131. Synthesis of 2-Cycloalkenones (Parts of 1,4-Diacyl-1,3-butadiene Systems) and of a Heterocyclic Analogue by Metal-Catalyzed Decomposition of 2-Diazoacylfurans

Article abstract of DOI:10.1002/hlca.19870700524

Furans with side-chains at C(2) of various lengths terminating in diazomethyl keto groups are shown to undergo Rh2(OAc)4-catalyzed furan unravelling with the production of 2-cyclopentenone, 2-cyclohexenone, and 2-cycloheptenone to each of whose olefinic C(β) is attached an acrylaldehyde unit.Interposition of a cyclohexane or a methylaminomethylene moiety between the furan and diazoketo functions leads to the formation of a hydroindenone and pyrrolone, respectively.Replacement of the diazomethylketo terminus by an α-diazoethylketo system or a α-diazo-β-keto-ester function produces 2-substituted 2-cycloalkenones.A furan with a C₄, diazomethylketo-terminating side-chain at C(3) is described to be transformed into a 4-formylmethylidene-2-cyclohexenone.