A General Synthesis of B-(cis-1-Bromo-1-alkenyl)dialkylboranes. Valuable Intermediates for the Synthesis of Ketones, Trans Alkenes, and Trisubstituted Alkenes

Abstract

Dialkylboranes, generated in situ via hydridation of dialkylhaloboranes, hydroborate 1-bromo-1-alkynes to provide cleanly B-(cis-1-bromo-1-alkenyl)dialkylboranes. Treatment of these intermediates with sodium methoxide results in the migration of one of the alkyl groups on boron to the adjacent carbon, displacing the bromine, providing B-(trans-1-alkyl-1-alkenyl)alkylborinate esters. These intermediates provide ketones on oxidation, stereospecific trans alkenes on protonolysis, and trisubstituted alkenes on iodination, all in high yields. © 1982, American Chemical Society. All rights reserved.