INTRAMOLECULAR PALLADIUM(0)-CATALYZED COUPLING OF ENOL TRIFLATE AND VINYLSTANNATE FUNCTIONS - NEW ANNULATION SEQUENCES LEADING TO BICYCLIC DIENE SYSTEMS

A new, concise annulation method leading to the efficient production of structurally novel bicyclic dienes has been developed. The individual synthetic steps that constitute this method, as outlined in general terms in Scheme 1, involve (a) the alkylation of (functionalized) carbonyl compounds with omega-iodo-2-trimethylstannyl-1-alkenes (17 --> 21), (b) the conversion of the alkylation products into the corresponding enol trifluoromethanesulfonates (triflates) (21 --> 22), and (c) the palladium(0)-catalyzed intramolecular coupling of the enol triflate-vinylstannanes to provide the dienes (22 --> 23). The generality of the method is demonstrated by the synthesis of functionalized bicyclo[4.3.0]nonane (61, 62, 65, 66), bicyclo[4.4.0]decane (63, 64, 67, 68, 71), bicyclo[5.3.0]decane (70), and bicyclo[5.4.0]undecane (69) derivatives.