Synthesis of 2,3-dihydroisoxazoles from propargylic N-hydroxylamines via Zn(II)-catalyzed ring-closure reaction

[GRAPHICS] A novel cyclization reaction of propargylic N-hydroxylamines to 2,3,5-trisu bstituted 2,3-dihydroisoxazoles in the presence of catalytic amounts (10 mo l %) of Znl(2) and DMAP is reported. The methodology provides a mild new ap proach to this useful class of substituted heterocycles that complements ex tant methods. The unique reactivity of the propargylic N-hydroxylamine subs trates in the presence of Zn(II) and DMAP may have additional applications in other, related alkyne cyclization reactions.