Isoxazolines by cycloadditions of mesitonitrile oxide with benzo[b]thiophene S-oxide and S,S-dioxide. Structural studies, theoretical explanations, and kinetics
regioselective cycloaddition to benzonitrile oxide. In the reaction with the less reactive mesitonitrile oxide the sulfur dioxide deriving from the dimerization of the dipolarophile causes a catalytic decomposition of the nitrileoxide, which competes with the cycloaddition. Benzothiophene-1,1-dioxide and the vinyl sulfone system of 2,3-dihydrothiophene-1,1-dioxide and nitrileoxides with lower regioselectivity