AN IMPROVED PROCESS FOR PREPARING 3,4-DIHYDROQUINOXALINE-2(1H)ONES

摘要

An approved process for preparing 3, 4-dihydroquinoxaline-2(H) ones, of Formula ''A'' shown in Fig. 1of the accompanying drawing wherein R3, R5, R6, R7 and R8 stand for hydrogen in 3, 4-dihydroquinoxaline-2(1H) one and in substituted ones where R3, R5, R6, R7 and R8 stand for hydrogen unless otherwise specified as methyl eithyl, phenyl, chlorine, bromine and carboxylic acid group; from o-phenylene diamine represented by Formula ''C'' of Fig. 3or its substitutes containing the R5, R6, R7 and R8 having the same meaning as hereinabove defined, the said process comprising reacting the said o-phenylene diamine with a solution of alpha-halo said such as monochloro acetic acid partly neutralized to pH to 6 and heating the said reaction mixture at temperature ranging from 40 to 90 degree Celsius preferably at 70 degree Celsius during a period ranging from 2 to 9 hours characterized in that the said reaction is carried out in the presence of a catalyst such as the acetate salt of a heavy metal like barium or lead and the reaction being further allowed to continue for a period ranging from 2 to 4 hours after which the product is separated by neutralization of the reaction mixture with soda ash to pH 7 and by salting out by addition of sodium sulphate to obtain desired product of Formula ''A'' as shown in Fig. 1 of the accompanying drawing.