Effects of ultrasound on the formation of α-benzoylbenzyl cyanide from benzyl cyanide and alkylphenyl ketone from α-alkylbenzyl cyanide by potassium superoxide in the presence of crown ether

Ultrasound accelerates the formation of α-benzoylbenzyl cyanide and benzoic acid in the reaction of benzyl cyanide with potassium superoxide in the presence of 18-crown-6. Similarly, 4-methylbenzyl cyanide, 4-methoxybenzyl cyanide and 4-chlorobenzyl cyanide gave the corresponding α-(4-methylbenzoyl)-4-methylbenzyl cyanide, α-(4-methoxybenzoyl)-4-methoxybenzyl cyanide and α-(4-chlorobenzoyl)-4-chlorobenzyl cyanide in 25–43% isolated yields under the same reaction conditions. Benzoic, p-toluic, 4-methoxybenzoic and 4-chlorobenzoic acids were also formed in these reactions. No reaction was observed when the mixture was simply stirred. Reflux instead of sonication gave lower yields of the products. However, α-alkylbenzyl cyanide produced a high yield of the phenylalkyl ketones when stirred. Interestingly, the corresponding benzoic acid was not formed in these reactions. Possible mechanisms for the formation of α-benzoylbenzyl cyanide from benzyl cyanide and phenylalkyl ketones from α-alkylbenzyl cyanide are also proposed.