Pyridine‐Based Organocatalysts for Regioselective syn‐1,2‐Silaboration of Terminal Alkynes and Allenes

AbstractAn organocatalytic silaboration of terminal alkynes and allenes was established using pyridine‐based catalysts. In the presence of 4‐cyanopyridine (1–2 mol%), alkyl propiolates underwent regio‐ and stereoselective addition of silylboronic esters in toluene at 135 °C to afford (Z)‐3‐boryl‐2‐silylacrylates in good yields. 2,6‐Dichloro‐4,4′‐bipyridine and 4‐(3,5‐dichlorophenyl)pyridine also exhibited high catalyst efficiency for the 1,2‐silaboration of ethyl propiolate, whereas 1,1‐silaboration was induced by P(n‐Bu)3, t‐BuOK, and ICy to afford ethyl 3‐boryl‐3‐silylacrylates as Z/E mixtures. The silaboration of ethynylbenzenes and terminal allenes was also catalyzed by 4‐cyanopyridine to afford (Z)‐β‐boryl‐α‐silylstyrenes and β‐borylallylsilanes in a regioselective manner.