THE PALLADIUM-CATALYSED VINYLIC SUBSTITUTION OF VINYL TRIFLATES WITH BETA-SUBSTITUTED-ALPHA,BETA-UNSATURATED CARBONYL COMPOUNDS - AN APPLICATION TO THE SYNTHESIS OF CARDENOLIDES

摘要

Vinyl triflates react with beta-substituted-alpha,beta-unsatuated aldehydes, ketones, and esters in the presence of catalytic amounts of Pd(OAc)(2) and an excess of KOAc, omitting phosphine ligands, to give vinylic substitution products in good to high yield with high regioselectivity. The added vinyl unit is preferentially linked to the beta-carbon atom. As to the stereochemistry, vinylic substitution products contain the carbonyl group on the same side of the preexisting beta-substituent. The use of it KOAc has been proved to be superior both to tertiary amines and to carbonate or biacarbonate bases with or without the addition of salts such as LiCl and n-Bu(4)NCl. The application, or. the reaction, to the synthesis of a cardenolide derivative is reported. Depending on the nature of beta-substituted-alpha,beta-unsaturated carbonyl compounds, the reaction can produce hydrovinylation (formal conjugated addition) products. Copyright (C) 1996 Elsevier Science Ltd [References: 36]