Regioselective Cross-Electrophile Propargyl–Silyl Coupling with Hydrochlorosilanes by Chromium Catalysis

The catalytic propargyl–silyl reductive coupling of propargyl electrophiles with silyl electrophiles represents an efficient approach to accessing propargylsilanes, which are versatile building blocks in synthetic and pharmaceutical chemistry. However, such a catalytic transformation has remained elusive and highly challenging. Herein, we report a regioselective cross-electrophile propargyl–silyl coupling of propargyl chlorides or esters with hydrochlorosilanes by chromium catalysis under mild conditions, providing an efficient and straightforward route for the synthesis of diverse propargyl hydrosilanes with broad substrate scope, good functional group compatibility, and high propargylic selectivity. Mechanistic studies suggest that the coupling reaction proceeds through a Cr(III)/Cr(II) cycle involving the generation of a propargyl radical via a single-electron transfer process, followed by the radical capture by a Cr(II) species to form a propargyl-Cr(III) species, and subsequent reduction by Mn and substitution with the Si–Cl bond in hydrochlorosilanes by the resulting propargyl-Cr(II) species.