Access to 2-Amino-3-Arylthiophenes by Base-Catalyzed Redox Condensation Reaction Between Arylacetonitriles, Chalcones, and Elemental Sulfur

摘要

A straightforward access to 2-amino-3-arylthiophenes has been developed via one-pot two-step three-component reaction of arylacetonitriles, chalcones and elemental sulfur. The first step consists of a DBU-catalyzed formation of Michael adduct between arylacetonitriles and chalcones. The second step is a cascade of DABCO-catalyzed sulfuration of the Michael adduct with elemental sulfur followed by an oxidative cyclization to afford thiophenes. Compared to the Gewald reactions and related transformations which are limited in acetonitriles bearing a methylene group activated by an alpha-substituted electron withdrawing group as substrates, our method can be applied to a wide range of arylacetonitriles and requires only catalytic amounts of DBU and DABCO. The developed reaction opens an access to 3-aryl-2-aminothiophenes complementary to classical Gewald reactions with high degree of structural diversity and atom efficiency.