OXIDATION AND REDUCTION REACTIONS OF HIGHLY FUNCTIONALIZED ALLYL STANNANES - BICYCLIC AND TRICYCLIC ALPHA-STANNYLMETHYL ENONES PREPARED VIATHE ROBINSON ANNULATION REACTION OF BETA'-STANNYLETHYL VINYL KETONE

5-(Tributylstannyl)-1-penten-3-one is prepared in 50% overall yield fr om the readily available 3-((triethylsilyl)-oxy)-1,4-pentadiene. Use o f this reagent in the Robinson annulation reaction provides alpha-stan nylmethyl enones in very good yields. Cerium-mediated 1,2 reduction fo llowed by acylation affords the corresponding allylic acetate. Both cl asses of compounds undergo specific S(E)2' oxidation with lead tetraac etate, mCPBA, and halogenating agents at the tertiary center of the al lylic stannane to initially afford exocyclic olefins. Rearrangement of the allylic acetates and allylic halides subsequently provides the is omeric endocyclic enone bearing a functionalized methyl group. Further chemistry includes Birch reduction of an alpha-stannylmethyl enone to a saturated alpha-stannylmethyl ketone as well as application of the Robinson annulation strategy to a hydrophenanthrene system. Attempts t o effect additional Robinson annulation reactions on substrates alread y bearing the tributylstannane moiety either fail or proceed in very p oor yield.