Markovnikov Protoborylation of Unactivated Terminal Alkenes via Copper-Guanidine Catalysis

Abstract

Herein copper-catalyzed Markovnikov protoborylation of unactivated terminal alkenes was achieved through the employment of a bulky σ-donating guanidine ligand. The reaction demonstrated good tolerance to diverse functional groups and remarkable selectivity for branched borylation products (86:14–97:3) under ambient conditions, which enabled the synthesis of secondary alkyl boronates in grams with further valuable derivatizations. Mechanistic studies suggested the boryl insertion to C═C bonds via Cu-guanidine complex and ruled out the possibility of a diboration–protodeboronation process.