Photo-catalyzed dearomative coupling of benzylmalonates and alkynes with CO2 leading to spiro-1,4-cyclohexadiene carboxylic acids

A dearomative coupling reaction of benzylmalonates and alkynes with CO 2 via visible-light catalysis is developed, leading to a series of spiro-1,4-cyclohexadiene carboxylic acids. This three-component transformation achieves sequential dearomatization, alkenylation, and carboxylation of non-activated benzene ring, building spiro architecture and installing two functional groups in one reaction step. The strategy has the advantages of mild conditions, broad substrate scope, low loading of photocatalyst, redox neutral, excellent yield and high selectivity. Gram-scale reaction and product derivatizations indicate promising application prospects. Mechanistic studies reveal that the reaction might proceed through tandem radical addition, dearomatization and nucleophilic addition. A dearomative coupling of benzylmalonates and alkynes with CO 2 via visible-light catalysis is achieved, leading to various spiro-1,4-cyclohexadiene carboxylic acids. A broad scope of substrates could realize this three-component reaction with the advantages of green conditions, low loading of photocatalyst, redox neutral, excellent yield and high selectivity.