Copper-catalyzed tandem S-alkylation and S-alkenylation of sodium sulfide: synthesis of 2,3-dihydrothiophenes and thiophenes

An efficient synthetic approach to variously substituted 2,3-dihydrothiophenes has been developed. The reaction proceeded by copper-catalyzed tandem S-alkylation and S-alkenylation of sodium sulfide with 1,4-diiodobut-1-enes to afford the corresponding 2,3-dihydrothiophene derivatives in high yields. The 2,3-dihydrothiophenes could bear alkyl, aryl as well as heteroaryl substituents. The resulted 2,3-dihydrothiophenes could be further transferred into the corresponding thiophenes by oxidation.