Traceless Acetal-Directed Catalytic Hydrosilylation\nof Propargyl Acetates Harnessing the π‑Acidic Catalyst

Traceless acetal-directed, α-specific <i>syn</i>-hydrosilylation of propargyl alcohols has been developed,\nenabling\na synthesis of β-silyl allylic alcohols. An introduction of\ninexpensive, readily accessible acetal as a traceless, two-atom tether\ndirecting group (DG), along with a π-acidic catalyst, facilitates\nthe proximal, α-selective <i>syn</i>-hydrosilylation\nof a broad spectrum of primary to tertiary propargyl alcohols. Notably,\nthe utilization of a highly fluorinated, π-acidic Rh(I)/P(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> catalyst allows rapid cyclizing <i>syn</i>-addition of a silicon–metal species across a\nC–C triple bond via a strong M-π interaction. A postmodification\nof the resulting cyclic silyl acetal not only removes the DG, rendering\nit traceless, but also introduces a functional group to the silicon\nmoiety, enhancing the versatility and utility of the products.