Synthesis of 2-(Alkyl(or aryl)sulfanyl)benzo[b]thiophen-3-amines by LDA-mediated Cyclization of 2-{[(Alkyl(or aryl)sulfanyl)methyl]sulfanyl}benzonitriles

A new and convenient method for the preparation of 2-(alkyl(or aryl)sulfanyl)benzo[b]thiophen-3-amines has been developed.Thus, 2-{[(alkyl(or aryl)sulfanyl)methyl]sulfanyl}benzonitriles, prepared by successive treatment of 2-halobenzonitriles with anhydrous disodium sulfide and chloromethyl sulfides, are cyclized to the desired products via lithiation of the carbon between two sulfur atoms with LDA, followed by addition of the resulting carbanion to the nitrile carbon.New and efficient methods for the general preparation of benzo[b]thiophenes have been being developed 1,2 due to importance of these derivatives in heterocyclic chemistry.However, there have been no general methods for the preparation of 2-(alkyl(or aryl)sulfanyl)benzo[b]thiophen-3-amines of potential biological interest so far, though the synthesis of 2-(ethylsulfanyl)-and