Thiol Additions To Dissymmetrical 1,4-Diary Sulfonyl-2-Butynes Regioselectivity And Stereoselectivity

Abstract
Regioselectivity is restored in the addition of thiols to 1,4-diarylsulfonyl-2-butynes based on differing electron-demands of the substituents on the aromatic rings attached to the butynyl sulfones. Kinetic control of addition leading to preponderant formation of the less stable vinyl sulfide with an E geometry is observed. Thermodynamic stability favors the Z isomer of the vinyl sulfide. The results are consistent with and confirm the rationale proposed earlier, implicating the intermediacy of an allene.