Catalytic Dicyanative [4+2] Cycloaddition Triggered by Cyanopalladation of Conjugated Enynes under Aerobic Conditions

A palladium-catalyzed dicyanative [4+2] cycloaddition reaction using dienynes with TMSCN under aerobic conditions is described. This new reaction triggered by the cyanopalladation of terminal alkynes includes regioselective direct cyanation to C-C triple bonds by TMSCN to give pi-allyl Pd intermediates, which promotes 5-exo followed by 6-endo cyclization. This protocol enables (1) the formation of four C-C bonds through one operation, (2) the construction of highly functionalized cyclohexene rings, and (3) the generation of five contiguous stereogenic centers in one operation. The intermolecular cycloaddition reaction between a conjugated enyne and methyl acrylate also proceeded in a regioselective fashion to give multifunctionalized carbocycles.