[3-ANNULATION AND [3+5]-ANNULATION REACTIONS OF ALPHA-(PHENYLTHIO) DICARBONYL ELECTROPHILES WITH BIS(TRIMETHYLSILYL) ENOL ETHERS - SYNTHESIS OF HIGHLY FUNCTIONALIZED MEDIUM RING CARBOCYCLES(4])

The [3 + 4] and [3 + 5] annulations of bis(trimethylsilyl) enol ethers with 1,4- and 1,5-dicarbonyl electrophiles bearing alpha-phenylthio s ubstituents leads to the formation of bicyclic [3.2.1] and [3.3.1] eth ers with good regiochemical and stereochemical control, Subsequent oxi dation of the phenylthio moiety followed by reduction with SmI2 consti tutes a high-yielding and regioselective process for cleavage of the b ridging ether linkage. The overall strategy provides a synthetic pathw ay for the synthesis of highly functionalized medium ring carbocycles.