Phase-Transfer-Catalyzed, Enantioselective Vinylogous Conjugate Addition–Cyclization of Olefinic Azlactones To Access Multifunctionalized Chiral Cyclohexenones

An asymmetric, phase-transfer-catalyzed vinylogous conjugate addition–vinylogous cyclization cascade of olefinic azlactones with 4-nitro-5-styrylisoxazoles is reported. In the presence of an l-tert-leucine-derived urea–quaternary ammonium salt as a bifunctional phase-transfer catalyst and KF, two series of valuable optically pure cyclohexenones featuring two and three stereocenters were obtained in high yields with good to excellent enantio- and diastereoselectivities