Highly Selective β‐Hydride Elimination in the Pd‐Catalyzed Cross‐Coupling of N‐Tosylhydrazones with Benzyl Bromides

Abstract

AbstractIn Pd‐catalyzed cross‐coupling reactions between tosylhydrazones and organohalides, the competitive β–H elimination of palladium complex intermediate generated through palladium‐carbene complex's migratory insertion is usually avoided by combining two specific coupling partners, in which only one contains a β‐H. To address this limitation, herein we present cross‐coupling reactions between benzyl bromides and tosylhydrazones derived from benzocyclic ketones. Benzyl‐substituted dihydronaphthalenes and 1H‐indenes can be obtained in up to 88% yields and 25:1 selectivity for the cyclic olefin via this method. DFT studies were performed to elucidate the reaction mechanism. The β‐H elimination process, which follows the migratory insertion of Pd carbene intermediates, favours the abstraction of hydrogen atoms on the cyclic skeletons and results in the observed regioselectivity.