AM1 SEMIEMPIRICAL STUDY OF REACTIVITY OF BENZO[B]-THIOPHENE AND BENZO[C]-THIOPHENE AS DIENES IN DIELS-ALDER REACTIONS

We have undertaken an AM1 semiempirical study to examine the capability of benzothiophene to function as a diene in Diels-Alder reactions. Two approaches are considered: the evaluation of the aromaticity of dienes and corresponding transition-state structures, and the estimation of activation barriers. The aromaticity was determined from the heats of hydrogenation. The study was performed for the addition of ethene, tetracyanoethene and maleic anhydride to benzothiophenes. The theoretical data were in full agreement with the experimental data demonstrating the capability of these methods correctly to predict the reactivity of benzothiophenes, and the feasibility of their cycloaddition reactions.