Selective ring N-protection of aminopyrazoles

Two simple Procedures for the selective protection of the ring N of aminopyrazoles as tert-butoxycarbamate (Boc) in high yields are reported: several other protecting groups (Cbz, Bn. SEM) can be introduced using the one-pot procedure (method B). The N-Boc protected aminopyrazoles are acylated at the exocyclic NH2 group and subsequently deprotected to give the corresponding 3-acylaminopyrazoles in high yields. This procedure is applicable for the rapid parallel synthesis of 3-acylaminopyrazoles. (C) 2003, Elsevier Science Ltd. All rights reserved.