Electron donor–acceptor complex formation between malononitrile‐like substrate and α‐keto carboxylic acids happens via a hydrogen bond which facilitates hydroacylation reaction without any exogenous photocatalyst. A variety of substituted benzylidene malononitrile and α,β‐unsaturated ketones were efficiently hydroacylated utilizing α‐keto acids as both the acyl and hydrogen atom source. The transformation proceeds smoothly under mild reaction conditions, with carbon dioxide being the sole byproduct. Mechanistically, the reaction is driven by a charge transfer transition that generates the acyl radical upon decarboxylation of α‐keto carboxylic acid, driving the reaction via a radical pathway.
Singh et al. (Fri,) studied this question.