Photo- and Cu(I)-promoted branched-selective formal hydroacylation of terminal alkynes via the intermolecular coupling of siloxycarbenes with alkyne–Cu complexes

Abstract A photo-induced and copper-promoted coupling reaction of alkanoylsilanes and terminal acetylenes, which affords the corresponding α,β-enones in branched-selective manner, the formal hydroacylation products, has been developed. The established coupling is expected to proceed via the coupling of nucleophilic siloxycarbenes, which were generated by the light-induced isomerization of the corresponding alkanoylsilanes, with alkyne–copper π-complexes. This is the rare example of branched-selective hydroacylation of alkynes by utilizing the acyl sources other than aldehydes.