TRIALKYLBORANE AS AN INITIATOR AND TERMINATOR OF FREE-RADICAL REACTIONS - FACILE ROUTES TO BORON ENOLATES VIA ALPHA-CARBONYL RADICALS AND ALDOL REACTION OF BORON ENOLATES

A variety of trialkylborane-induced reactions were examined for the preparation of the alpha-carbonyl radicals: (1) addition of alkyl radical to methyl vinyl ketone, (2) reduction of alpha-halo ketone, and (3) intramolecular radical addition to alpha, beta-unsaturated carbonyl moiety. Trialkylborane reacted with alpha-carbonyl radicals to give boron enolates. The resulting boron enolates were efficiently trapped by carbonyl compounds to give beta-hydroxy ketones in good yields.