium bicarbonate solution; again back extract-
ing the aqueous phase with 40 L of hexane-ether (1:1).
The combined organic layers were concentrated to an oil
in vacuo followed by dissolution in 20 L of hexane and
repeated concentration to dryness. The hot oil was
finally dissolved in 19 L of hexane. The solution was
cooled to -5C and the crystallized solids were filtered
using 4.8 L of cold (-6C) hexane as wash. The material
was dried in vacuo at room temperature affording 4234 g
D.N. 4723A
1334S92
-38-
of product suitable for use in the next step. A second
crop was obtained by concentrating the combined filtrate
and wash and cooling to low temperature. The combined
yield for the first and second crops was 4841 g (74.9a/O).
c) Ethyl l-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-
3-quinolinecarboxylate [XV; Alk = Et].
A 12 L stirred flask was charged with 4.8 L of
tetrahydrofuran, 1584 g of ethyl 2,3,4,5-tetrafluorobenz-
oylacetate and 834 ml of dimethylformamide dimethyl
acetal. After establishing a nitrogen atmosphere, this
mixture was heated to reflux for`l hour and then stirred
at ambient temperature for four hours. The mixture was
cooled and maintained at 4-5C while adding 438 ml of
cyclopropylamine over a period of 35 minutes. It was then
stirred at 3-5C for 1 hour and concentrated in vacuo.
The yellow crystalline solid was dissolved in 3.6 L of
dimethylformamide and 912 g of powdered potassium carbon-
ate was added with strong stirring. The slurry was then
heated on a steam bath for 1 hour (maximum internal
temperature was 108C for 5 minutes). The hot mixture
was poured into 30 L of cold water. Filtration, washing
first with 6 L of cold water and then 6 L of cold ethanol
followed by drying in vacuo at 50C gave 1615 g of product
(86.5% yield).
D.N. 4723A
-39- 133~592
d) Ethyl 7-azido-1-cyclopropyl-6,8-difluoro-1,4-dihydro-
4-oxoquinolinecarboxylate [XVI; Alk = Et].
Dimethylformamide (2638 ml), 807 g of the ethyl
cyclopropyl ester of part (c) and 177.3 g of sodium azide
were combined and heated in a 12 L flask at 90-95C for
2 hours. The resulting dark solution was allowed to cool
slightly. The solution was diluted (vacuo) with 9 L of
deionized water using an additional 8.7 L of deionized
water to wash and transfer the thick slurry. The crystal--
line solid was collected and washed with 6.0 L of deion-
ized water at room temperature. It was dried in vacuo
at 50-55C resulting in 809 g (93.4%) of tan material.
e) Ethyl 7-amino-1-cyclopropyl-6,8-difluoro-1,4-dihydro-
4-oxo-3-quinolinecarboxylate [YVII; Alk = Et].
A slurry of 1.20 kg of ethyl 7-azido-1-cyclo-
propyl-6,8-difluoro-1,4-dihydro-4-oxo-3-quinolinecarboxyl-
ate in 12 L of dimethylformamide was charged to a five
gallon autoclave. After placing the vessel under nitro-
gen, a slurry of 76 g of 10~/o palladium-on-carbon in 700
ml of dimethylformamide was added. The mixture was
hydrogenated at 48-50 p.s.i. and 600 r.p.m. for four
hours. The reaction mixture was filtered and concentrated
under aspirator pressure to give a thick but stirrable
dark residue. Ethanol (3 L) was added and the suspension
was briefly refluxed before allowing to cool. After cool-
ing to 5C, the product was collected, washed with 2 x
500 ml of cold ethanol and then dried at 65-70C in vacuo
overnight to give 962 g (86.7%) of product.
D.N. 4723A
1334592
-40-
f) Ethyl 7-bromo-1-cyclopropyl-6,8-difluoro-1,4-dihydro-
4-oxoquinoline-3-carboxylate ~XVIII; Alk = Et].
A 22 L flask was charged with 960 ~ of ethyl
7-amino-1-cyclopropyl-6,8-difluoro-1,4-dihydro-4-oxo-3-
quinolinecarboxylate, 8.7 L of acetonitrile and 835 R ofcupric bromide and heated to 70C. N-Butyl nitrite (545
ml) was added over 30 minutes and the reaction mixture
was heated at reflux for 2 hours. It was concentrated
in vacuo until about 6 L of distillate was collected. The
concentrate was poured into 19 L of 2 molar hydrochlo-
ric acid to form a precipitate. After stirring for 30
minutes the product was collected and washed with 4.0 L
of deionized water, 12 L of 3.75 molar ammonium hydroxide
and finally with an additional 12 L of deionized water.
After drying in vacuo at 60C a total of 984 g (85.1%)
of crude bromo compound was obtained. The crude product
was dissolved in refluxing methanol and cooled slowly to
2C. The solids were collected, washed with 2 x 350 ml
of cold methanol and dried in vacuo at 50-55C to afford
a first crop of 598.5 g (60.8%).
g) Ethyl l-cyclopropyl-6,8-difluoro-1,4-dihydro-7-(2,6-
dimethyl-4-pyridinyl)-4-oxo-3-quinolinecarboxylate [I;
Alk = Et, R' = H, R" = F].
A 5 L flask was charged with 590 g of ethyl
7-bromo-1-cyclopropyl-6,8-difluoro-1,4-dihydro-4-oxo-3-
quinolinecarboxylate, 689 g of 2,6-dimethyl-4-(tributyl-
stannyl)pyridine, 33.6 g of dichlorobis(triphenylphos-
D.N. 4723A
- 13~459~
-41-
phine) palladium catalyst and 375 ml of dimethylformamide
under nitrogen, and heated slowly until the reaction beRan
to exotherm at 130C. At 140C the heater was removed
and the temperature rose to 155C. After the exotherm
had subsided, the solution was heated at reflux for one
hour. The cooled reaction mixture was dissolved in a
chloroform (3.2 L)-water (2.6 L) mixture and filtered
through Super-Cel to remove the spent catalyst. The
filter cake was washed with 2 x 500 ml of chloroform and-
1.0 L of water. The lower organic layer was separatedand dried over magnesium sulfate. The drying agent was
filtered and washed with 500 ml of chloroform. The fil-
trate was concentrated in vacuo to form a crystalline
solid which was slurried in 3.5 L of hexane. The solid
was collected and washed with more hexane (700 ml) and
reslurried in 2.6 L of ether. The product was finally
filtered, washed with 2.0 L of ether and air dried under
a hood to give 512 g (80.7% yield) of product.
h) l-Cyclopropyl-7-(2,6-dimethyl-4-pyridyl)-6,8-difluoro-
1,4-dihydro-4-oxo-3-quinolinecarboxylic acid [I; R and
R' = H, R" = F].
A suspension of 550 g of the ester of part (g)
in 7.0 L of 1 molar hydrochloric acid was stirred on a
steam bath for 2.5 hours to give a clear solution. The
hot solution was treated with 30 g of charcoal and
filtered. The yellow filtrate was cooled to room tempera-
ture and washed once with 3.0 L of chloroform to remove
D.N. 4723A
133~592
-42-
non-basic impurities. The aqueous layer was diluted with
L of water, made strongly alkaline with 35/O sodium
hydroxide (pH 11-12) and warmed on a steam bath to 40C
for two hours. At the end of this period an excess of
acetic acid (280 ml) was added and the reaction mixture
was warmed to 60-70C on a steam bath for 4-6 hours. It
was cooled to 40C and filtered, washed with 4 L of- water
and the white solid was dried at 65-70C for 24 hours
under vacuum to give 397 g (78%) of crude product. The
crude product from four batches was combined and the total
solids (1038 g) were crystallized from a mixture of 2.5
L of chloroform and 5.5 L of ethanol. Two crops were
collected to give 980 g (94/O) of pure product, identical
with the product of Example 5(c).
The in vitro antimicrobial activity of the
compounds of the invention was determined by a microplate
dilution procedure. Bacterial cultures were grown in
Meuller Hinton II (cation supplemented) broth (S. aureus,
_. faecalis, M. luteus, E. coli and P. aeruginosa), Brain_ _ _
Heart Infusion (BHI) broth supplemented with 10% heat
inactivated horse serum (S. pneumoniae) or BHI broth
supplemented with 5 mcg/ml Hemin and 0.5 mcg/ml vitamin
K (B. fragilis) at 37C for 18-24 hrs. The cultures were
produced under aerobic conditions with the exception of
B. fragilis which was grown 48 hrs. under anaerobic
conditions (atmosphere 5~/O C02, 10% H2 and 85% N2).
Resulting suspensions were diluted 1/10 in the appropriate
broth or used undiluted for the inoculum. Aqueous
, D.N. 4723A
133~592
solutions of the compounds of the invention were
solubilized in dimethylsulfoxide (DMS0) at the desired
concentration and 200 mcl were dispensed into the first
row of wells of a sterile microplate. The compounds were
then serially diluted two-fold in DMS0 to give a working
stock concentration range plate. The last row of wells
was left compound-free receiving only DMS0 to serve as
a growth control. Five mcl from each well of the working
stock plate was transferred to corresponding wells of a
separate plate containing 95 mcl/well of the appropriate
broth. All dilutions were made with either an automated
dilutor or manually. The wells of microplate containing
the desired compound concentrations and compound-free
growth controls in broth were then inoculated using the
MIC 2000 inoculator which delivers 1.5 mcl/well to give
a final inoculum level of 104 microorganism/well or 105
microorganism/ml. Plates were incubated as described
above and read for visible growth. The minimal inhibitory
concentration (MIC: expressed in mcg/ml) of each compound
tested against each test microorganism was determined as
the lowest concentration of compound which prevents
visible microbial growth.
D.N. 4723A
1334592
-44-
The followin~ compounds were tested according
to the foregoing procedure:
A. l-Cyclopropyl-7-(2,6-dimethyl-4-pyridinyl)-
6-fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid
(Examples li and 2f).
B. l-Cyclopropyl-7-(2,6-dimethyl-4-pyridinyl)-
5,6,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic
acid (Example 4h).
C. l-Cyclopropyl-6,8-difluoro-7-(2,6-dimethyl-
4-pyridinyl)-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid
(Example 5c).
Prior art compounds:
P. 7-(2,6-Dimethyl-4-pyridinyl)-1-ethyl-1,4-
dihydro-4-oxo-3-quinolinecarboxylic acid.
Q. l-Cyclopropyl-6-fluoro-7-(1-piperazinyl)-
1,4-dihydro-4-oxo-3-quinolinecarboxylic acid.
R. 7-(2,6-Dimethyl-4-pyridinyl)-1-ethyl-6-flu-
oro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid.
The following Table I summarizes the results
of the testinR of the foregoing compounds:
~ D.N. 4723A
~45- 1334592
TABLE I
In vitro (mc~/ml)
ML EC SA SF SP PA BF
Compound MIC MICMIC MIC MIC MIC MIC
5A 0.5 0.030.008 0.06 0.03 2 0.5
B 0.5 0.1250.008 0.06 0.03 8 0.5
C 0.25 0.060.008 0.06 0.016 4 - 0.125
__________________________________________________________
P8 0.25 0.25 1 2 32 16
Q2 0.004 0.25 0.5 0.25 0.125 2
10 R0.5 0.06 0.03 0.25 0.25 4 2
ML = Micrococcus luteus
EC = Escherichia coli
SA = Staphylococcus aureus
SF - Streptococcus faecalis
15 SP = Streptococcus pneumoniae
PA - Pseudomonas aeruRinosa
BF - Bacteroides fraRilis
It will be seen from the above Table that
the compounds of the invention (A, B, C) are substantially
more active than the prior art compounds (P, Q, R) against
all of the organisms except E. coli and P. aeruginosa,
and except M. luteus in the case of compound R. The
improvement in activity is particularly marked in the
case of the important pathogen Staph. aureus, where
compounds A, B and C are thirty times as active as
compounds P and Q and four times as active as compound
R.
D.N. 4723A
1334~2
-46-
The in vivo antibacterial activity of the
compounds of the invention was determined in female
mice, 18-20 grams each. Aqueous solutions of the
compounds to be tested were prepared by dissolvin~ the
free acid form in dilute sodium hydroxide and diluting
the solution with distilled water to the desired
concentration.
Cultures of E. coli were ~rown in brain heart
infusion broth, and the mice were inoculated intra-
peritoneally with 0.5 ml of the bacterial test inoculumsuspended in ~aline. Cultures of Staph. aureus were
thawed from frozen pooled stocks and mixed with 5% mucin.
A 0.5 ml preparation was used to infect mice by i.p.
inoculation.
The mice were medicated subcutaneously (sc)
or orally (po) with 0.5 ml of the test compound solution
one-half hour postinfection. Deaths were recorded daily
for seven days. Fifty percent protective dose values
(PDso) were calculated using probit analysis. The results
are given in the following Table II.
TABLE II
In vivo (Mouse, mR/k~
Staph. aureu8 (PD50) E, coli (PD50)
Compound sc po sc po
A 0.08 0.20 3.1 3.8
B 0.08 0.14 8.9 10.8
C 0.06 0.09 ,6.1 5.7
__________________________________________,________________
P 2.37 3.8 13.5 17.9
Q 1.16 5.9 0.09 0.57
R 0.71 1.38 5.39 8.24
D.N. 4723A
- 13345g2
It will be seen from the above Table II that,
althou~h the compounds of the invention (A, B, C) are
about equal in activity to compounds P and R and less
active than compound Q against E. coli, the new compounds
are markedly more active (9-30 times) than the prior
art compounds against Staph. aureus.
In monkeys, compounds A and C gave high and
prolonged serum levels after 25 mg/kR oral dosing.
Compound A showed a maximum concentration of 1311g/ml
at 7 hours with a half-life of 13 hours; and compound
C showed a maximum concentration of 34~1g/ml at 5.5 hours
with a half-life of 20 hours.
The compound of Example 6(c), 1-cyclopropyl-7-
(2,6-dimethyl-4-pyridinyl)-6,8-difluoro-5-(phenylthio)-
1,4-dihydro-4-oxo-3-quinolinecarboxylic acid, also was
found to have appreciable antibacterial activity in
vitro, MIC (~/ml) values as follows: M. luteus (16.0),
Staph. aureus (1.0), Strep. faecalis (16.0), Strep.
pneumoniae (2.0), and B. fraRilis (16.0).
The compound of Example 7, 1-cyclopropyl-7-
(2,6-dimethyl-4-pyridinyl)-6-fluoro-1,4-dihydro-4-oxo-8-
(benzylthio)-3-quinolinecarboxylic acid, also was found
to have appreciable antibacterial activity in vitro,
MIC (~/ml) values as follows: M. luteus (64.0), E. coli
25 (4.0), Staph. aureus (<0.125), Strep. faecalis (2.0),
Strep. pneumoniae (2.0) and B. fraRilis (64.0).
D.N. 4723A
- 1334~92
-48-
The compounds of the invention can be prepared
for use by conventional pharmaceutical procedures; that
is, by dissolving or suspending them in a pharmaceutically
acceptable vehicle, e.g., water, aqueous alcohol, glycol,
oil solution or oil-water emulsion, for parenteral or
oral administration or topical application; or by incorpo-
ratin~ them in unit dosage form as capsules or tablets
for oral administration either alone or in combination
with conventional adjuvants or excipients, e.R. calcium-
carbonate, starch, lactose, talc, magnesium stearate,gum acacia, and the like.
TLJ:BE
7-11-88
