3,4-Bis(trimethylsilyl)thiophene and several other 3,4-disubstituted thiophenes are synthesised by an unprecedented intermolecular cycloaddition窶田ycloreversion procedure between disubstituted acetylenes and 4-methyl- or 4-phenyl-thiazole; 3,4-bis(trimethylsilyl)thiophene undergoes consecutive regiospecific mono-ipso-iodination and palladium-catalysed reactions to provide unsymmetrically 3,4-disubstituted thiophenes.