Note: Descriptions are shown in the official language in which they were submitted.
76
The present invention relates to a proce~ for ~he preparation of a hy~
droxylamine of the formula
A: R3 or ~: RNHOH
11 ~ 14
R ~ s
NHOH
In co~pound A, the group3 R1, ~2, R~, R4 and Rs each represent a hydrogen
atom, a hydroxy group, 8 halogen atom9 a llnear or branched-chain alkyl
group having 1 to 20 carbon atom~, an alkoxy group havlng 1 to 20 carbon
atoms, a cyclopentyl group, a cyclohexyl group9 a phenyl group, a phenyl~
alkyl or alkylphenyl group~ the alkyl group having 1 to 6 carbon atoms, or
wherein t~o of the groups R1, R2, R3, R4 or Rs attached to ad~acent carbun
atoms of the benzene ring together with the two carbon atoms of the benzené
rlng to which they are attached form a second benzene ring which is ortho-
condensed with the first benzene ring. In compound B, the group R represents
a linear or a brsnched-chain and/or cyclic alkyl group having l to 24 carbon
atoms.
In so far 8S the Groups R1, - Rs or R arc hydrocarbon containing group~,
they may have unsaturated bonds and may comprise substituents and groups
such as amino, hydroxylamino, amido, cyano, hydroxy alkoxy, carboxyl, oxy-
carbonyl, carboxy, sulphoxlde and ~ulphone. The groups R1 - R S or R may be
combined to form part of a polymerlc structure.
The aromatic hydroxylamine A can be obtained by hydrogenation of the corre-
~ponding nitro derivative in the presence of an inert ~olvent, a platinum
cataly~t and ~ tri- or penta valent organ1c pho~phorous compound.
Such a process is known from Ch~m. Abstract~, 91, (1979~, 56604W, wherein i~
referred to Japane~e patent publication no. 7924837.
~0``1~
2 ~
Although a nitrogen contalning base 19 formed a3 a byproduct of the hydro-
genation, due to a too rapid reduction of the~de~ired intermediate hydroxyl-
amine~ there wa~ proposed for a long time to carry out ~he hydrogenation in
the presence of an amount of an organic base to be added ~o the starting
reaction mixture, llke in eg. US Patent Speciflca~ion 3927101. Hereln it l
~tated that in order to obtain sufficien~ly high yield~ of hydroxyla~ines,
the ratio by weigh~ of the organic base to the nitro compound should be
greater than O.l:l, preferably between 0.5:l and 5:1,
Further di~closed is that the use of ~he base in trace amount~ does not
make it po~sible to stop the hydrogenation at the hydroxylamlne stage.
After the hydrogenation reaction i9 completed, the organic base has to be
removed. It has been observed that by using the above-mentioned high
amount3 of organic bsse, problems might arlse upon isolating the hydrDxyl-
amine.
It ha~ now been found that equivalent and even higher yields of hydroxyl-
amine can be obtained with a pro2ess of ths above ~ype which is charactPr-
ized in that the nitrogen-contsining base is added to the starting reaction
mixture in an a~ount of le~3 than lOV~o by weight, calculated on ths a~ount of
the nitro derlvative
It has been found that if only use i9 made of the phosphoruY compound or
the nltrogen-contalning base in an amoun~ of les~ than 10~/o by weight, cal-
culated on the amount of nitro derlvative, the ylelds of isolated hydro-
xylamine~ are significantly reduced in comparison with those obtained
with the process in ~he present invention.
It should be added that Japanese patent publication No.30.096/82 discloses
the use of trivalent pho3phorus compounds in reactions of the present
type. However, this publication does not mention the present combination
with the nitrogen-containing base in the starting reaction mixture.
Furthermore 9 U.S. 3 441 610 describes the catalytic hydrogenation of
nitroalkanes to N-alkyl-hydroxylamineR. Use is made of a recovered pal-
ladium catalyst and a cation of iron, nickel or cobalt in a two-phase
liquid syste~ of aqueous sulphu~ic acid and an immi~cible organic solvent.
In such an acidic medium the 10~9 o catalyst will be considerable and the
equipment may be subject to ~evere corrosion. Those dlsadvantages are cir-
cumvented by the present inve~tion.
. \
6'76
The present invention rela~es to a process or the ~elective catalytic
preparation of hydroxylamines with the structure A or B by selectlve
cata].ytic hydrogenation of corresponding n-itro derivatives.
The problem known for a long tlme as associated with the use of platlnum-
containing catalysts~ 1~ to preve~t tha nitro derivative~ from belng reduced
to amines in the hydrogenatlon stage. The present process provlde~ such a
proce3s without di~playing tlle di3advantages of similar, well-known proces-
s~s.
-3~ 314 R
As organic phosphorus compound tri- Of pentavalent compounds can he used.
Trivalent phosphorus compounds are preferred. A class of suitable phos-
phorus compounds includes trivalent compounds having aryl or arvloxy
groups which may be substituted or not.
Preferably the aryl and aryloxy groups are phenyl and phenyloxy groups. As
Examples of phosphorus compounds of this class may be mentioned triphenyl-
phosphite~ dimethylphenylphosphite, triphenylphosphine, triphenylphospho-
nite, tri-p-chlorophenylphosphonite, tri-p-nitrophenylphosphonite and tri-
cresvlphosphonite.
Diphenylphosphite, di-p-chlorophenylphosphite, di-p-nitrophenylphosphite
and di-p-methylphenylphosphite are also suitable phosphorus compounds.
A very suitable class includes phosphorus compounds having a~kyl or alkoxy
group(s) containing l to 20 carbon atoms. Especiallv preferred are tri-
alkylphosphines and tri-akylphosphites, with the alkyl group contalning 1
to 20 carbon atoms. EYamples thereof are: trimethylphospi-ine, tri-ethvl-
phosphine, tri-isopropylphosphine, tri-butylphosphine, tri-octvlphosphine,
tri-octaùecylphosphine, trimethylphosphite, tri-ethylphosphite, tri-iso-
propylphosphite, tributylphosphite, trihexylphosphite, triheptyIphosphite,
tri-octylphosphite, trinonylphosphite, tridecylphosphite and trilauryl-
phosphite.
Most preferred thereof are compounds with alkvl groups having l to 6 car-
bon atoms, special preference being given to tri-ethylphosphite, tri-iso-
propvlphosphite and tributylphosphite.
Further phosphorus compounds which can be used in the present process are:
phosphorus trichloride, dimethylphosphochloridite, di-ethvlphosphochlor-
idite, and he.Yamethylphosphoroustri-amide. In the last two compounds the
functions of nitrogen-containing base and phosphorus compound are com-
bined. If such compounds are used, the amount of a further nitrogen base
may be reduced.
Of course, also mixtures of the above phosphorus compound can be used.
Generally, the reaction mixture should contain O.l to 5% by weight of the
phosphorus compound, calculated on the amount of nitro derivative, pre-
ferably 0 ? to 2.0/o and more particularly 0.3 to l.O~b by weight.
76
_4_ A(~ 4 R
Suitable nitro~en bases are ammonia, monoalkvlamineS, dialkylar~ines, tri-
Qlkylamines, monoalkanolamines, dialkanol amines, trialkanol amines, rnono-
, di- or tri-aryl amines, (poly)alkylene polyamines, pyrrolidine and
piperidine substituted or not with 1 or ~ alkyl groups having 1 to 4 car-
bon atoms and pyridines substituted or not with one or more alkyl, amino,phenylalkylamino, phenylamino or pyrrolidone groups. The ni.trogen base may
contain primary, secondary and tertiary alkyl and/or alkanol groups.
Generally, the above-mentioned unspecified alkyl and alkanol groups may
contain I to 20, preferably 1 to 6 and most preferably I to 4 carbon
atoms.
E~amples of mono-, di- and trialkylamines are: methvlamine, ethYlamine,
propvlamine, butylamine, pentylamine, hexylamine, hept-lamine, octylamine,
nonylamine, octadecylamine, dimethylamine, diethylamine, dipropylamine,
dipentylami.ne, dihexvlamine, diheptylamine, dioctylamine, didecylamine,
clidodecylamine, dioctadecylamine, trimethylamine, triethylamine, tripro-
pylamine, tri-isopropylamine, tributylamine, tripentylamine, trihe.Yyl-
amine, triheptvlamine, tri-octylamine, tri-2-ethylhe~ylamine, tridecyl-
amine and tri-octadecylamine.
Suitable mono-, di- and tri-alkanol amines are those having alkanol groups
containing 1 to ~0 and preferably 1 to ~ carbon atoms. Examples thereof
are ethanolamine, propanolamine, butanolamine, diethanolamine and tri-
ethanolamine.
Suitable mono-, di- and tri-arylamines are N,N-cliethvl-N-phenylamine,
N-ethyl-N,N-diphenvlamine, triphenyl.amine, tri-o-methylphenylamine, tri-
m-methylphenylamine, tri-p-methylphenylamine, tri-benzylamine, N-benzyl-
N,N-dimethylamine, N-benzyl-N,N-diethylamine, N-benzyl-~,N-di-isopropvl-
amine, N-benzyl-~,N-di-n-butylamine and N-benzyl-N,N-di-tert.-butylamine.
Suitable (poly)alkylene polyamines are ethylenediamine, diethylenetri
amine, triethylene tetra-amine, tetra-ethylene pentamine, penta-ethylene
he~amlne.
Pyrrolidine and piperidine as well as substituted pyrrolidines and piper
idines containing 1 or 2 alkyl groups with 1 to ~ carbon atoms can also be
used. Preferred examples thereof are pyrrolidine, piperidine and mono-,
di-, tri- and tetramethylpyrrolidines and piperidines.
;'76
Mos-t preferred are the pyridines substi-tuted or not
with one or more alkyl, amino, phenyl, alkylamino, phenylamino or
pyrrolidone groups, the alkyl groups containing preferably 1 to 6
carbon atoms.
Examples thereof are pyridine, N-methylpyridine, 2,6--
dimethylpyridine, ~-methylethyl pyridine, 4-aminopyridine, 4-
dimethylaminopyridine, 4-di-ethylaminopyridine, 4-dipropyl-
aminopyridine, 4-dibutylaminopyridine and 4-diphenylamino-
pyridine. Preference is given -to the dialkylamino pyridines,
particularly to 4-dimethylaminoipyridine.
of course, also mixtures of the above nitrogen bases
may be used. The reaction mixture should contain less than 10%
by weight of nitrogen base, calcula-ted on the amount o nitro
derivative, generally 0.05 to 5%, preferably o.l to 2% and more
particularly 0.2 to 1% of the nitrogen base.
The nitro derivative starting material has the formula
C: R~ or D: RN02
R
R~\R~
NO~
In compound C, the groups Rl, R2, R3, R4 and R5 each
represent a hydrogen atom, a hydroxy group, a halogen atom, a
:Linear or branched-chain alkyl group having 1 to 20, preferably 1
to 6, carbon atoms, an alkoxy group having 1 to 20, preferably 1
to 6, carbon a-toms, a cyclopentyl group, a cyclohexyl group, a
phenyl group, a phenylalkyl or alkylphenyl group, the alkyl group
having 1 to 6 carbon atoms, or wherein two of the groups Rl, R2,
R3, R4 or R5 attached to adjacent carbon atoms of the ben~ene
- 5 -
'7~
ring together with the two carbon atoms of the benzene ring which
is orthocondensed wi-th the first benzene ring. In compound D,
the group R represents a linear or a branched-chain and/or cyclic
alkyl group having 1 to 24 carbon atoms
1.0
~ - 5a -
--6~ 8~ 7~ ~C~I l9l4 R
.
In so far as the groups Rl - Rs or ~ are hydrocarbon containing groups,
they may have unsaturated bonds and may comprise substituents and groups
such as amino, a~ido, nitro, nitroso, cyano, hydroxy, alkoxy, carbonyl,
oxycarbonyl, carboxy, sulphoxide and sulphone. Ihe substituents may be
combined to form part of a polymer structure.
Examples of aromatic nitro-derivatives are nitrobenzene, o-nitrotoluene,
m-nitrotoluene, p-nitrotoluene, p-isopropylnitrobenzene, m-butylnitroben-
zene, 1,3-dimethyl-(2 or 4 or ;~nitrobenzene, 1,3,5-trimethyl-2-nitroben-
zene, 4-nitro-biphenyl, para chloro nitrobenzene and (1 or 2 or 3~nitro-
naphthalene. Preference i9 given to nitrobenzene.
E~amples of aliphati~ nitro compounds are nitroethane, nitropropane,2-metilyl-2-nitropropane, 9-nitro-9-methyl-1,6-decadiene.
The catalyst silould contain platinum and may or may not be deposited on a
support. Suitable carrier materials are carbon blacks, alumina, silica,
calcium carbonate, barium sulphate and the li~e.
When the platinum is on a carrier, the catalvst composition usually con-
tains 0.1 to 20, preferablv 1 to lO;o of platinum. These catalyst can be
prepared by methods well-known in the art. ~enerall~l the reaction mixture
contains 0.001 to 5~O, preferably 0.01 to 1% by weight of platinum, calcu-
lated on the amount of nitro derivative.
The hydrogenation reaction is usually carried out in the presence of aninert solvent. There is no limitation on the solvent used, provided that
it does not react with the hydroxylamine formed. Suitable solvents are
water, lower alcohols such as methanol, ethanol, propanol, isopropanol,
aromatic and aliphatic hydrocarbons such as toluene and hexane. Preference
is given to a lower alcohol. Mixtures of the ahove solvents can also be
used~ The reaction mixture preferably contains 5 to 80~o by weight of sol-
vent.
The selective hydrogenation reaction can be carried out at Ov to 150C,
30 preferably between 5 and 50C at a hydrogen pressure of 10 to 2000 kPa,
preferably 100 to 500 kPa.
,
The present invention will be illustrated with the following examples.
7~
~ CH 1~314 R
Exa~le 1
A solution of nitrobenzene (~4.6 g) in 80 ml of methanol is charged into a
600 ml autoclave; and 0.33 g of a catalyst based on platinum and carbon
black contalning 3% of platinum is added. 0.1 g of 4-dimethylamino pyri-
dine and 0.25 g of tributylphosphite are then added to the autoclave. Theautoclave is tilen sealed and deaerated using a vacuum pump. Next, hydro-
genation is carried out at 10C at 414 kPa for 3/4 ho-lrs after which time
the theoretical amount of i)ydrogen was absorbed. After filtration of the
Pt/C catalyst, the filtrate is evaporated bv using a rotarv evaporatnr
under vacuum at 45-5~C (bath temperature), after wllich the final traces
of the solvent are removed using an oil pump. There are obtained 20.3 g of
crude phenylhvdroxylamine. The crude material is then treate~ with 75 ml
of heYane, after which the mixtu}e is well agitated and filtered. Final-
ly, there are obtained 17.7 g of pure phenylhydro~ylamine lviel~ 81.2'h,
m.p. 81C, correct IR and NMR).
Comparative E~ample A
__ __ _
Using the following amounts of starting materials and similar conditions
as in Example 1, hydrogenation is carried oot in the absence of 4-dime-
thvlaminopyridine.
Nitrobenzene 12.3 g
Methanol 40 ml
Tri-ethvlphosphite 0.322 g
3`~ Pt/C 0-400 g
Pressure of Hvdrogen 414 kPa
Temperature 10 ~C
Time 1 3/4 hours
Finally, there are obtained 9.4 g of an oil which does not crystallize to
give phenylhydroxylamine. The same results were obtained by using 0.25 g
of tributylphosphite instead of triethylphosphite.
Comparfl~.ive Example B
Using the following amounts of starting materials and similar conditions
as in Example 1, hydrogenation is carried out in the absence of a trial-
kyl phosphite:
-8~ 3~ 76 ~(~1 19l4 R
. .
Nitrobenzene 24.6 g
Methanol 80 ml
4-dimethylaminopyridine 2 g
3% PtlC 0.4 g
Pressure of Hydrogen 414 kPa
Temperature 10 C
Time 11/2 hours
Finally, there are obtained 21 g of an oil which upon treatment with
hexane (100 ml? followed by cooling to -30C gives 10 g of cryst~lline
phenylhydroxylamine. (Yield 45.9'~, m.p. 80C).
E~ le 2
The effects of adding different combinations of phosphorus compound and
organic base was evaluated as follows: The general method was the same as
in Example 1, e~cept that the organic base and phosphorus component were
varied as given in the following table. For this experiment the hvdrogen
pressure was maintained at 212 kPa and the final reaction mi~ture ana-
lysed~ using gas liquid chromatography.
Table 1
_ _ _ _ _ _
Triethylphosphite I Productcomposition(g)
~ TEP) I Phe~y~ droxylamine~PHA)
20 I L,evel I Ba~e(g~ I Nitroben~ene I Aniline I PHA I `iO~ield
L ~ TEP) ~ ~ l l I ofP~ ¦
0.17 g I I ~-7 1 3-4 1 13.8 1 71
0.17 g I D~P O.OSI 0.4 1 2.2 1 18.8 1 87.7
1 0.17 g I D~P 0.1 1 1.3 1 1.9 1 17.6 1 85.2
25 1 0 17 g ¦ Pyridine 0.1 1 5.3 ~ 1.3 1 13.2 L 76
_ _ _ _ _ _ _ _ _ _ _ _ _
Triphenylphosphine
(TPP) _ l _ _ _ _
Level ¦ Base
I TPP
30 1 0.17 g I 1 4.4 1 1.1 114.2 1 78
L_17 g I DMAP ~ 2.3 11~ 6 1 _ 85 __L
D~AP = dimethylaminopyridine
_9~ CI~ 19l4 R
E~ample 3
Using the following amounts of starting materials and similar conditions
as in Example 1, hydrogenation is carried out as described before:
2-Nitrotoluene27.42 g
Methanol 80 ml
4-DMAP 0.1 g
Tributylphosphite 0.250 g
3% Pt/C 0.33 g
Pressure of hydrogen 212 ~Pa
Temperature 32 C
Time 4.0 hours
There are obtained 21.8 g of an oil, which upon treatment with hexane (lO0
ml) followed by cooling to about -30C gives 14.76 g of N-o-tolylhydro~yl-
amine ~Yield 60%, m.p. 44C, correct IR and NMR spectrum).
Example 4
Using the following amounts of starting materials and similar conditions
as in Example 1, hydrogenatioll is carried out as described before:
4-Nitrotoluene27.42 g
Methanol 80 ml
4-DMAP 0.1 g
Tributylphosphite 0.25 g
3%Pt/C 0.33 g
Pressure of Hydrogen 212 kPa
Temperature 25 C
Time 1 hours
There are obtained 24.5 g of an oil, which upon treatment with he~ane (100
ml) followed by cooling to about -30C gives 14.2 g of N-~p-tolyl)
hydroxylamine (Yield 57.7%, m.p. 98-99C, correct IR and NMR spectrum).
_~ample 5
Using the following amounts of starting materials and slmilar conditions
as in Example 1, hydrogenation is carried out a5 described before:
-'~ 7~ ~( H 1)14 R
p-chloro Nitrobenzene 31.51
Methanol 80 ml
4-DMAP 0.1 g
Tributylphosphite 0.25 g
3/~ Pt/C 0.33 a
Pressure of Hydrogen 414 kPa
Temperature25 C
Time 2 hours
There are obtained 25.2 g of an oil, which upnn treatment with he~ane (125
ml) followed by cooling to about -30~C gi-es 18.52 ~ of p-chloro phenyl-
hydroxylamine (YielA 64.5~, m.p. 83-84C, correct IR and N~ spectrum).
E~ample 6
~sing the following amounts of starting materials and similar conditions
as in e~ample 17 hydrogellation was carried out as described before:
15 l-Nitropropane17.82 g
triethylamine0.10 g
triethylphosphite 0.166 o
3~/~ Pt/C 0.33 g
pressure of hvdrogen 345 kPa
20 temperature 40 C
reaction timeabout 5l6 hours
Ihe crude mi~ture was filtered and Pt/C removed for :~ny subsequent use.
The organic layer was treated with conc. HCl and cooled below ambient tem-
perature where N-(1-propyl)hydro~ylamine hvdrochloride (1/.84g) was ob-
tained in 80`h yield.
E~am ~
~sing the following amounts of starting materials and similar conditionsas given in E~ample 1, the hydrogenation of 1-nitropropane, 2-nitropro-
pane, 2-methyl-2-nitropropane and 9-methyl-9-nitro-1,6-decadiene is car-
ried out as described before:
~ 7~ l4 ~
aliphatic nitro compound 0.2 mo:les
4-dimethylamino pyridine 0,1 g
tributyl phosphite 0,25 g
3:'h pt/C0,33 g
pressure of hydrogen 414 kPa
temperature40 C
reaction timeabout 3/4 hours
The crude material i~ treated with 75 ml ot hexane, followed by igorous
agitation and subseql~ent filtration. The yields ot ~-(l-propyl)hydro~vl-
amine, N-~2-propyl) hydro~ylamine, N-(~-methylprop~l) hvdroxylamine and
9-hydroxyl-amino-9-methvl-1,6-decadiene from 1-nitropropane, 2-nitropro-
pane, 2-methyl-2-nitropropane and 9-methyl-9-nitro-1,6-decadiene ~re ~0,
67, 67 and 60`io ~ respectively.
