<i>trans</i> ‐Silaboration of Terminal Alkynes Enabled by Development of a New Si─B Reagent

Abstract 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.