Traceless Acetal-Directed Catalytic Hydrosilylation of Propargyl Acetates Harnessing the π-Acidic Catalyst

Traceless acetal-directed, α-specific syn-hydrosilylation of propargyl alcohols has been developed, enabling a synthesis of β-silyl allylic alcohols. An introduction of inexpensive, readily accessible acetal as a traceless, two-atom tether directing group (DG), along with a π-acidic catalyst, facilitates the proximal, α-selective syn-hydrosilylation of a broad spectrum of primary to tertiary propargyl alcohols. Notably, the utilization of a highly fluorinated, π-acidic Rh(I)/P(C₆F₅)₃ catalyst allows rapid cyclizing syn-addition of a silicon-metal species across a C-C triple bond via a strong M-π interaction. A postmodification of the resulting cyclic silyl acetal not only removes the DG, rendering it traceless, but also introduces a functional group to the silicon moiety, enhancing the versatility and utility of the products.