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 condition. The addition of propargylamine on isothiocyanate gives propargylthiourea. This intermediate in situ undergoes intramolecular 5-exo-dig cyclization to give thiazolidin-2-ylideneamine. This through bond anion relay reaction occurs by attack of sulphur (not nitrogen) on alkyne in highly regioselective manner at ambient temperature. Wide varieties of thiazolidin-2-ylideneamine derivatives were formed in excellent yields.