A simple new hydrazine-free synthesis of methyl 1,4,5-trisubstituted 1H-pyrazole-3-carboxylates

Conditions for successful syntheses of poly- substituted pyrazole-3-carboxylates have been found. The methodology consists in mixing equimolar amounts of diazonium tetrafluoroborates and enaminoesters in pres- ence of sodium acetate. 1-Methylpyrrolidone has appeared to be the solvent of choice. The compounds prepared have been characterized by means of nuclear magnetic reso- nance (NMR) spectroscopy, elemental analysis, and in two cases, also by X-ray diffraction. The advantage of the methodology is a simple implementation without necessity of working under inert atmosphere. The presence of other functional groups enables further synthetic transformations of the products