PHOTOLYTIC DOUBLE DECARBONYLATION ROUTE TO HIGHLY SUBSTITUTED INDENESAND BENZENE-DERIVATIVES

UV irradiation of cyclohexane solution of a 4,7-ethanoindene-8,9-dione derivative led to a facile extrusion of two molecules of carbon monox ide to give a dihydroindene along with its dehydrogenated product, a m ethylene indene (benzofulvene). The inseparable mixture of dihydroinde ne and benzofulvene on treatment with DDQ underwent dehydrogenation an d equilibration to afford the latter as a single stereoisomer in high yield. The double CO extrusion process is a general reaction and it ha s been applied to the synthesis of a number of benzofulvenes and highl y substituted benzene derivatives.