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

Traceless acetal-directed, <i>α</i>-specific <i>syn</i>-hydrosilylation of propargyl alcohols has been developed, enabling a synthesis of <i>β</i>-silyl allylic alcohols. An introduction of inexpensive, readily accessible acetal as a traceless, two-atom tether directing group (DG), along with a <i>π</i>-acidic catalyst, facilitates the proximal, <i>α</i>-selective <i>syn</i>-hydrosilylation of a broad spectrum of primary to tertiary propargyl alcohols. Notably, the utilization of a highly fluorinated, <i>π</i>-acidic Rh(I)/P(C₆F₅)₃ catalyst allows rapid cyclizing <i>syn</i>-addition of a silicon-metal species across a C-C triple bond via a strong M-<i>π</i> 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.