GB2070584A

GB2070584A - Process for Producing N-alkyl- N-acyl-2,6-dialkylanilines

Info

Publication number: GB2070584A
Application number: GB7942414A
Authority: GB
Original assignee: Ciba Geigy AG
Current assignee: Novartis AG
Priority date: 1979-12-08
Filing date: 1979-12-08
Publication date: 1981-09-09

Abstract

An improved process for producing N-alkyl-N-acyl-2,6- dialkylanilines of the formula <IMAGE> wherein R1 and R2 independently of one another are methyl or ethyl, R3 is 1-methoxycarbonylethyl, 2- methoxyethyl, 2-ethoxyethyl, 2-n- propoxyethyl or 1-methyl-2- methoxyethyl, and R4 is chloromethyl, methoxymethyl or 2-furyl, by reaction of a N-alkyl-2,6-dialkylaniline of the formula <IMAGE> wherein R4 and R2 have the meanings given above, with an acid chloride of the formula R4-CO-Cl wherein R4 has the meaning given above, which process comprises adding the N-alkyl-2,6-dialkylaniline at 20 to 80 DEG C to a solution of the acid chloride in an inert solvent; subsequently evacuating the reaction vessel, in the same temperature range, to a pressure of 300 to 100 Torr; and after addition of water, layer- separation and removal of the organic solvent by evaporation, obtaining the N-alkyl-N-acyl-2,6-dialkylaniline of the above formula in the form of a melt.

Description

SPECIFICATION Process for Producing N-Alkyl-N-Acyl-2,6dialkylanilines The present invention relates to an improved process for producing N-alkyl-N-acyl-2,6dialkylanilines of the formula

in which R1 and R2 independently of one another are methyl or ethyl, R3 is 1 -methoxycarbonylethyl, 2-methoxyethyl, 2-ethoxyethyl, 2-n-propoxyethyl or 1 methyl-2-methoxyethyl, and R4 is chloromethyl, methoxymethyl or 2-furyl, by reaction of an N-alkyl-2,6-dialkylaniline of the formula II

in which R1, R2 and R3 have the meanings given under the formula I, with an acid chloride of the formula Ill R4-CO-Cl (Ill), in which R4 has the meaning given under the formula I, in an inert solvent.

The N-alkyl-N-acyl-2,6-dialkylanilines of the formula I, particularly N-(2'-methoxyethyl)-Nchloroacetyl-2,6-dimethylaniline, N-(1 '- methoxycarbonylethyl)-N-chloroacetyl-2-methyl6-ethylaniline, N-(2'-n-propoxyethyl)-Nchloroacetyl-2,6-diethylaniline, N-(1 ' methoxycarbonylethyl)-N-furoyl-2,6- dimethylaniline and N-(1 '-methoxycarbonylethyl) N-methoxyacetyl-2,6-dimethylaniline, have an excellent fungicidal action against phytopathogenic fungi, and can therefore be used for the protection of plants from damage caused by fungus infestation. N-alkyl-N-acyl-2,6dialkylanilines of the formula I are described for example in the German Offenlegungsschriften 2,305,495, 2,328,340,2,513,788 and 2,515,091.

The manner of producing N-alkyl-N-acyl-2,6dialkylanilines of the formula I by reaction of the corresponding n-alkyl-2,6-dialkylanilines with an acid chloride is known. The reaction is performed both in the absence and in the presence of inorganic or organic bases, such as sodium hydroxide, sodium carbonate and N,Ndimethylaniline. When however the reaction is performed in the presence of inorganic bases, a large excess of carboxylic acid chloride is required since a considerable part of the acid chloride is lost as a result of hydrolysis. On the one hand this is uneconomical, and on the other hand it causes ecological problems because the acid formed by hydrolysis has to be removed from the waste water.The disadvantage of using a large excess of acid chloride can of course be avoided by the use of organic bases, but in this case the amine hydrochloride formed in each case has to be recovered from the aqueous phase, which constitutes an additional expenditure.

Compared with the aforementioned process, the process comprising the direct reaction of an N-alkyl-2,6-dialkylaniline of the formula II with an acid chloride of the formula Ill in an inert solvent in the absence of a base does have the advantage that the hydrogen chloride formed in the reaction can be immediately separated in the gaseous form. In order however to effect the complete separation of the hydrogen chloride it is necessary to heat the reaction mixture for several hours at temperatures of 90 to 1 1 OOC, a procedure which leads to the formation of resinous by-products, and which reduces the yield of active substance.

By virtue of their inherent disadvatages, the processes mentioned in the foregoing are not suitable for an economical production of N-alkyl N-acyl-2,6-dialkylanilines of the formula I. It is therefore the object of the present invention to provide a process by which the N-alkyl-N-acyl2,6-dialkylanilines of the formula I can be produced on a commercial scale without great expenditure and in good yields.

The process according to the invention for producing N-alkyl-N-acyl-2,6-dimethylanilines of the formula I comprises adding the N-alkyl-2,6dialkylaniline of the formula II at 20 to 800C to a solution of the acid chloride of the formula III in an inert solvent: subsequently evacuating the reaction vessel, in the same temperature range, to a pressure of 300 to 100 Torr; and, after the addition of water, layer-separation and removal of the organic solvent by evaporation, obtaining the formed N-alkyl-N-acyl-2,6-dialkylaniline of the formula tin the form of a melt.

The process according to the invention is performed in particular at temperatures of 40 to 600 C. Suitable inert solvents are aliphatic and aromatic hydrocarbons, and also halogenated, aliphatic and aromatic hydrocarbons such as benzene, toluene, hexane, cyclohexane, chlorobenzene, dichlorobenzene, methylene chloride, chloroform and carbon tetrachloride. A particularly suitable solvent is toluene.

The addition of the N-alkyl-2,6-dialkylanilines of the formula II to the solution of the acid chloride of the formula III in one of the aforementioned inert solvents is made according to the invention in the course of half to 1-1/2 hours. After completion of the addition of the Nalky-2,6-dialkylaniline of the formula 11, the reaction vessel is slowly evacuated to 300 to 100 Torr. This operation requires as a rule 1.5 to 3 hours.

Before processing of the reaction mixture, this is firstly washed once or twice with water. The pH value of the reaction mixture is at the same time advantageously adjusted to 7 to 8 by the addition of aqueous sodium hydroxide solution. After separation of the aqueous phase, the formed N alkyl-N-acyl-2,6-dialkylaniline of the formula I is obtained by removal of the solvent by evaporation. This operation is advantageously performed firstly in a water-jet vacuum and subsequently under high vacuum at temperatures of 70 to 1000C. The yield of N-alkyl-N-acyl-2,6 dialkylaniline of the formula I is practically quantitative. The product is obtained in excellent purity, and can be used directly without further purification.

It is possible by means of the process according to the invention to produce the N-alkyl N-acyl-2,6-dialkylanilines of the formula I without losses in yield and with a low manufacturing costs. It is surprising that, in spite of the relatively - low reaction temperatures, at which still no thermal splitting-off of the aniline hydrochloride occurs, it is possible to effect a complete reaction in a relatively short period of time.

The process according to the invention is further illustrated by the following Example.

Example Production of N-(1 '-methoxycarbonylethyl)-Nmethoxyacetyl-2,6-dimethylaniline A solution of 119 g (1.1 mols) of methoxyacetyl chloride in 600 g of toluene is firstly placed into a reaction flask provided with stirrer, thermometer and condenser, and 207 g (1.0 mol) of N-(1 '-methoxycarbonylethyl)-2,6dimethylaniline is subsequently added at 45 to 500C in the course of 1 hour. After completion of the addition, the reaction vessel is evacuated at 45 to 500C firstly to 300 to 400 Torr, and subsequently during 1 to 2 hours continuously down to 80 to 120 Torr. The reaction mixture is afterwards cooled to 20 to 250C, and 400 ml of water is added. After separation of the aqueous phase, and addition of a further 400 ml of water, the pH of the reaction mixture is adjusted, with stirring, to 8 by the addition of 30% sodium hydroxide solution. The aqueous phase is separated, and the organic phase is freed from solvent firstly in a water-jet vacuum and subsequently under high vacuum at a temperature of about 900C. The yield is 279 g of N-( 1 '-methoxycarbonylethyl)-N-methoxyacetyl- 2,6-dimethylaniline (100% of theory).

Claims

1. A process for producing N-alkyl-N-acyl-2,6diaikylanilines of the formula I

in which R1 and R2 independently of one another are methyl or ethyl R3 is 1 -methoxycarbonylethyl, 2-methoxyethyl, 2-ethoxyethyl, 2-n-propoxyethyl or 1 methyl-2-methoxyethyl, and R4 is chioromethyl, methoxymethyl or 2-furyl, by reaction of an N-alkyl-2,6-dialkylaniline of the formula II

in which Ra, R2 and R3 have the meanings given under the formula I, with an acid chloride of the formula III R4-C0-Cl (III), in which R4 has the meaning given under the formula I, in an invert solvent, which process comprises adding the N-alkyl-2,6-dialkylaniline of the formula II at 20 to 800C to a solution of the acid chloride of the formula Ill in an inert solvent; subsequently evacuating the reaction vessel, in the same temperature range, to a pressure of 300 to 100 Torr; and, after the addition of water, layer-separation and removal of the organic solvent by evaporation, obtaining the formed N alkyl-N-acyl-2,6-dialkylanilines of the formula I in the form of a melt.

2. A process according to Claim 1, wherein the addition of the N-alkyl-2,6-dialkylaniline of the formula II to the solution of the acid chloride of the formula Ill in an inert solvent and the subsequent vacuum treatment are performed at 40 to 600C.

3. A process according to Claim 1 or 2, wherein the inert solvent used is a solvent from the group comprising: aliphatic hydrocarbons, aromatic hydrocarbons, halogenated aliphatic hydrocarbons and halogenated aromatic hydrocarbons.

4. A process according to Claim 3, wherein the inert solvent used is a solvent from the group comprising; benzene, toluene, hexane, cyclohexane, chlorobenzene, dichlorobenzene, methylene chloride, chloroform and carbon tetrachloride.

5. A process according to Claim 4, wherein the inert solvent is toluene.

6. A process according to any preceding claim, wherin the addition of the N-alkyl-2,6dialkylaniline of the formula II to the solution of the acid chloride of the formula Ill in an inert solvent is performed in the course of half to one and a half hours.

7. A process according to any preceding claim, wherein the evacuation of the reaction vessel to a pressure of 300 to 100 Torr is performed during one and a half to three hours.

8. A process according to Claim 1, substantially as hereinbefore described, with reference to the foregoing Example.