Switch of Addition and Ring-Opening Reactions of Oxabicyclic Alkenes with Terminal Alkynes by sp2-C,P- and sp3-C,P-Palladacycle Catalysis

Abstract

Palladacycles were found to be efficient catalysts for the reaction of oxabicyclic alkenes with terminal alkynes. A switch of reaction selectivity was realized using a palladacycle with an sp2 or sp3 C–Pd bond. Addition products were afforded predominantly using a palladacycle with an sp3 C–Pd bond, while ring-opening compounds were the major products when palladacycles having an sp2 C–Pd bond were used. DFT calculations revealed that the different trans effects of the sp2-C and sp3-C donors in palladacycles are responsible for the switch in selectivity.