Metal-Free Reagent Dependent SS and CC Homocoupling of α-Enolic Dithioesters at Room Temperature: Direct Access to Fully Substituted Symmetrical Thiophenes via Chemoselective Paal-Knorr Approach

Abstract

An unprecedented metal-free oxidative homodimerization of α-enolic dithioesters has been achieved for the first time at room temperature within 5–10 min. Molecular iodine promotes the SS coupling leading to S,S′-bis(dithioacetals), while N-chlorosuccinimide facilitates CC coupling to give α,α′-bis(β-oxo dithioesters) in good to excellent yields. Furthermore, the newly generated α,α′-bis(β-oxo dithioesters) have been directly employed in the synthesis of fully substituted thiophenes with a unique symmetrical substitution pattern in a one-pot, two-step reaction sequence.