Regio- and Stereo-Chemistry of Addition of Molecular Bromine to S-Oxidized Derivatives of 3,4-Di-t-butylthiophene: Exclusive 1,4-Cis-Additions

Bromine added to the 1-oxide, 1,1-dioxide, and sulfoximide derivatives of 3,4-di-t-butylthiophene exclusively in a 1,4-cis-addition mode. Thus, bromine added to 3,4-di-t-butylthiophene 1-oxide at room temperature in CH2Cl2 to give the 1,4-cis-adducts exclusively. The adducts are composed of two compounds in the ratio 57 : 43, where the major one is the anti-adduct respective to the S=O bond and the minor one is the syn-adduct. Addition of bromine to 3,4-di-t-butylthiophene 1,1dioxide gave the 1,4-cis-adduct as the sole product. Addition of bromine to the N-tosyl substituted sulfoximide derivative of 3,4-di-t-butylthiophene afforded the single 1,4-cis-adduct in which two bromine atoms are anti to the N-tosyl group. Bromine added to the N-unsubstituted sulfoximide derivative of 3,4-di-tbutylthiophene to produce the 1,4-cis-addition products exclusively, which are a 67 : 33 mixture of the anti- and syn-adducts to the S=O bond.