Enolboration. 3. An examination of the effect of variable steric requirements of R on the stereoselective enolboration of ketones with R2BCl/Et3N. Bis(bicyclo[2.2.2]octyl)chloroborane/triethylamine, a new reagent which achieves the selective generation of E enolborinates from representative ketones

Abstract

Abstract : A smooth, rapid, quantitative and stereoselective enolboration of a variety of ketones to E enolborinates is achieved with bis(bicyclo2.2.2octyl) chloroborane, Bco2BC1, a new reagent, in the presence of triethylamine, in simple solvents, such as diethyl ether, hexane, carbon tetrachloride, and methylene chloride. Representative R2BC1 reagents with variable steric requirements have been examined, with 3-pentanone and propiophenone as model ketones, in order to understand the effect of the steric requirements of R in controlling the enolate geometry.