Tris(trimethylsilyl)silylboronate Esters: Novel Bulky, Air- and Moisture-Stable Silylboronate Ester Reagents for Boryl Substitution and Silaboration Reactions

Abstract

New, bulky tris(trimethylsilyl)silylboronate pinacol and hexylene glycol esters ((TMS)3Si–B(pin) and (TMS)3Si–B(hg)) were prepared in 46 and 61% yields, respectively, by the reaction of tris(trimethylsilyl)silylpotassium with the corresponding boron electrophiles. Notably, these silylboronate esters exhibited high stability to air and silica gel and were applied to the transition-metal-free boryl substitution of aryl halides, providing the desired borylated products in high yields with excellent B:Si ratios (up to 96% yield, B/Si = 99/1). These new silylboronate esters were also applied to a sequential borylation/cross-coupling process with various aryl halides, as well as the base-mediated silaboration of styrene.