GB2106508A

GB2106508A - Preparation of substituted ureas

Info

Publication number: GB2106508A
Application number: GB08220929A
Authority: GB
Inventors: Manmohan Singh Majhail
Original assignee: Quimco GmbH
Current assignee: Quimco GmbH
Priority date: 1981-07-31
Filing date: 1982-07-20
Publication date: 1983-04-13
Also published as: FR2512816A1; JPS5829758A; BR8204494A; GB2106508B; DE3228821A1

Abstract

A process is disclosed for the preparation of substituted ureas of the general formula:- <IMAGE> in which R is a hydrogen atom or an unsubstituted or substituted aliphatic, cycloaliphatic, aryl or heterocyclic radical and R1 and R2, which may be the same or different, are unsubstituted or substituted, straight- chained or branched aliphatic radicals, general formula:- <IMAGE> in which R has the same meaning as above, is reacted with a thiolcarbamate salt of the general formula:- <IMAGE> in which R1 and R2 have the same meanings as above.

Description

SPECIFICATION Process for the preparation of substituted ureas The present invention is concerned with a new and improved process for the preparation of substituted ureas.

Our British Patent Specification No. 1,380,258 describes and claims a method of purifying secondary ammonium N,N-disubstituted thiolcarbamates of the general formula:

in which R' and R", which may be the same or different, are unsubstituted or substituted aliphatic radicals or in which R' and R" together represent an unsubstituted or substituted divalent aliphatic radical, wherein a solution of a secondary ammonium N,N-disubstituted thiolcarbamate of the abovegiven general formula in a solvent, which solution also contains impurities, is co-distilled to give a distillate containing the desired thiolcarbamate in the solvent.The thiolcarbamate can be prepared, for example, by reacting a secondary amine of the general formula R'.NH.R", in which R' and R" have the same meanings as above, in a solvent either with carbon monoxide and sulphur or with carbonyl sulphide.

Our British Patent Specification No. 1,431,654 describes and claims a process for preparing a trisubstituted urea of the general formula.

R"'(NH.CO.NR'R")n in which R"' is an unsubstituted or substituted mono-, di- or polyvalent aromatic radical, R' is an unsubstituted or substituted monovalent aliphatic or aromatic radical and R" is an unsubstituted or substituted monovalent aliphatic radical or R' and R" together represent an unsubstituted or substituted divalent radical in which at least one of the two carbon atoms adjoining the nitrogen atom of the urea is aliphatic, and n is an integer, wherein an aromatic nitro compound of the general formula R(NO2)n or an aromatic nitroso compound of the general formula R(NO)n is reacted with a secondary ammonium N,N-disubstituted thiolcarbamate of the general formula.

or with a mixture of a secondary amine of the general formula R'.NH.R" and carbon monoxide and sulphur, carbon monoxide and hydrogen sulphide or carbonyl sulphide or with a mixture of a secondary ammonium sulphide or hydrogen sulphide of the general formula o O (R'R"NH2)2S or R'R"NH2.SH and carbon monoxide.

Furthermore, according to our co-pending British Patent Application No. 8029950, there is provided a process for the preparation of substituted ureas of the general formula:

in which R is an aryl radical, which optionally contains other substituents, for example halogen atoms, straight-chained and branched aliphatic hydrocarbon radicals containing up to 10 carbon atoms, alkoxy radicals, trifluoromethyl radicals, sulphonylmethyl radicals and the like, and R1 and R2 which can be the same or different, are aliphatic radicals containing up to 18 carbon atoms, wherein a nitroaryl compound of the general formula R.NO2, in which R has the same meaning as above, is reacted in an inert solvent at an elevated temperature and pressure with sulphur, carbon monoxide, a secondary amine of the general formula R,.NH.R2 and a tertiary amine of the general formula R1.N(R2)R3, in which R1, R2 and R3, which can be the same or different, are aliphatic radicals containing up to 1 8 carbon atoms.

It is an object of the present invention to provide a new process for the preparation of substituted ureas.

Thus, according to the present invention, there is provided a process for the preparation of substituted ureas of the general formula:

in which R is a hydrogen atom or an unsubstituted or substituted aryl radical and preferably an unsubstituted or substituted phenyl radical or an unsubstituted or substituted aliphatic, cycloaliphatic or heterocyclic radical and R, and R2, which may be the same or different, are unsubstituted or substituted, straight-chained or branched aliphatic radicals, wherein a formyl compound of the general formula:

in which R has the same meaning as above, is reacted with a thiolcarbamate salt of the general formula:

in which R, and Rz have the same meanings as above.

The reaction mechanism believed to be involved may be illustrated, by way of example, by the following equation:-

The reaction may be carried out in an inert solvent, for example an aromatic solvent, such as benzene or a substituted benzene, or a cycloaliphatic, heterocyclic or aliphatic solvent. Specific examples of appropriate solvents include benzene, monochlorobenzene, dichlorobenzene, toluene, xylenes, naphthalene and tetrahydrofuran.

The reaction is preferably carried out at the reflux temperature of the reaction mixture. The end product can be obtained by stripping off volatiles and, if desired, purified by washing with and/or crystallising from an appropriate solvent.

The process of the present invention provides a simple and elegant method of producing substituted ureas, for example the known herbicidal compounds fenuron (N-phenyl-N',N'dimethylurea) and diuron (N-(3,4-dichlorophenyl)-N',N'-dimethylurea).

The following Examples are given for the purpose of illustrating the present invention: Example 1 N,N-Dimethyl-N'-phenylurea 50 g. Formanilide (IV) were boiled under reflux for 4 hours with 90 g. dimethyl ammonium N,Ndimethyl thiolcarbamate salt (V) in monochlorobenzene. Volatiles were then stripped off, leaving a pale solid which was washed with petroleum ether to give 63.5 g. (94% of theory) of N,N-dimethyl-N'phenylurea; m.p. 134-1 350C.

Example 2 N,N-Dimethylurea 22.5 g. (0.5 mol) Formamide were dissolved in 100 ml. monochlorobenzene. 90 g. Dimethyl ammonium N,N-dimethyl thiolcarbamate salt were added and the mixture was refluxed for 50 minutes.

Unreacted salt was recovered and then the monochlorobenzene solution was concentrated to give an almost quantitative yield (43.5 g.) of N,N-dimethylurea in the form of colourless crystals; m.p. 1 89- 1910C.

Example 3 N,N,N'-Trimethylurea 14.75 g. (0.25 mol) N-methylformamide were mixed with 50 g. dimethyl ammonium N,Ndimethyl thiolcarbamate salt and with 100 ml. monochlorobenzene. The mixture was refluxed for 2 hours and unreacted salt then recovered. The monochlorobenzene solution was concentrated under reduced pressure to give a molten mass which crystallised upon cooling. 24.3 g. N,N,N'-trimethylurea (95% of theory) were obtained; m. 74-750C.

Example 4 N,N-Dimethyl-N'-(4-chlorophenyl)-urea 25 g. (0.16 mol) 4-Chloroformanilide were mixed with 40 g. dimethyl ammonium N,N-dimethyl thiolcarbamate salt. 1 50 ml. Monochlorobenzene were added and the mixture was refluxed for 3 hours.

Unreacted salt was recovered by distillation and the monochlorobenzene solution was concentrated.

Upon cooling, fine colourless crystals separated out. The crystals were washed with a little cold monochlorobenzene and then with petroleum ether (b.p. 60-800C.) to give a crop of 29.8 g. (93.7% of theory) of N,N-dimethyi-N'-(4-chlorophenyl)-urea; m.p. 1 74--1 C.

Example 5 N,N-Dimethyl-N'-(3,4-dichlorophenyl)-urea 25 g. (0.13 mol) 3,4-Dichloroformanilide were mixed with 30 g. dimethyl ammonium N,Ndimethyl thiolcarbamate salt and 200 ml. monochlorobenzene. The mixture was refluxed for 3.5 hours and then worked up as in Example 4 to give a first crop of 28.6 9. (94.4% of theory) of light coloured crystals of N,N-dimethyl-N'-(3,4-dichlorophenyl)-urea; m.p. 1 58-1 600 C.

Example 6 N,N-Dimethyl-N'-(3-chloro-4-methylphenyl)-urea 25 g. (0.147 mol) 3-Chloro-4-methyl formanilide were reacted in a manner analogous to that described in Example 4 to give a first crop of 28.2 g. (919/0 of theory) of N,N-dimethyl-N'-(3-chloro-4methylphenyl)-urea; m.p. 147-149 0C.

Example 7 N,N-Dimethyl-N'-(3-trifluoromethylphenyl)-urea 25 g. (0.13 mol) 3-Trifluoromethylformanilide were reacted in a manner analogous to that described in Example 4 to give a first crop of 28.7 g. (93.5% of theory) of colourless crystals of N,Ndimethyl-N'-(3-trifluoromethylphenyl)-urea; m.p. 1 63-1 650C.

Example 8 N'-[4-(4-Chlorophenoxy)-phenyl]-N,N-dimethylurea 25 g. (0.1 mol) 4-(4-Chlorophenoxy)-formanilide were mixed with 30 g. dimethyl ammonium N,N-dimethyl thiolcarbamate salt and 250 ml. monochlorobenzene. The mixture was refluxed for 3.5 hours and then further worked up as described in Example 4 to give a first crop of 28 g. (96.5% of theory) of light coloured crystals of N'-[4-(4-chlorophenoxy)-phenyl]-N,N-dimethylurea; m.p. 151- 1530C.

Claims

1. Process for the preparation of substituted ureas of the general formula:

in which R is a hydrogen atom or an unsubstitued or substituted aliphatic, cycloaliphatic, aryl or heterocyclic radical and R1 and R2, which may be the same or different, are unsubstituted or substituted, straight-chained or branched aliphatic radicals, wherein a formyl compound of the general formula:

in which R has the same meaning as above, is reacted with a thiolcarbaNate salt of the general formula:

in which R1 and R2 have the same meanings as above.

2. Process according to claim 1, wherein the reaction is carried out in an inert solvent.

3. Process according to claim 2, wherein the solvent used is an aromatic, cycloaliphatic, heterocyclic or aliphatic solvent.

4. Process according to claim 3, wherein the solvent used is benzene, monochlorobenzene, dichlorobenzene, toluene, xylene, naphthalene or tetrahydrofuran.

5. Process according to any of the preceding claims, wherein the reaction is carried out at the reflux temperature of the reaction mixture.

6. Process according to any of the preceding claims, wherein the desired end product is obtained from the reaction mixture by stripping off volatiles.

7. Process according to claim 6, wherein the end product is purified by washing with and/or crystallising from an appropriate solvent.

8. Process according to claim 1 for the preparation of substituted ureas, substantially as hereinbefore described and exemplified.

9. Substituted ureas, whenever prepared by the process according to any of claims 1 to 8.