3-Acylaminopyrazole derivatives via a regioselectively N-protected 3-nitropyrazole

A simple procedure for the selective protection of the endocyclic 1-N of 3-aminopyrazoles as tert-butoxycarbamate (Boc) in good yield is described. A 3-nitropyrazole derivative represents the key intermediate with the nitro substituent determining the regiochemistry of the obtained protected compound. Subsequent acylation at the exocyclic amino group gave rise, after Boc removal, to a series of 3-acylaminopyrazoles in high yields and purities.