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Intramolecular 1,3-Dipolar Cycloaddition of Nitrilimines Bearing Alkenyl Groups

1982; Oxford University Press; Volume: 55; Issue: 8 Linguagem: Inglês

10.1246/bcsj.55.2456

1348-0634

Tomio Shimizu, Y. Hayashi, Susumu Ishikawa, Kazuhiro Teramura,

Organic Chemistry Cycloaddition Reactions

The reaction of the arylhydrazones of some 2-(alkenyloxy)benzaldehydes(or 1-naphthaldehydes) with Pb(OAc)4 leads, via the nitrilimine intermediates, to intramolecular 1,3-dipolar cycloadducts, 3-substituted 2-aryl-2,3,3a,4-tetrahydro[1]benzopyrano(or naphtho[1′,2′:5,6]pyrano)[4,3-c]pyrazoles, in 10–80% yields. In the presence of an excess of Pb(OAc)4, these cycloadducts were dehydrogenated to 3-substituted 2-aryl-2,4-dihydro[1]benzopyrano(or naphtho[1′,2′:5,6]pyrano)[4,3-c]pyrazoles. In the presence of a large excess of Pb(OAc)4, some of the pyrazoles were acetoxylated to give the corresponding 4-acetoxypyrazoles. The effect of substituents of the alkenyl group on reactivity of the reaction was interpreted in terms of the frontier molecular orbital (FMO) theory.