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Paper | Regular issue | Vol 78, No. 3, 2009, pp.717-724
Published online, 12th November, 2008
DOI: 10.3987/COM-08-11566
One Pot Synthesis of Optically Active 4-Isoxazolines by Asymmetric Addition of Alkynylzinc Reagents to Nitrones Followed by Cyclization

Weilin Wei, Masato Kobayashi, Yutaka Ukaji,* and Katsuhiko Inomata*

*Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan

Abstract

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.