Air- and Water-Tolerant (PNP)Ir Precatalyst for the Dehydrogenative Borylation of Terminal Alkynes

Abstract

This work discloses the facile synthesis and efficacy of (PNP)IrH(OAc), a precatalyst for the dehydrogenative borylation of terminal alkynes (DHBTA). Unlike the previously reported precatalysts in the (PNP)Ir system (PNP = diarylamido/bis(phosphine) pincer), it is air-stable in the solid state. Upon exposure to air in solution, it possesses a useful half-life on the order of 1–100 h, depending on the intensity of mixing. Air-degraded solutions of (PNP)IrH(OAc) retain DHBTA catalytic activity and selectivity upon exposure to the mixture of a terminal alkyne and HBpin. It is also demonstrated that (PNP)Ir-catalyzed DHBTA is compatible with the presence of modest amounts of moisture or air and that the catalyst is sufficiently long-lived to deliver turnover numbers (TONs) of > 100 000.