Copper(II)‐Catalyzed One‐Pot Synthesis of Thiazolidin‐2‐imines and Formamides Using Vilsmeier Reagent

Facile synthetic routes for the conversion of a series of N ‐aryl propargylamines to thiazolidin‐2‐imines and formamides are described. A cross‐linked chitosan‐supported copper(II) biocomposite (CS‐PDB@Cu(NO 3 ) 2 ) was employed as a heterogeneous catalyst in a one‐pot multicomponent reaction involving primary amines, formaldehyde, terminal alkynes, and isothiocyanates in toluene, yielding thiazolidin‐2‐imines in moderate to good yields (25%–70%) via N ‐aryl propargylamine intermediates. Additionally, N ‐formylation of N ‐aryl propargylamines using the Vilsmeier reagent afforded formamides in high yields (70%–88%). A total of 20 thiazolidin‐2‐imine derivatives and 22 formamide derivatives were successfully isolated. All isolated products were characterized by 1 H and 13 C { 1 H} NMR and HRMS spectroscopy. The CS‐PDB@Cu(NO 3 ) 2 biocomposite catalyst was recyclable for up to three catalytic cycles through simple filtration. Reaction intermediates for both transformations were identified by LC‐MS analysis. Furthermore, the structures of two thiazolidin‐2‐imine compounds, 4h and 4t , were unambiguously confirmed by single‐crystal X‐ray crystallography.