Rhodium-catalyzed enantioselective 1,4-additions of arylboronic acids to substituted enones

The rhodium-catalyzed enantioselective 1,4-addition of arylboronic acids to the bifunctional Michael acceptors 1-3 in the presence of phosphoramidites L2-L4 occurs regioselectively at the endocyclic C-C double bond and in up to 95% ee. The presence of KOH is required to increase the reactivity so that less boronic acid and lower reaction temperatures can be used. The corresponding addition to chiral enone 4 takes place with epimerization of the product to the thermodynamically more stable trans-isomer, which was obtained with up to 98% ee. (c) 2006 Elsevier Ltd. All rights reserved.