New Synthesis and Reactions of Ethyl 5-amino-4-cyano-1-phenyl-1H-pyrazole-3-carboxylate

Synthesis of ethyl 5‐amino‐4‐cyano‐1‐phenyl‐1H‐pyrazole‐3‐carboxylate 5 has been achieved via abnormal Beckmann rearrangement of o‐chloroaldehyde 1. Reaction of o‐aminocarbonitrile 5 with concentrated H2SO4 furnished expected o‐aminocarboxamide pyrazole 6. Key intermediates o‐aminocarbonitrile 5 and o‐aminocarboxamide 6 were successfully utilized for the synthesis of pyrazolopyrimidine derivatives. The replacement of Cl in o‐chlorocarbonitrile 3 with secondary amine furnished new synthon 13, which was further used for the synthesis of polysubstituted heterocycles. The obtained new products were well characterized by IR, 1H and 13C NMR, and mass spectra.