An efficient, generally applicable method for the synthesis of a varie
ty of 3,6-disubstituted 1,2-dithiins has been established. The method
involves the regio- and stereoselective 1,4-bis-addition of atkylthiol
s to 1,4-disubstituted 1,3-butadiyne at room temperature in DMF in the
presence of a catalytic amount of KOH. Subsequent reductive removal o
f the thiol-protecting group with Li/liq NH3/THF at -78-degrees-C foll
owed by oxidative ring closure of the resulting dilithium dithioenolat
es with I2/KI provides the red-colored 1,2-dithiins.