A NOVEL ONE-FLASK CYCLOPENTANNULATION INVOLVING A DILITHIOMETHANE EQUIVALENT AS A BETA-CONNECTOR OF 2 ENONES - A HIGHLY EFFICIENT TOTAL SYNTHESIS OF (+ -)-HIRSUTENE/

Five- and six-membered rings can be constructed in one flask from two different enones and tris(phenylthio)methyllithium. The latter behaves as a dilithiomethane equivalent when its central carbon atom adds in conjugate fashion to one enone, becomes nucleophilic again when one of its phenylthio groups is exchanged for lithium in the presence of sec -butyllithium, and then undergoes conjugate addition to a second enone to provide a dienolate dainion. The latter can be oxidized to a 1,4-d iketone incorPorating a cyclopentane ring or induced to undergo an ald ol reaction to produce a six-membered ring. In some of the cases, an i nteresting stereochemical equilibration occurs during the oxidation le ading to One Of two possible diastreomers and the overall process resu lts in a highly efficient, stereospecific synthesis of (+/-)-hirsutene 13.