Cyclization of Homopropargyl Chalcogenides by Copper(II) Salts: Selective Synthesis of 2,3‐Dihydroselenophenes, 3‐Arylselenophenes, and 3‐Haloselenophenes/thiophenes

Abstract

Copper(II) halide mediated cyclization of homopropargyl chalcogenides gave three types of chalcogenophene derivatives. Selective product formation was achieved by controlling solvent, temperature, and atmosphere. By using CuBr2 and 1,2-dichloroethane at room temperature under ambient atmosphere, 4-bromo dihydroselenophene derivatives were obtained, whereas CuBr2 and 1,2-dichloroethane at reflux gave selectively 2-substituted selenophenes. When 1,2-dichloroethane was replaced by dimethylacetamide, 3-halo-selenophenes were obtained exclusively. The versatility of chalcogenophenes was also studied by reaction of 3-haloselenophenes with terminal alkynes under Sonogashira conditions affording the cross-coupled products. In addition, the reaction of 3-haloselenophenes with boronic acids gave the corresponding Suzuki-type products in good yields.