Synlett 2010(4): 628-632  
DOI: 10.1055/s-0029-1219365
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

New Regiospecific Catalytic Approaches to 4,5-Dihydroisoxazoles and 2,5-Dihydroisoxazoles from O-Propargylic Hydroxylamines

David W. Knight*a, Anthony J. Proctora, John M. Cloughb
a School of Chemistry, Cardiff University, Main College, Park Place, Cardiff, CF10 3AT, UK
Fax: +44(2920)874030; e-Mail: knightdw@cf.ac.uk;
b Syngenta, Research Chemistry, Jealott’s Hill International Research Centre, Bracknell, Berkshire, RG42 6EY, UK
Further Information

Publication History

Received 9 November 2009
Publication Date:
02 February 2010 (online)

Abstract

Unprotected O-propargylic hydroxylamines undergo generally essentially quantitative cyclisations when exposed briefly to silver nitrate adsorbed onto silica gel to give 4,5-dihydroisoxazoles [2-isoxazolines], while N-protected derivatives give the corresponding 2,5-dihydroisoxazoles [3-isoxazolines] in similarly excellent yields, given that an appropriate functionality on nitrogen is used.

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Hatherley J. L., Knight D. W. unpublished observations.