Photochemical carboborylation and three-component difunctionalization of α,β-unsaturated ketones with boronic acids via tosylhydrazones.

The reactions of cyclic α,β-unsaturated N-tosylhydrazones and alkylboronic acids promoted by 370-390 nm light in the presence of a base give rise to allylic boronic acids that can be trapped as the corresponding pinacolboronates by treatment with pinacol. This reaction features wide scope regarding both coupling partners and functional group tolerance, allowing for the incorporation of a variety of natural product-derived fragments. The allylic boronic acids can be also reacted in a one-pot process with aldehydes, to produce homoallylic alcohols with very high diastereoselectivity. A three-component one-pot procedure has been developed revealing that the methodology is a powerful tool for the generation of structural diversity that is accomplished by incorporation of an ample variety of each of the three elements. Moreover, from a synthetic perspective, in the reaction, the formation of two C-C bonds, at the carbonyl and the β positions of a α,β-unsaturated carbonyl, has been achieved in the three-component reaction.