PRODUCTION DE 1-ALKOXYCARBONYL-2-ALKOXY-1,2-DIHYDROQUINOLINES

PROCESS FOR THE PREPARATION OF 1-ALKOXYCARBONYL-2-ALKOXY-1,2-DIHYDROQUINOLINES

Abrégé anglais

PROCESS FOR THE PREPARATION OF 1-ALKOXYCARBONYL-2-
ALKOXY-1,2-DIHYDROQUINOLINES
Abstract of the Disclosure
The preparation of 1-alkoxycarbonyl-2-alkoxy-1,2-
dihydroquinolines is carried out by the reaction of
quinoline with a chloroformate and an aliphatic
alcohol at a temperature of from -10°C to 20°C and
a pH of 7 to 10 in the presence of an inert organic
diluent which is insoluble or only sparingly soluble
in water.

Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the preparation of a 1-alkoxycarbonyl-2-alkoxy-1,2-
dihydroquinoline of the formula
<IMG>
in which
R1 represents a primary or secondary alkyl group containing 1 to 6 carbon
atoms; an alkoxy alkyl group containing 1 to 3 carbon atoms in each alkyl
group, a cycoalkyl group containing 3 to 8 carbon atoms or an aralkyl group
containing 1 to 4 carbon atoms in the alkyl group and
R2 has the same meaning as R1 or represents a tertiary alkyl group; an
alkyl thioethyl group; an alkane sulphonyl ether or a cyanoalkyl group,
by the reaction of quinoline with an aliphatic chloroformate and an aliphatic
alcohol, in which quinoline is reacted with a one- to ten-times excess of an
alcohol of the formula
H-OR2
in which R2 has the meaning specified above, and with not more than the
stoichiometric quantity of a chloroformate of the general formula
<IMG>
in which R1 has the meaning specified above, at a temperature of from -10 to
20°C and a pH of 7 to 10 in the presence of an aqueous inorganic neutralising
agent.
2. A process as claimed in claim 1 in which R1 and/or R2 represents an
alkyl group with 1 to 6 carbon atoms.
14

3. A process as claimed in claim 2 in which R1 and/or R2 represents
a methyl, ethyl, n-propyl, isopropyl, n-butyl, sec. butyl or iso-butyl group.
4. A process as claimed in claim 1 in which R1 and/or R2 represents
a 2-alkoxymethyl or 2-alkoxyethyl group.
5. A process as claimed in claim 1 in which R1 and/or R2 represents a
cyclopentyl or cyclohexyl group.
6. A process as claimed in claim 1 in which R1 and/or R2 represents a
benzyl or phenethyl group.
7. A process as claimed in claim 1 in which R2 represents a tertiary-
butyl or tertiary-amyl group.
8. A process as claimed in claim 1 in which R2 represents a methyl
thioethyl or ethyl thioethyl group.
9. A process as claimed in claim 1 in which the alcohol of formula
H-OR2 is an aliphatic primary or secondary alcohol containing 1 to 6 carbon
atoms; ethylene glycol monoalkyl ether containing 1 to 3 carbon atoms in the
alkyl group; a cycloalkanol containing 3 to 8 carbon atoms or an aryl
carbinol containing 1 to 4 carbon atoms in the chain.
10. A process as claimed in claim 1 in which the quinoline is reacted
with a four to ten times excess of alcohol.
11. A process as claimed in claim 1 which is carried out in the presence
of an inert organic solvent which is insoluble or only sparingly soluble in
water.
12. A process as claimed in claim 11 in which the solvent is an inert
hydrocarbon, ketone, ester or ether.
13. A process as claimed in claim 12 in which the solvent is a
chlorinated hydrocarbon.

14. A process as claimed in claim 13 in which the solvent is
dichloromethane or 1,2-dichloroethane.
15. A process as claimed in claim 1 in which the neturalising agent is
an aqueous solution or suspension of an alkali metal carbonate or bicarbonate.
16. A process as claimed in claim 15 in which the neutralising agent is
an aqueous solution or suspension of sodium or potassium carbonate or
bicarbonate.
17. A process as claimed in claim 1 in which the reaction is carried out
at a temperature of from -10 to 10°C.
18. A process as claimed in claim 17 in which the reaction is carried
out at a temperature of from -5 to +5°C.
19. A process as claimed in either of claims 2, 3 or 4 in which the
quinoline is reacted with a four to ten times excess of alcohol.
20. A process as claimed in either of claims 2, 3 or 4 which is carried
out in the presence of an inert organic solvent which is insoluble or only
sparingly soluble in water.
21. A process as claimed in either of claims 2, 3 or 4 which is carried
out in the presence of an inert organic solvent which is insoluble or only
sparingly soluble in water, said solvent being chosen from the group
consisting of an inert hydrocarbon, a ketone, an ester or an ether.
22. A process as claimed in either of claims 2, 3 or 4 which is carried
out in the presence of an inert organic solvent which is insoluble or only
sparingly soluble in water, said solvent being a chlorinated hydrocarbon.
23. A process as claimed in either of claims 2, 3 or 4 which is carried
out in the presence of a solvent selected from the group consisting of
dichloromethane and 1,2 dichloroethane.
16

24. A process as claimed in either of claims 2, 3 or 4 in which the
neutralising agent is an aqueous solution or suspension of an alkali metal
carbonate or bicarbonate.
25. A process as claimed in either of claims 2, 3 or 4 in which the
neutralizing agent is an aqueous solution or suspension of sodium or
potassium carbonate or bicarbonate.
26. A process as claimed in either of claims 2, 3 or 4 in which the
reaction is carried out at a temperature of from -10° to 10°C.
27. A process as claimed in either of claims 5, 6 or 7 in which the
quinoline is reacted with a four to ten times excess of alcohol.
28. A process as claimed in either of claims 5, 6 or 7 which is
carried out in the presence of an inert organic solvent which is insoluble
or only sparingly soluble in water.
29. A process as claimed in either of claims 5, 6 or 7 which is carried
out in the presence of an inert organic solvent which is insoluble or only
sparingly soluble in water, said solvent being chosen from the group
consisting of an inert hydrocarbon, a ketone, an ester or an ether.
30. A process as claimed in either of claims 5, 6 or 7 which is carried
out in the presence of an inert organic solvent which is insoluble or only
sparingly soluble in water, said solvent being a chlorinated hydrocarbon.
31. A process as claimed in either of claims 5, 6 or 7 which is carried
out in the presence of a solvent selected from the group consisting of
dichloromethane and 1,2 dichloroethane.
32. A process as claimed in either of claims 5, 6 or 7 in which the
neutralising agent is an aqueous solution or suspension of an alkali metal
carbonate or bicarbonate.
17

33. A process as claimed in either of claims 5, 6 or 7 in which the
neutralizing agent is an aqueous solution or suspension of sodium or
potassium carbonate or bicarbonate.
34. A process as claimed in either of claims 5, 6 or 7 in which the
reaction is carried out at a temperature of from -10° to 10°C.
18

Description

3'~
The invention relates to a new process for the
preparation of l-alkoxysarbonyl-2-alkoxy-1,2-dihydroquinoline.
It is known t~ prepare l-alkoxycarbonyl-2-alkoxy-
1,2-dihydroquinoline by reacting quinoline with chloro-
formates in the presence of an alcohol and o~ a tertiary
amine as acld-binding agent, as is described in U.S. Patents
No. 3,389,142 and 3,452,140 and in the article by Muren und
Weissmann, J. Med. Chem. 14 (1971), 51 and Fieser & Fieser
"Reagents for organic syntheses" Volume 2, page 191.
One disadvantage of the known processes is that the
maximum yield which can be obtained is only 70 %, according
to Muren und Weissmann, which is i~su~ficient for economic
utilisation of the process.
It is an object of this invention to provide a process
for the preparation of 1-alkoxycarbonyl-2-alkoxy-1,2-dihydro-
quinoline from which higher yields can be obtained than in
the known processes and which makes it possible for the
compounds to be produced on a larger scale.
The invention relates to a process for the preparation
of 1-alkoxycarbonyl-2-alkoxy-1,2-dihydro~uinoline of the
general formula
1~ -OR2
O-,C-OR
in which
Rl represents a primary or secondary alkyl group with 1 to 6
carbon atoms which may be substituted by a nonionic group,
for example a methyl, ethyl, n-propyl, isobutyl, n-butyl,
A-~ 1308 - 2 - ~

~Q~321
sec. butyl or isobutly group, an alkoxyalkyl group containing 1 to 3
carbon atoms in each alkyl group, e.g. a 2-alkoxymethyl or 2-alkoxyethyl
group, a cycloalkyl group containing 3 to 8 carbon atoms, e.g. a cyclo-
pentyl or cyclohexyl group or an aralkyl group containing 1 to 4 carbon
atoms in the alkyl group, e.g. a benzyl or phenethyl group and
R2 may have the same meaning as Rl or may represent a tertiary alkyl group
such as a t-butyl or t-amyl group, an alkyl thioethyl group such as a
methyl thioethyl or ethyl thioethyl group, an alkane sulphonyl ether or
a cyanoalkyl group, in particular a cyanoethyl group, by the reaction of
quinoline with an aliphatic chlorocarbonic acid ester (i.e. a chlorofor-
mate) and an aliphatic alcohol, in which quinoline is reacted with a
one to ten-times excess of an alcohol of the formula
H - ~R2
in which R2 has the meaning specified above and with not more than the
stoichiometric quantity of a chloroformate of the general formula
Cl - C - OR
lo
in which Rl has the meaning speciied above at a temperature of from -10C
to 20C and a p~l of 7 to 10 in the presence of an aqueous inorganic neutral-
ising agent and if desired in the presence of an inert organic diluent which
is insoluble or only sparingly soluble in water.
The aliphatic alcohols used as starting materials for the process
according to the invention are all available commercially. Lower aliphatic
primary alcohols and the corresponding secondary alcohols, ethylene glycol
monoalkyl ether, lower cycloalkanols and lower aryl carbinols are particularly
suitable. The process is in principle, also
~ l - 3 -

~07~
suitable for higher alcohols but the products obtained from
them cannot be puri.fied by ~is~illation ~ithout great
difficulty ~nd considerable loss of yield. Alcohols
containing prima:ry, secondary or tertiary amino groups are
unsuitable for thc process.
The chloroformates used as starting
materials are either available commercially or prepared, for
examyle, by the reaction of phosgene with a suitable alcohol
or as described in E.H. Ro~ Chemistry of Carbon Compounds"
Volume 1, part B "Aliphatic Compounds", pages 833 and 886
to 899, Elsevier Publishing Company, New York, N.Y. (1952) or
in Houben-Weyl, Volume 8, pages lOl et. seq. Information
about many of these compounds may be found in "Chemical
Abstracts" in which they are indexed as esters lmder the
heading "Formic acid, chl.oro-".
In contrast to the previous1y known processes for the
prcparation of l-alkoxycarbonyl-7-alkoxy-l,2-dihydroquinolines,
whlch are all carried out with strict exclusion of water,
the reaction according to the inventi.on is carried out in an
aqueous organic medium, preferably in a diphasic aqueous
organic medium, although in certain cases, the advantageous
results of the invention can also be obtained in a monophasic
medium with a relatively low water content.
It has been found particularly advantageous to introduce
the quinoline into the reaction vessel together with a multiple
excess of the alcohol used as its reactant and an inert
organic solvent in contact with an aqueous solution or
suspension of the inorganic neutralising agent which should
have a pH of from 7 to lO, and to add the chlorocarbonic
acid ester to this reaction mixture
The presence of a large excess of alcohol, in general
four to ten times the stoichiometric quantity for the reaction,
A-G 1308 _ 4 _

~7 ~3~i
prevents the formation of any significant quantities of
2-llydroxy-1-alkoxy-carbonyl_1,2-dihydroquinoline which is
an unwanted product and extremely sensitive to hydrolysis.
If too large an excess of alcohol is used, however, too
much water is introduced into the organic phase where it
gives rise to side reactions, particularly if a lower
alcohol which is highly water-soluble is used. The optimum
~uantities of alcohol can easily be determined by simple
tests.
Organic solvents or diluents are only required if
exceptionally highly water-absorbent alcohols such as methanol,
methyl glycol or ethyl glycol ~re used.
The solvents or diluents use~ may be inert hydrocarbons,
e.g. chlorinated hydrocarbon~such as dichloromethane or
1,2-dichloroethane, ketones or e~ters, or al~o ethers wh~ h
have a low water absorption capacity. The b~st result~ are
~ener~lly obtained with dichloromethane.
The neutralising agent~ used are most suitably aqueous
~olution~ or suspensions of alkali metal carbonates or
alkali metal bicarbonates such as sodium or pota~sium
carbonate or bicarbonate. Carbonates have the advantage o~
retaining m~re water in the aqueous phase, particularly if they
are used at higher concentrations and in excess. On the
other hand, i~ bicarbonates are u~ed as neutralising agents,
generally in an excess o~ 20 to 100~ by weight, based on
the chloroformate, the resulting reaction is easier to
control and leads to purer products. Above all, bicarbonates
suppress the troublesome formation of 2-hydroxy compoundsO
Since the hydroxy compound is relatively stable under the
reaction conditions, it is not removed until the product is
isolated, and at that stage it either prevents crystallisation
or causes breakdown of the vacuum used for distillation due to
A-G 1308 - 5 _

1C~7~321
thermal decomposition to guinoline, alcohol and carbon
dioxide when alkoxy carbonyl-alkoxy dihydroquinolines, which
are high-bolling compounds when pure, are purified by
distillation
The advantages of the process according to the invention,
compared with the previously known processes are immediately
apparent if no water is added to the reaction mixture or only
toward~ the end of the reaction. In that case, neutralisation
of the hydrogen chloride liberated proceeds too slowly and
traces of hydrogen chloride cause losses in yield when the
product is isolated.
The use of an exces~ of quinoline, generally from
2 to 40 oh by weight, compared with the chloroformate
is advantageous but not essential. In special cases,
a quinoline exce~s may also be replaced by corresponding
quantities of a volatile tertiary amine such Q9 triethylamine
a~ auxlllary base.
~he reactlon temperature ~hould generally be from
-10C to 10C, more preferably from -5C to 5C, but may be
higher if less reactive chloroformates are u~ed.
Above 20C, the yields drop drastically. The use of
catalysts, e.g. Lewis acid~ ~uch as zinc chloride, boron
trliluoride or ferric chloride is not necessary and, in most
cases, even harm~ul because it renders the product~ of the
process unstable.
It i~ presumed that the reaction gives ri~e to an
extremely short-lived l-alko~ycarbonyl quinolinium ion in
the organic phase, and that this ion i~ scarenged by the
addition of alcohol. The hydrogen chloride liberated is
initially taken up by iree quinoline ~nd then ab~orbed by
the neutrali~ing agent of the aqueou~ phase.
The proce~s according to the invention is ~uitable
A-G 1308 - 6 -

~07~3Z'l
among other things for the preparation of certain dihydro-
~uinoline derivatives which have been described as
tranquillisers in US Patent Specifications No. 3,389,142
and No. 3,452,140.
The process according to the invention may also be used
for the preparation of most of the 2-alkoxy-1,2-dihydro-
quinoline-l-carboxylic acid esters which have been described
. as hardeners for protein-containing layers in Belgian Paten
B j Specification No. 816 41V,(U.Y.. nppl. Mo. ~7851/7~ .
The process according to the invention will now be
more fully described in the following examples.
A-G 1308 - 7 -

3'~
Example 1
l-methoxycarbonyl-2-methoxy-1,2-dihydroquinoline
,H
I OCH3
C=O
~CH3
1.1: 180 g of potassium carbonate (1.3 mol) in 120 ml
of water are added to a solution of 160 of quinoline (1.24
mol) in 200 ml of methanol and 400 ml of dichloromethane and
cooled to between -2C and 2C. 94.5 g (1 mol) of methyl
chloroformate are added dropwise with stirring at 0C and
the reaction mixture is warmed to 25C. The organic phase
is separated from the pasty sediment of salt, washed twice
with 200 ml portions of water, dried over solid sodium
carbonate, concentrated by evaporation and distilled under
vacuum. After the first runnings consistine of quinoline
(b.p. 80 to 90C), the vacuum deteriorates while an
intermediate fraction is distilled off. The main product
then distils over at a temperature of 140 to 150C and
3 to 4 Torr.
The yield was 146 g of viscous oil which was 67 % of the
theory.
1.2: 94.5 g of methyl chloroformate are added dropwise
with stirring at 0C to a suspen5ion of 120 g (1.43 mol) of
sodium bicarbonate in 300 ml of methanol, 300 ml of dichloro-
methane, 132g of quinoline (1.02 mol) and 40 ml of water.
The temperature of the mixture is raised to 25C. 800 ml of
water are added and the organic phase is separated, washed
twice with 200 ml portions of water and dehydrated over solid
potassium carbonate. It is then concentrated by evaporation
at reduced pressure and distilled under vacuum. The vacuum
A-~ 1308 - 8 -

10 ~3~1~
t3 mm) remains constant after the quinoline ~20 g) has
be~n distilled off.
The yield was 172 g which was 78 /0 of the theory and the
product had a bp3mm ~ 140 to 150C
1.3: The procedure is -the same as in method B but using 160 g
fo quinoline (24 /0 excess) instead of 132 g.
First runnings: 45 g of quinoline
Main fraction: 176 g (80 o~ of the theory), bp3mm: 138 - 150 C-
Example 2l-methoxycarbonyl-2-ethoxy-1,2-dihydroquinoline
yl
OC2H5
0=C-OCH3
~15
94,5 g (1 mol) of methyl chloroformate are added dropwise
witll stirrin~ at 0C to a suspension of 120 g of sodium
~icar,l)onate in 300 ml of ethanol, 132 g of quinoline (1.02
mol) and 40 ml of water. The temperature i9 kept at 0C for
one hour more and the crystalline product is then precipitated
with 600 ml of ice water. The precipitate is suction-
filtered, washed with 500 ml of water and dried in a vacuum.
The yield was 19~ g, which was ~5 ~ Or the theory and the
melting point after crystallisation from Ligroin was 72 to 74C.
Example 3
l-methoxycarbonyl-2-isopropQxy-1,2-dihydroquinoline
CH3
0-CH ~CH
3 b
~ 7 /~ \
~_~ i O OCH3
A-~ 130~ - 9 -

10~ 3~1
94.5 g (1 mol) of methyl chloroformate are added dropwise
with stirring t~- a ~uspension of 120 g of sodium bicarbonate
(1.43 mol) in 30() ml of isopropanc,l, 300 ml of dichloromethane,
132 g of quinoline (1.02 mol) and 40 ml of water. The
reaction temperature is kept at O to 10C by cooling. Stirring
is continued for one more hour at 5C and tlle mixture is then
heated to 25C. 600 ml of water are added and the organic
phase is separated llf~ washed twice with 200 ml portions
of water, dehydrated over solid pota~sium carbonate,
concentrated by evaporation under vacuum and left to
crystallise. 50 ml of Ligroin are then added and the product
is ~uction-filtered.
The yield was 200 g which was 81 % of the theory, and th0
product had a melting poin1; of 48 to 50c.
Example 4
l-methoxycarbonyl-2-(2-methoxy)ethyl-1,2~dihydroquinoline
H
, l O-cH2~H2-ocH3
/~
O OCH3
94.5 g (1 mol) of methyl chloroformate are added dropwise
with stirring at n to 5C to a suspension of 120 g (1.43 mol)
of sodium bicarbonate in 300 ml of methyl glycol, 300 ml of
dichloromethane, 160 g of quinoline (1.24 mol) and 40 ml of
water. The temperature is kept at 10C for a further 2 hours
and the reaction mixture is then warmed to 25 C, 500 ml of
water are added and the organic phase is separated off and
washed twice with 200 ml portions of water. After dehydration
over solid potassium carbonate, the product is concentrated
by evaporation at reduced pressure and distilled under vacuum.
After a first runnings of about 50 g of quinoline and a short
A-G 1308 - 10 -

3'~
intermediate fraction, 196 g (74.5 ~ of the theory) distil
over at 175 to 195C and 3 to 4 Torr without breakdown of
the vacuum.
Example 5
l-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline ~EEDQ~
1~ C2H5
//c
C2H5
5.1: 300 ml of ethanol and 132 g of quinoline (1.02 mol)
are added to 110 g of potassium carbonate (0.8 mol) in 90 ml
of water. 10~.6 g ¦1 mol) of ethyl chlorocarbonate are added
dropwise at 0 to 3C with vigorous stirring. The temperature
is then kept at 0 to 5C for 1 hour more before the product
is prscipitated by the addition of 500 ml of ice water.
The precipitate i9 suction-filtered and recrystallieed from
00 ml of methanol.
The yield was 210 g which was 85 ~ of the theory and the
product had a melting point of 62 to 64C.
5.2: Method A is repeated except that instead of potassium
carbonate, ~ suspension of 120 g of sodium bicarbonate in
60 ml of water is used as neutralising agent.
The yield was 227 g which was 92 ~ of the theory melting and
the product had a melting point o~ 62 to 64C.
5.3: (comparison experiment) The procedure is the same as
in method A except that instead of potassium carbonate, 50 g
(1.25 mol) of sodium hydroxide in 40 ml of water is used
as neutralising agent. An oily product which consists for
the most part of quinoline and does notcrystalliee is obtained.
5.~: (comparison e~periment) The procedure is the same as
in method A except that the reaction is carried out without
A-G 1308

~7~
water. 190 g of a semi-solid product are obtained, irom
which 90 to 120 g of solid sub~tance can be isolated by
cry~talli~ation from ligroin.
5.5: (comparison experiment):
2-ethoxy-1-(2H)-quinoline carboxylic acid ethyl ester:
10.8 g (0.10 mol) o~ ethyl chloroformate are added dropwi~e
to 12.9 g (0.1~ mol) oi quinoline under nitrogen. The
mixture iB stirred for 1 hour at O to 7C. A white precipitate
forms, which di~solves when a ~olution of 12.9 g (0.10 mol)
of dii~opropyl ethylamine in 5(~ ml of absolute alcohol i~
added. The ~olution is then warmed up to room temperaturé and
evaporated to drynes~ under vacuum. 200 ml of cyclohexane are
added to the re~idue, followed b~ 200 ml oi ice water, and
the organic pha~e iB dehydrated over magnesium ~ulphate.
22.5 g oi a pale yellow oil are obtained aiter evaporation
of the solvent. Vacuum di~tillation yield~ 16.9 g of
colourle 8~ compound with a boiling point of 115 to 118C
(0,1 mm). The oily liquid ~olldliie~ when left to ~tand.
The melting polnt was 64 to 68C (irom llgroin)
5.6: (comparl~on experlment):
A. Preparation oi 2-hydroxy-N-carbethoxy-1,2-dlhydroquinollne
and di-(N-curbethoxy-1,2-dihydro-2-quinolyl)-ether
~ -OH
o=c-o-cH2cH3
and
~_o ~3
CH3CH2-o-C=o ~=C-O-CH~CH~
3o
A solution o~ 240 g Or pota~ium hydroxide in 400 ml oi
water a~d 1600 g o~ ice i~ added over a period o~ 5 minute~
A-G 1308 - 12 -

~V~
with vigorous stirring to a solution, which has been cooled
to 15C~ of 220 g (2.0 mol) of ethyl chloroformate,
260 g (2.0 mol) of quinoline and 600 ml of dimethyl formamide.
When the mixture has been stirred for a further 10 minutes,
it is extracted with 1 litr0 of methylene chloride and the
organic phase is washed with water, dehydrated over anhydrous
magnesium sulphate, filtered and evaporated. 400 g of a
pale-brown liquid containing 2-hydroxy-N-carbethoxy-1,2-
dihydroquinoline, di-(N-carbethoxy-1,2-dihydro-2-quinolyl)
ether and quinoline are obtained (product A).
200 g of the oil are concentrated by distillation at
a bath temperature below 100C to remove unreacted quinoline.
125 g of a residue containing 2-hydroxy-N-carbethoxy-1,2-
dihydroquinoline and di-(N-carbothoxy-1,2-dihydro-2-quinolyl)-
ether are obtained (product B).B. Preparation of N-carbethoxy-2-ethoxy-1,2-dihydroquinoline
O=J-O-CH2CH3
A solution oi 120 g of product B, 100 ml of absolute
alcohol, 500 ml of anhydrou~ diethyl ether and 10 drop~ of
borotrifluoride etherate i9 stirred for 5 hours at 20 C.
80dium
The ethereal ~olution i~ wa~hed with saturated ~icarbonate
~5 solution and water, dehydrated over magnesium sulphate,
filtered and concentrated. An oil is obtained ~rom which 47 g
of the colourle~s compound N-carbethoxy-2-ethoxy-1,2-dihydro-
quinoline are obtained by distillation. The product had a
boiling point of 125 to 128C at 0.1 mm. The product
~olidifies when le~t to stand and had a melting point of 56
to 57C.
~-~ 1308