| This thesis describes new aspects of the chemistry of ;Chapter 1 describes reactions of unsaturated thioesters and selenoesters with enamines of cycloalkanones. It was found that the pyrrolidine enamines of cyclohexanone and cycloheptanone provide moderate to good yields of bicyclo(3.3.1) nonan-2,9-diones and bicyclo(4.3.1) decan-2,10-diones, respectively. On the other hand, morpholine enamines provided only conjugate addition products. It was noted that ;Chapter 2 describes Diels-Alder reactions of thioesters and selenoesters derived from crotonic acid, fumaric acid, and methyl hydrogen fumarate with cyclopentadiene, isoprene, piperylene, and 2-trimethylsilyloxy-1,3-butadiene. Thermal reactions between these diene-dienophile pairs proceeded in good yield, but with poor control of stereochemistry and regiochemistry. Lewis acid promoted reactions, however, proceeded with excellent selectivity. In all cases, the thioesters and selenoesters played the role of the directing group. In addition, competition experiments showed that unsaturated thioesters and selenoesters derived from fumaric acid are 10-30 times more reactive with cyclopentadiene than their ester counterparts. Finally, cycloadducts obtained from the methyl hydrogen fumarate derivatives were subjected to selected transformations which established these dienophiles as reverse polarity acrylate equivalents. |
