The First General Method for the Synthesis of Transition-Metal π Complexes of an Electronically Diverse Family of 1,2-Azaborolyls

A general method for the synthesis of new families of transition-metal-free 1,2-azaborolides (3) has been developed, based on a readily available precursor (1). These azaborolides react with a variety of transition-metal electrophiles to produce an unprecedented array of η⁵-azaborolyl adducts (4) (substituents bound to boron:  nitrogen, oxygen, hydrogen, carbon, and phosphorus).