Photocatalytic carbyne reactivity of phosphorus ylides for three-component formal cycloaddition reactions

Selective reactions between more than two molecules are governed by appropriate combinations of polar functionalities. This restriction can be ameliorated by photoredox umpolung reactivity, which enables the functionalization of unreactive bonds of chemical reagents while leaving their inherent reactive functional groups intact, paving the way for otherwise difficult multicomponent reactions. Here we report that the photocatalytic single-electron oxidation of phosphorus ylides underpins their sequential assembly with electron-rich olefins and α,β-unsaturated carbonyl compounds to form functionalized six-membered carbocycles. This three-component formal cycloaddition, featuring consecutive C–H functionalization and Wittig reaction of phosphorus ylides, offers a carbyne-like transformation that involves the conversion of inert C–H and C=P bonds into C–C and C=C bonds, respectively, as a powerful tool for the rapid construction of versatile synthetic building blocks from readily available substrates.