GB1583756A

GB1583756A - Process for the preparation of nitriles and nitriles obtaining thereby

Info

Publication number: GB1583756A
Application number: GB3396976A
Authority: GB
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 1976-08-16
Filing date: 1976-08-16
Publication date: 1981-02-04
Also published as: JPS5323947A; NL7708901A

Description

(54) PROCESS FOR THE PREPARATION OF NITRILES AND NEW NITRILES OBTAINABLE THEREBY (71) We, SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V., a company organised under the laws of The Netherlands, of 30 Carel van Bylandtlaan, The Hague, The Netherlands, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement:- The invention relates to a process for the preparation of 2-aryl substituted alkenenitriles and to novel nitriles obtainable thereby.

Bull. Soc. Chim. France 1963, pp. 677681 shows that 3-methyl-2-phenyl-2butenenitrile can be prepared in 30% yield by refluxing 0.3 mol of benzyl cyanide, 1.3 mol of acetone and 10 ml 3N methanolic KOH for two hours, followed by cooling, neutralizing, drying and distilling. This publication also shows that 2phenyl-2-butenenitrile is obtained in 47% yield by heating 0.25 mol of benzyl cyanide, 1 mol of acetaldehyde and 2 ml 3N methanolic KOH until the mixture becomes cloudy (about 65"C), followed by cooling, neutralizing, drying and distilling. The applicant has found that further stirring under reflux does not increase these low yields. The molar ratios of KOH to benzyl cyanide in these two experiments were 0.10:1 and 0.024:1, respectively.

It has now been found that an increase of the molar ratio of alkali metal hydroxide to the cyanide reactant considerably enhances the said yields.

Accordingly the invention provides a process for the preparation of a nitrile of the general formula

wherein R' represents an optionally-substituted aryl group, R2 a substituted or unsubstituted hydrocarbyl group and R3 a substituted or unsubstituted hydrocarbyl group and R3 a substituted or unsubstituted hydrocarbyl group or a hydrogen atom, or, alternatively, R2 and R3 together with the carbon atom to which they are attached form a carbocyclic group, which comprises reacting a nitrile of the general formula R1-CH2CN, (11) wherein RX has the same meaning as in the general formula I, with a carbonyl compound of the general formula

wherein R2 and R3 have the same meaning as in the general formula I, in the presence of an alkanol and a hydroxide of an alkali metal having an atomic number of at least 11, using a molar ratio of the hydroxide to the compound of the general formula II of at least 0.15:1.

The molar ratio of the alkali metal hydroxide to the compound of the general formula II must be at least 0.15:1 to ensure an enhanced yield of the compounds of the general formula 1. This molar ratio is preferably in the range of from 0.2 to 0.8:1 molar ratios increasing above 0.1:1 usually offer no additional advantages.

Preferred molar ratios are usually in the range of from 0.3 to 0.6:1.

R1 in the general formula II may be a carbocyclic or a heterocyclic aryl group.

Examples of carbocyclic aryl groups are phenyl, I-naphthyl, 2-naphthyl and 2anthryl groups. Heterocyclic aromatic groups are derived from hetero-aromatic compounds which are defined as in Kirk-Othmer, "Encyclopedia of Chemical Technology", Second Edition, Volume 2 (1963), page 702: obtained by replacement of one or more carbon atoms of a carbocyclic aromatic compound by a heteroatom for example pyridine, pyrimidine, pyrazine, quinoline and isoquinoline -- and these heteroaromatic compounds also include those heterocyclic compounds having five-membered rings which show aromatic characteristics and are mentioned on page 703 of said volume, for example thiophene, pyrrole, furan, indole and benzothiophene. Examples of substituents which may be present in R1 are alkyl or alkoxy groups or halogen atoms. Very high yields of compounds of the general formula I are usually obtained when R1 represents a substituted or unsubstituted phenyl group, particularly a 4-chlorophenyl group.

Preferred alkanols are those having less than ten carbon atoms per molecule.

The alkanol may have a straight or a branched carbon chain. Methanol, ethanol, 1propanol, 2-propanol and the butanols are particularly preferred. Methanol is the most preferred of these alcohols, because it usually affords the compounds of the general formula I in the highest yield after the same reaction time.

Among the alkali metal hydroxides - i.e. the hydroxides of sodium, potassium, rubidium and caesium -- potassium hydroxide is preferred, because it usually affords the compounds of the general formula I in a higher yield than sodium hydroxide after the same reaction time and because it is less expensive than the hydroxides of rubidium and caesium. If desired, the alkali metal hydroxide may be formed in situ, for example by starting from the corresponding alkali metal oxide.

The hydrocarbyl groups represented by R2 and R3 in the general formula III may be, for example, an alkyl, a cycloalkyl or an aryl group or one of these which is substituted by another one of these three groups. If desired the hydrocarbyl groups may be substituted by non-hydrocarbyl groups, for example by an alkoxy group.

The alkyl and cycloalkyl groups may be saturated or unsaturated. Very good results have been obtained with compounds in which R2 and R3 stand for alkyl groups.

Examples of ketones of the general formula III which may be used are acetone, 2butanone, 2-pentanone, 4-methyl-3-pentene-2-one, acetophenone and 1'butyronaphthone. Acetone is particularly preferred. Examples of aldehydes of the general formula III are propanal, butanal and hexanal. Examples of compounds of the general formula III wherein R2 and R3 together with the carbon atom to which they are attached form a carbocyclic group are cyclobutanone, cyclopentanone, cyclohexanone and cyclododecanone. The carbocyclic group may contain unsaturated carbon-carbon bonds, as is the case in, for example, 2-cyclohexene-lone and methyl derivatives thereof.

The compounds of the general formulas III and II are preferably used in a molar ratio of III to II of at least 1:1 low yields of nitriles of the general formula I are obtained at molar ratios below 1:1. This molar ratio is preferably in the range of from 1.5 to 10:1 and particularly of from 2 to 5:1.

The molar ratio of alkanol to alkali metal hydroxide can vary between wide limits and is usually between I and 20:1.

The compounds of the general formula I are usually obtained in a low yield after a long time - at temperatures below 50"C; temperatures in the range of from 50 to 100"C are usually very suitable. Temperatures higher than 100"C may be used, if desired.

The process may be conducted in the presence of a solid water-binding agent, for example of calcium oxide, sodium carbonate or potassium carbonate.

The process may be carried out by stirring a mixture of the nitrile of the general formula II, the carbonyl compound of the general formula III and the alkanol and adding the alkali metal hydroxide to the stirred mixture. Then, the mixture is heated for a certain time. The nitrile of the general formula I may be isolated from the reaction mixture thus obtained by flashing off carbonyl compound of the general formula III, dissolving the organic material of the residue in an organic solvent such as petroleum ether or toluene, removing alkali metal hydroxide by washing with water until the used washing water has a pH of 7, drying the washed solution and subjecting the dried solution to fractional distiliation.

Nitriles of the general formula I may be converted into the corresponding amides by replacing the cyano group by a carbamoyl group in a known manner.

The carboxamides thus obtained may be converted in a known manner into the corresponding carboxylic acids.

Compounds of the general formula I are valuable intermediates, particularly for the preparation of pesticides, such as esters of 2-(4-chlorophenyl)-3-methylbutanoic acid, which are valuable insecticides.

The Examples further illustrate the invention.

EXAMPLE I.

Preparation of 2-(4-chlorophenyl)-3-methyl-2-butenenitrile A flask was charged with 0.2 mol of 4-chlorobenzyl cyanide, 0.57 mol (42 ml) of acetone, 0.27 mol (11 ml) of methanol and 0.09 mol of potassium hydroxide in pellets containing 15%w of water, the molar ratios of KOH to 4-chlorobenzyl cyanide and of acetone to 4-chlorobenzyl cyanide being 0.45:1 and 2.85:1, respectively. The contents of the flask was stirred and boiled for ten minutes under reflux at atmospheric pressure. Then, acetone and methanol were flashed off, the organic material in the residue was dissolved in 60 ml of toluene and potassium hydroxide was removed by washing the solution with two 20-ml portions of water.

The washed solution was dried over anhydrous magnesium sulphate, the magnesium sulphate was removed by filtration and the toluene was flashed off, leaving a yellow orange liquid residue (41.8 g) containing 2-(4-chlorophenyl)-3methyl-2-butenenitrile in an amount corresponding to yield of more than 95%, calculated on starting 4-chlorobenzyl cyanide. The conversion of 4-chlorobenzyl cyanide was 100%.

EXAMPLE II.

Preparation of 2.(4-chlorophenyl)-3-methyl-2-butenenitrile The experiment of Example I was repeated, but this time 0.15 mol of NaOH in pellets was used instead of 0.09 mol of KOH pellets, the molar ratio of NaOH to 4chlorobenzyl cyanide being 0.75:1. 2-(4-Chlorophenyl)-3-methyl-2-butenenitrile was formed in a yield of more than 9.5% after a reaction time of 32 minutes.

EXAMPLE III.

Preparation of 2-(4-chlorophenyl)-3-methyl-2-butenenitrile The experiment of Example I was repeated, but this time 0.285 mol instead of 0.57 mol of acetone was used, the molar ratio of acetone to 4-chlorobenzyl cyanide being 1.425:1, and the contents of the flask were stirred for fifteen instead of ten minutes. The conversion of 4-chlorobenzyl cyanide was 100% and the yield of 2-(4chlorophenyl)-3-methyl-2-butenenitrile was 80%, calculated on starting 4chlorobenzyl cyanide.

EXAMPLE IV.

Preparation of 2-(4-chlorophenyl)-3-methyl-2-butenenitrile The experiment of Example I was repeated, but this time 0.045 mol instead of 0.09 mol of potassium hydroxide was used, the molar ratio of KOH to 4-chlorobenzyl cyanide being 0.225:1, and the contents of the flask was stirred for 55 instead of 10 minutes, It was found that 70% of the 4-chlorobenzyl cyanide had been converted, mainly to 2-(4-chlorophenyl)-3-methyl-2-butenenitrile. Further stirring did not increase the conversion.

EXAMPLE V.

Preparation of 2-(4-chlorophenyl)-3-methyl-2-butenenitrile The experiment of Example I was repeated, but this time 11 ml of 2-propanol instead of 11 ml of methanol was used and the contents of the flask were stirred under reflux for 30 instead of 10 minutes. The conversion of 4-chlorobenzyl cyanide was 100% and the yield of 2-(4-chlorophenyl)-3-methyl-2-butene nitrile was more than 95%, calculated on starting 4-chlorobenzyl cyanide.

EXAMPLES VI-XII.

A flask was charged with 5 g of an arylacetonitrile, 10 ml of a carbonyl compound, 2 ml of methanol and 1 g of KOH pellets. Seven experiments were conducted as described in Example I. The arylacetonitriles and carbonyl compounds used and the reaction times adopted are stated in the Table. The Table also presents the names of the nitriles formed and their yields, calculated on starting arylacetonitrile. The nitriles formed in the Examples IX, X, XI and XII are novel.

TABLE Molar ratio of Nitrile formed Reaction Example KOH to aryl- Carbonyl compound time, Yield, No. Arylacetonitrile Carbonyl compound acetonitrile to arylacetonitrile min. Name % VI benzyl cyanide acetone 0,35:1 3,2:1 15 3-methyl-/2-phenyl- 80 2-butenenitrile VIII ditto 2-butanone 0,35:1 2,6:1 38 3-methyl-2-phenyl-2- 100 pentenenitrile VIII ditto n-butanal 0,35:1 2,6:1 10 2-phenyl-2-hexene- 100 nitrile IX p-chlorobenzyl 4-methyl-3-pentene- 0,35:1 2,0:1 8 2-(4-chlorophenyl)-3,5- 30 cyanide tene-2-one dimethyl-2,4-hexadiene nitrile X 1-naphthyl cyanide acetone 0,51:1 4,5:1 20 3-methyl-2-(1-naphthyl)- 70 2-butenenitrile XI 4-methylbenzyl ditto 0,40:1 3,6:1 22 3-methyl-/2-(4-methyl- 80 cyanide phenyl)-2-butenenitrile XIII 3,5-dimethyl- ditto 0,45:1 4,0:1 20 2-(3,5-dimethylphenyl)- 60 benzyl cyanide 3-methyl-2-butenenitrile The nuclear magnetic resonance spectrum of the novel nitrile formed in Example IX measured at 60 MHz in deuterochloroform solution showed the following absorptions relative to a tetramethylsilane standard: # = 1.73 ppm (singlet, two CH3); # = 1.82 ppm (doublet, one CH3); # = 6.03 ppm (multiplet, = CH); # = 7.30 ppm (singlet, four H bound to aromatic nucleus). The E and Z structures were both present.

Analysis of the residues obtained in the Examples X, XI and XII by means of infrared spectrography yielded the following absorptions (wave length in micron): Example X: 4.56; 12.47; 12.87.

Example XI: 4.56; 12.20; 12.25.

Example XII: 4.55; 11.77; 14.25.

EXAMPLE XIII.

The experiment of Example VI was repeated, but this time I g of sodium hydroxide was used instead of 1 g of KOH pellets, the molar ratio of NaOH to benzyl cyanide being 0.58:1. 3-Methyl-2-phenyl-2-butenenitrile was formed in a yield of 60% after a reaction time of 17 minutes.

EXAMPLE XIV.

A flask was charged with 0.033 mol of 4-chlorobenzyl cyanide, 0.057 mol of cyclobutanone, 0.05 mol (2 ml) of methanol and 0.015 mol of KOH in pellets containing 15 / w of water, the molar ratios of KOH to 4-chlorobenzyl cyanide and of cyclobutanone to 4-chlorobenzyl cyanide being 0.45:1 and 1.73:1, respectively.

The contents of the flask were stirred and boiled for five minutes under reflux at atmospheric pressure. The reaction mixture was taken up in diethyl ether, the etherial solution was washed with water until the washing water had a pH of 7, the washed solution was dried in the presence of anhydrous magnesium sulphate and the dried solution was boiled down at subatmospheric pressure. The residue (6.25 g) showed the following infrared absorptions (in micron), indicating the presence of the novel compound 2-(4-chlorophenyl)-2-cyclobutylideneethanenitrile: 3.0; 3.40; 3.47; 3.54; 4.50; 4.56; 5.30; 5.70; 6.10; 6.30; 6.75; 6.96; 7.14; 8.0; 9.20; 9.90; 11.10; 11.42; 11.66; 12.10; 12.58; 13.70; 14.34.

EXAMPLE XV.

The experiment of Example XIV was repeated, but this time 0.057 mol of 3,55trimethyl-2-cyclohexen-1-one was used instead of cyclobutanone. The residue contained the novel compound 2-(4-chlorophenyl)-2-(3,5,5-trimethyl-2 cyclohexen- l-ylidene)ethanenitrile.

The NMR spectrum of this novel compound measured at 60 MHz in deuterochloroform solution showed the following absorptions relative to a tetramethylsilane standard (the E and Z structures were both present): S = 0.86 and 1.02 ppm (two singlets, geminal CH3); a = 1.81 and 1.93 ppm (two singlets, one CH3 bound to =C); = 2.04-2.08-2.23-2.52 ppm (CH2 ring protons); a = 6.18 and 6.63 ppm (two singlets, =C); 7.31 ppm (singlet, four H bound to aromatic nucleus).

Claims

WHAT WE CLAIM IS:

1. Process for the preparation of a nitrile of the general formula

wherein R' represents an optionally-substituted aryl group, R2 a substituted or unsubstituted hydrocarbyl group and R3 a substituted or unsubstituted hydrocarbyl group or a hydrogen atom or, alternatively, R2 and R3 together with the carbon atom to which they are attached form a carbocyclic group which comprises reacting a nitrile of the general formula R1-CH2CN , (11) wherein R' has the same meaning as in the general formula I, with a carbonyl compound of the general formula

2. Process as claimed in claim 1, in which the group R' in the general formula II represents a substituted or unsubstituted phenyl group.

3. Process as claimed in claim 2, in which the nitrile of the general formula II is 4-chlorobenzyl cyanide.

4. Process as claimed in any one of the preceding claims, in which the alkanol has less than ten carbon atoms per molecule.

5. Process as claimed in claim 4, in which the alkanol is methanol.

6. Process as claimed in any one of the preceding claims, in which the alkali metal hydroxide is potassium hydroxide.

7. Process as claimed in any one of the preceding claims, in which the molar ratio of the alkali metal hydroxide to the nitrile of the general formula II is in the range of from 0.2 to 0.8:1.

8. Process as claimed in claim 7, in which the molar ratio of the hydroxide to the nitrile of the general formula II is in the range of from 0.3 to 0.6:1.

9. Process as claimed in any one of the preceding claims, in which R2 and R3 are aliphatic groups.

10. Process as claimed in claim 9, in which R2 and R3 are alkyl groups.

II. Process as claimed in claim 10, in which R2 and R3 are methyl groups.

12. Process as claimed in any one of the preceding claims, in which the compounds of the general formulas III and II are used in a molar ratio of III to II of at least 1:1.

13. Process as claimed in claim 12, in which the molar ratio of III to II is in the range of from 1.5 to 10:1.

14. Process as claimed in any one of the preceding claims, which is conducted at a temperature in the range of from 50"C to 1000C.

15. Process as claimed in claim 1, substantially as hereinbefore described, with reference to the Examples I to XV.

16. Nitriles of the general formula I stated in claim 1, whenever prepared by a process as claimed in any one of the preceding claims.

17. 3-Methyl-2-( 1 -naphthyl)-2-butenenitrile.

18. 3-Methyl-2-(4-methylphenyl)-2-butenenitrile.

19. 2-(3,5-Dimethylphenyl)-3-methyl-2-butenenitrile.

20. 2-(4-Chlorophenyl)-2-cyclobutylideneethanenitrile.

21. 2 - (4 - Chlorophenyl) - 2 - (3,5,5 - trimethyl - 2 - cyclohexen - 1 - ylidene)- ethanenitrile.

22. 2-(4-Chlorophenyl)-3,5-dimethyl-2,4-hexadienenitrile.