Abstract
Following the preceding work on the action of hydrogen peroxide on α-cyano-ketones, a total of 20 kinds of α-cyano esters and α-cyanamides were synthesized and their reactivity with hydrogen peroxide in dilute alkali hydroxide solution was examined. The compounds synthesized included six kinds of ethyl arylcyanoacetates (I), six kinds of 2-aryl-2-cyanoacetamides (II), four kinds of ethyl 2-cyano-3-aryl-propionates (III), and four kinds of 2-cyano-3-arylpropionamides (IV), which are structurally related to α-cyanoketones. (I) and (II), which are similar to α-cyano-ketones in that they dissolve rapidly in the dilute alkali hydroxide solution, also formed the corresponding arylcarboxylic acids in 60-95% yield by decomposition with hydrogen peroxide and the manner of their decomposition was found to be the same as that of α-cyanoketones. On the other hand, (III) and (IV) are sparingly soluble in the alkaline reaction solution and their decomposition seemed to proceed in a different manner from that of α-cyanoketones. With one exception of (III), which formed arylacetic acid derivatives, all formed only a few per cent of aryl-carboxylic acid.
The mechanism of this decomposition reaction by hydrogen peroxide was examined from the foregoing experimental evidences. It was thereby assumed that the compounds of (I) and (II) types, in which the effect of aryl and cyano groups work additively to form enolic C=C bond between the α-carbon and CO, undergo oxidative cleavage at this portion to form arylcarboxylic acid, while in the compounds of (III) and (IV) types, in which aryl and cyano groups do not work additively and there is no formation of the enolic bond, a double bond character between the methylene and α-carbon conjugated to the aryl group is increased to a certain extent and oxidative decomposition of this bond results in the formation of arylcarboxylic acid.
The present series of experiments have given some evidences on the effect of cyano and aryl groups on enolization of a carbonyl in esters and amides with small carbonyl activity.
