Asymmetric conjugate addition of arylboronic acids to enones mediated by rhodium/phosphoramidite complex

Asymmetric conjugate addition of arylboronic acids to enones mediated by rhodium/phosphoramidite complex Patrizia Scafato, Francesca Caprioli, Carlo Rosini Dipartimento di Chimica, Università degli Studi della Basilicata, via N. Sauro, 85; Potenza. francapri25@libero.it The asymmetric rhodium-catalyzed conjugate addition of aryl boronic acids nowadays is the method of choice for the stereoselective introduction of an aryl group in the β position of activated olefins.1 The catalytic efficiency of phosphoramidite L* has been tested on such a reaction with different enones, providing high yields and enantioselectivities (up to 96% e.e.) dependent on the nature of the carbonyl compound. Furthermore, preliminary investigations on the asymmetric addition of phenylboronic acid to chromones, substrates never utilized for this reaction, are reported. The results obtained indicate that also this reaction can occur with high enantioselectivity. Moreover, this synthetic approach could represent a new convenient access to chiral flavanones,2 an important class of natural and synthetic products which possess an impressive and varied array of biological and pharmacological properties. 1. (a) Fagnou, K.; Lautens, M. Chem. Rev. 2003, 103, 169-196; (b) Hayashi, T.; Yamasaki, K. Chem. Rev. 2003, 103, 2829-2844; (c) Christoffers, J.; Koripelly, G.; Rosiak, A.; Rössle, M. Synthesis 2007, 1279-1300. 2. Moorty, N. S. H. N.; Singh, R. J.; Sing, H. P.; Gupta, S. D. Chem. Pharm. Bull. 2006, 54, 1384-1390.