Internal Addition of Ketocarbenes to Conjugated Double Bonds

The internal, copper-catalysed, addition of keto-carbenes (generated from a diazoketone group) to a double bond conjugated either to a ketone or carboxylic ester function has been found to be a feasible preparative reaction in selected cases. This, together with the facile and regiospecific hydrogenolysis of the resulting 1,2-dicarbonyl cyclopropane intermediate, appear to constitute a convenient route to multifunctional bridged-ring systems.