The cycloaddition reactions of thiomichler's ketone (1) with trans-1-substituted-1, 3-butadiene compounds [1-phenyl-1, 3-buta-diene(2a), 2, 4-methyl pentadienoate (2b), 1, 3-pentadiene (2c)] were studied. The reactions of 1 with 2a and 2b occurred at 50℃ and main cycloadducts (3a) and (3b) were formed. The reaction of 1 with 2c occurred at 70℃ to afford 91% cycloadduct (3c) and 9% isomer (4c). The structures of above adducts are supported by analytical and spectral data. The regioselectivity of 1 with 2a and 2c are con-sistent with the FMO theory. On the other hand, 2b in the reaction with 1 showed the regioselectivity to be different from the FMO theory prediction, affording 3b but not 4b. In this reaction, the steric hindrance may to be the major regiocontrolling factor.

Key words: CYCLOADDITION REACTION, FRONTIER ORBITAL THEORY, BUTADIENE P, STEREOCHEMISTRY, PENTADIENE, THIOKETONE