Novel synthesis of substituted thiophenes by palladium-catalyzed cycloisomerization of (Z)-2-en-4-yne-1-thiols

[reaction: see text] The first example of palladium-catalyzed cycloisomerization of (Z)-2-en-4-yne-1-thiols 1 to give substituted thiophenes 2 is reported. Cycloisomerization reactions are carried out under nitrogen at 25-100 degrees C in N,N-dimethylacetamide as the solvent in the presence of catalytic amounts of PdI2 in conjunction with KI to give the corresponding thiophenes in 43-94% yield.