Temperature-Controlled Thiation of α‑Cyano-β-Alkynyl Carbonyl Derivatives for De Novo Synthesis of 2‑Aminothiophenes and Thieno[2,3‑<i>c</i>]isothiazoles

Making use of temperature-controlled thiation as a key operation, a simple route to 2-aminothiophenes or thieno­[2,3-<i>c</i>]­isothiazoles has been newly developed wherein the 2-aminothiophene nucleus was formed through an initial formation of thioamide followed by a 5-exo-dig addition to the tethered alkyne; however, under harsher thermal conditions, excess sulfur-transferring reagents enabled further oxidative thiation to generate the corresponding thieno­[2,3-<i>c</i>]­isothiazoles.