Thiol–Yne Coupling of Propargylamine under Solvent‐Free Conditions by Bond Anion Relay Chemistry: An Efficient Synthesis of Thiazolidin‐2‐ylideneamine

Thiol–yne coupling of propargylamine with isothiocyanate has been developed under metal‐ and solvent‐free conditions. The addition of propargylamine to isothiocyanate gives propargylthiourea. This intermediate in situ undergoes intramolecular 5‐exo‐dig cyclization to give thiazolidin‐2‐ylideneamine. A through‐bond anion relay reaction occurs by attack of the sulfur (not the nitrogen) atom on the alkyne in a highly regioselective manner at ambient temperature. Wide varieties of thiazolidin‐2‐ylideneamine derivatives were formed in excellent yields. Thiol–yne coupling of propargylamine with isothiocyanate has been developed under metal‐ and solvent‐free conditions. The addition of propargylamine to isothiocyanate gives propargylthiourea. This intermediate in situ undergoes intramolecular 5‐exo‐dig cyclization to give thiazolidin‐2‐ylideneamine. Wide varieties of thiazolidin‐2‐ylideneamine derivatives were formed in excellent yields.