Reactivity of (3-chloro-2-methylenecycloalkyl)pallladium Chloride Dimers: A Palladium Mediated Ring Homologation--Functionalization Approach to the AR-7-7 Skeleton of Colchicine
A palladium mediated ring homologation--functionalization approach to the Ar-7-7 tricyclic skeleton of colchicine from 1-arylcyclohexenes is described. This methodology involves the chloropalladation of 1-aryl-7-methylenebicyclo[4.1.0]heptanes to afford aryl substituted (3-chloro-2-methylenecycloheptyl)palladium chloride dimers. Reaction of the π-allyl complexes with one equivalent of malonate anion gives a cycloheptadiene product. Subsequent reduction and intramolecular acylation yields the Ar-7-7 skeleton.