Rhodium-Catalyzed Asymmetric Access to P-Chiral Triarylphosphine Oxides via Insertion of P─H Bonds into Diazonaphthoquinones

Abstract

While significant progress has been made in the enantioselective insertion of carbenes into heteroatom-hydrogen bonds, this chemistry is restricted to the construction of carbon-based chirality. The asymmetric insertion of carbenes into P─H that delivers P-chiral products remains untouched. Rhodium(I)-catalyzed enantioselective synthesis of P-chiral triarylphosphine oxides via asymmetric C─P coupling of a secondary phosphine oxide (SPO) with diazonaphthoquinone is herein reported. Driven by aromatization, this protocol affords a variety of P-chiral triarylphosphine oxides tethered to a 2-naphthol functionality in excellent enantioselectivity by following a kinetic resolution reaction pattern. The diverse synthetic and catalytic applications of the P-chiral products highlight the value of this method, even though the derivatized trivalent chiral phosphine bears a rather low barrier of racemization.

Keywords: Asymmetric P─H Insertion; Carbene; Chiral phosphine oxides; P‐chirality; Rhodium.