ChemInform Abstract: Regioselective Synthesis of 1,3,5‐ and 1,3,4,5‐Substituted Pyrazoles via Acylation of N‐Boc‐N‐Substituted Hydrazones.

Abstract

Regioselective Synthesis of 1,3,5-and 1,3,4,5-Substituted Pyrazoles via Acylation of N-Boc-N-Substituted Hydrazones. -Acylation of title hydrazones, e.g. (I), proceeds with either acyl chlorides or esters (II) to give hydrazones which undergo TFA-promoted cyclization to pyrazoles like (IV). A wide range of tri-and tetra-substituted pyrazoles is obtained. Regioisomers are accessible by proper choice of substrates [cf. (IVd) and (VII)]. -(TINARELLI, A.; RIGHI*, P.; ROSINI, G.; ANDREOTTI, D.; PROFETA, R.; SPADA, S.; Tetrahedron 67 (2011) 3, 612-617, http://dx.