Ligandless Copper-Catalyzed β-Boration of α,β-Unsaturated Compounds in Aqueous Solution

Abstract

This protocol, however, showed limit-ed substrate scope as reactions went to completion only with simple substrates having no substituents at the α and β posi-tions. Efficient catalysis without specific coordinating ligands on the metal catalysts would be desirable. Herein, we report a ligandless protocol for the copper-catalyzed β-boration of α, - unsaturated carbonyl compounds in aqueous THF solution. The use of water as a co-solvent and a reaction promoter exerted a positive effect on catalytic efficiency and resulted in the efficient β-boration of α,β-unsaturated carbonyl compounds including substituted enones and esters. This new, operationally simple method is useful for the preparation of racemic organoboron compounds.Our investigation of the boration reaction under ligand-free conditions began with β-monosubstituted enones using 5 mol % CuCl, 5 mol % NaO