Synthesis of 3-Amino-4-iodothiophenes through Iodocyclization of 1-(1,3-Dithian-2-yl)propargylamines

1-(1,3-Dithian-2-yl)propargylamines undergo iodo-cylization regioselectively to afford tetrasubstituted 3-amino-4-iodothiophenes in 30-87 % yields by iodide induced cleavage of dithiane ring in a bicyclic sulfonium intermediate. A mechanism for this unprecedented transformation was proposed and tentatively supported by the isolation of an intermediate structure. 1-(1,3-Dithian-2-yl)propargylamines were prepared in 30-94 % yields by Au-catalyzed one-pot, three-component reaction of 1,3-dithiane-2-carbaldehydes, amines, and alkynes so called A(3)-coupling reaction.