SU899553A1 - Process for preparing 2-methyl-3-ethoxycarbonylquinoxalines - Google Patents

Description

The invention relates to a new method for producing 2-methyl ~ 3-ethoxycarbonylquinoxaline formulas

where R = NiliS !, which can be used as intermediate ¹⁰ products in the synthesis of biologically active compounds.

A known method of producing 2-methyl ~ 3 ^_ ethoxycarbonylquinoxalin, which consists in the fact that ethyl ester * ⁵ acetyldiazoacetic acid is reacted with phenylsulfene chloride, the resulting 2-chloro-2-phenylmercapto-3-oxo-butyric acid in the presence of o-phenylenediamine in the presence of 1}

The disadvantage of this method is the complexity of the process technology, which consists in carrying out the process in two stages.

Closest to the invention in technical essence and the achieved Effect is a method for producing 2-methyl-3-ethoxycarbonylquinoxaline, which consists in the fact that O-phenylenediamine is reacted with * ώ-chloroacetoacetate ether in the presence of calcium carbonate for 8 hours. The yield of the target product 10 % [2].

The disadvantage of this method is the low yield of the target product.

The aim of the invention is to increase the yield of the target product.

This goal is achieved by the production method, which consists in the fact that intramolecular cyclization of ethyl ester of 2-chloro-3 “(0-amino-p-Z-anilino) -crotonic acid in xylene or dimethylformamide in the presence of triethylamine at the boiling point of the reaction mixture and the target product is isolated in 60% yield.

Found,%: C 57.7; H 4.8;

SS 11.8.

^C -fd ^H

Calculated,% ·. C 57.5; H 4.8; C & 11.2.

Using the proposed method for producing 2-methyl-3 ~ ethoxycarbonylquinoxalin compared with known methods eliminates the use of hard-to-reach, unstable and toxic starting reagents, the method provides an increase in the yield of the target product (60%) by 50% and reduces the reaction time by 25%.

The advantage of the proposed method is the use of ethyl esters

2-chloro-3 (o-amino-p-R-anilino) -crotonic acid, conducting the reaction under milder conditions, reducing the reaction time from 8 to 6 hours

Example 1. Obtaining 2-methyl-3-ethoxycarbonylquinoxaline.

1.3 g (0.005 mol) of ethyl gz of 2-chloro-3 ~ (0 ~ aminoanilino) -crotonic acid ester in 10 ml of xylene • or dimethylformamide are boiled in the presence of

3.4 ml (0.025 mol) of triethylamine for 6 hours. The precipitate of triethylamine hydrochloride formed is filtered off, the solvent is distilled off in vacuo. The residue is crystallized from water. 0.62 g (57%) of 2-methyl-3-ethoxycarbonylquinoxaline, mp. 72-73 ° C.

Example 2. Obtaining 2-methyl-3 ~ ethoxycarbonyl-6-chloroquinoxaline.

A mixture of 1.44 g (0.005 mol) of 2-chloro-3 (2-amino-4-chlororanilino) -crotonic acid ethyl ester ЗЛ ml (0.025 mol) of triethylamine in 10 ml of xylene or dimethylformamide is boiled for 6 hours. After separation of the precipitate triethylamine hydrochloride and distillation of the solvent, the residue is crystallized from a mixture of alcohol (1: 1). Obtained 0.78 g (62%), so pl. 86 ° C.

Claims (1)

Claim A method of obtaining 2-methyl-3-ethoxycarbonylquinoxaline general formula I where R = H or C1 ₍ characterized in that, in order to increase the yield of the target product, carry out intramolecular cyclization of ethyl ether 2-chloro-3- (0-amino-nR-anilino ) -crotonic acid in xylene or dimethylformamide in the presence of triethylamine at the boiling point of the reaction mixture and the desired product is isolated.