Combination of 1,2‐hydroboration and 1,1‐organoboration: synthesis of novel organo‐substituted 1‐silacyclobutenes

Abstract

AbstractThe reaction of di(alkyn‐1‐yl)silanes Me(R)Si(CCtBu)2 [1; R = Me (a), H (b)] with diethylborane or 9‐borabicyclo[3.3.1]nonane in a 1 : 1 ratio affords the 1‐silacyclobutene derivatives 6a, 7a,b as a result of intermolecular 1,1‐hydroboration followed by intramolecular 1,1‐organoboration. Intermediates, in which both an alkenyl and an alkynyl group are linked to silicon (2a, 3a), were identified and prepared independently by the reaction of the corresponding chlorosilane 5a with the lithium alkynide LiCCtBu. This procedure also opened the way to a stepwise synthesis of 1‐silacyclobutenes with a choice of substituents in the 2,4‐positions (6b and 9a). All reactions were monitored by 29Si NMR spectroscopy, and the structural assignment of the final products was based on multinuclear magnetic resonance data (1H, 11B, 13C and 29Si NMR). Copyright © 2003 John Wiley & Sons, Ltd.