ANNULATION SEQUENCES EMPLOYING METHYL (E)-6-IODO-3-TRIMETHYLSTANNYL-2-HEXENOATES AND (Z)-6-IODO-3-TRIMETHYLSTANNYL-2-HEXENOATES AND RELATED BIFUNCTIONAL REAGENTS - PREPARATION OF CISOID CIS AND CISOID-TRANS BICYCLIC DIENES

A useful annulation method leading to the stereospecific synthesis of structurally novel, functionalized bicyclic dienes is described. Alkylation of 2-(methoxycarbonyl)cyclopentanone (34) and 2-(methoxycarbonyl)cyclohexanone (35) with methyl (E)- and (Z)-6-iodo-3-trimethylstannyl-2-hexenoates (27, 28) provided the keto diesters 36-39. Conversion of these substances into the corresponding enol triflates 47 50, followed by palladium(0)-catalyzed ring closure of the latter compounds, afforded the bicyclic dienes 55-58. In similar fashion, the keto esters 34 or 35 were transformed into the dienes 59-65. An X-ray crystallographic analysis of the p-nitrobenzoate 69, which was derived from the cisoid cis diene 64, showed that, in 69, the dihedral angle between the two carbon-carbon double bonds is -54.0(5)-degrees.