Intra- and Intermolecular [3++2] Cycloadditions of Aldehyde or Ketohydrazones

Abstract

Abstract The reaction of several 2-(alkenyloxy)benzaldehydes (or 1-naphthaldehydes) (1) with arylhydrazine hydrochlorides leads to intramolecular [3++2] cycloadducts, 3-substituted 2-aryl-1,2,3,3a,4,9b(or 1,2,3,3a,4,11c)hexahydro[1]benzopyrano (or naphtho[1′,2′:5,6]pyrano)[4,3-c]pyrazole hydrochlorides (4), in good yields. Free bases (5) were obtained in high yields after the treatment of 4 with triethylamine. The thermal treatment of 5 at 150 °C gave 3-substituted 2-aryl-2,3,3a,4-tetrahydro[1]benzopyrano(or naphtho[1′,2′:5,6]pyrano)[4,3-c]pyrazoles. The reaction of 1 with methylhydrazine sulfate gave the corresponding 2-methyl derivatives. Analogous intramolecular [3++2] cycloadducts were obtained from the reaction of 2′-(alkenyloxy)acetophenones with arylhydrazine hydrochlorides. Intermolecular [3++2] cycloadducts were also obtained from a reaction mixture of 1-naphthaldehyde, arylhydrazine hydrochlorides, and styrene.