One pot synthesis of optically active 4-isoxazolines by asymmetric addition of alkynylzinc reagents to nitrones followed by cyclization

摘要

One pot synthesis of optically active 4-isoxazolines was achieved by asymmetric addition of alkynylzinc reagents to nitrones utilizing di(t-butyl) (R,R)-tartrate as a chiral auxiliary followed by cyclization. By addition of dimethylzinc, the cyclization step was accelerated to afford the corresponding 4-isoxazolines with up to 93% ee. Furthermore, a cyclized zinc intermediate could be trapped with formaldehyde to give the corresponding 2,3,4,5-tetrasubstituted 4-isoxazoline with 85% ee. © 2009 The Japan Institute of Heterocyclic Chemistry All rights reserved.