Solid-Phase Synthesis of 5-Amino-1-(Substituted Thiocarbamoyl)pyrazole and 1,2,4-Triazole Derivatives via Dithiocarbazate Linker

A general method is reported for the parallel solid-phase synthesis of 5-amino-1-(substituted thiocarbamoyl)pyrazole and 1,2,4-triazole derivatives based on the cyclization of polymer-bound dithiocarbazate 3 with various electrophiles, such as 3-ethoxyacrylonitriles 8 and cyanocarboimidates 9. The polymer-bound dithiocarbazate 3, produced by nucleophilic reaction with carbon disulfide and Fmoc-hydrazine on the Merrifield resin, served as the key intermediate for subsequent heterocycle diversification. Further nucleophilic substitution on these polymer-bound 5-amino-1-dithiocarboxypyrazoles 4 and 1,2,4-triazoles 6 with various amines under thermal cleavage condition produced the desired 5-amino-1-(substituted thiocarbamoyl)pyrazoles 5 and 1,2,4-triazoles 7. The progress of reactions could be monitored as polymer-bound intermediates by ATR-FTIR spectroscopy on single bead. The final compounds, obtained in good four-step overall yields and high purities upon cleavage from the resins, were characterized by LC/MS, 1H NMR, and 13C NMR spectroscopy.