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5699730 
Dissertation 
Part I. Reactions of alpha,beta-unsaturated thioesters and selenoesters with enamines. Part II. Alpha,beta-unsaturated thioesters and selenoesters as dienophiles: Synthesis of cyclohexene derivatives 
Byeon, CH 
1994 
Columbus, OH 
The Ohio State University 
Doctoral Dissertation 
English 
This thesis describes new aspects of the chemistry of $\alpha ,\beta$-unsaturated thioesters and $\alpha ,\beta$-unsaturated selenoesters. It was observed that these carboxylic acid derivatives show ketone-like reactivity in both conjugate addition and (4+2) -cycloaddition reactions. 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 $\beta$-substituted thioesters and selenoesters generally gave complementary stereochemical results in terms of relative stereochemistry at new stereogenic centers. In addition, the conformational preferences of a number of bicyclo(3.3.1) nonan-2,9-diones were determined using COSY and NOE nuclear magnetic resonance experiments. 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.