trans-Silaboration of Terminal Alkynes Enabled by Development of a New Si─B Reagent

The 1,2-silaboration of alkynes is a powerful strategy for regio- and stereoselective yielding versatile 1-boryl-2-silyl alkenes, which are ubiquitous synthons leveraging the orthogonal reactivity of boron and silicon for diverse downstream transformations. However, it dominantly features cis-selectivity. trans-Selective silaboration remains underdeveloped to date, especially for sterically hindered terminal alkynes. Herein, we report a Pd-catalyzed trans-silaboration of terminal alkynes using a novel Si─B reagent, TBSQ, bearing an 8-quinolinyl directing group on silicon. This strategy provides exclusive E-selectivity across a broad substrate scope, including bulky alkynes. Mechanistic studies suggest a combined cis-addition/Z→E isomerization pathway, with the directing group playing a crucial role. The resulting trans-1-boryl-2-silyl alkenes serve as valuable building blocks for selective downstream functionalization toward pharmaceutically relevant molecules.