Overcoming Energy Transfer for the Metallophotoredox Catalyzed Decarboxylative Alkenylation between Alkylcarboxylic Acids and Enol Triflates.

Herein we report on the decarboxylative alkenylation between alkyl carboxylic acids and enol triflates. The reaction is mediated by a dual catalytic nickel and iridium system, operating under visible light irradiation. Two competing catalytic pathways, from the excited state iridium photocatalyst, are identified. One is energy transfer from the excited state, resulting in formation of an undesired enol ester. The desired pathway involves electron transfer, resulting in decarboxylation to ultimately give the target product. The use of a highly oxidizing iridium photocatalyst is essential to control the reactivity. A diverse array of enol triflates and alkyl carboxylic acids are investigated, providing both scope and limitations of the presented methodology.