Catalytic decomposition of branched α'-phenoxy-α-iazo ketones affording 2, 8h-cyclohepta[b]furan-3-one and 2h-cyclohepta[b]furan-3a(3ah)methyl-3-one

Abstract

The decomposition induced by bis(hexafluoroacetoacetonato)Cu II on branched α-diazo ketones 1 bearing a phenoxy group at the α'-carbon has been investigated. The course of the reactions has been shown to be dependent upon substitution. Mixtures of furanones 2 and chromanones 4 were obtained from α-unsubstituted substrates 1b– d, as in the case of 1a. Instead, among the α-mono substituted substrates 1f and 1g selectively gave cycloneptatrienes 3f and 3g, respectively, while 1e and 1h gave mixtures of the corresponding 3 and 4. Cycloheptatrienes 3 easily rearranged to chromanones 4. The intermediacy of norcaradienes 5 has been tentatively proposed in the catalytic decomposition of 1, and in rearrangement of 3e– h to 4e– h.