Synthesis of Novel Bis-pyrazoles via Electrophilic Cyclization

Efficient steps towards the synthesis of novel (phenyl)(1'-aryl-1,5,5'-triphenyl[3,3'-bi-1H-pyrazol]-4-yl) methanones 4a-e were developed. The procedure starts from 1-(4-benzoyl-1,5-diphenyl-1H-3-pyrazolyl)-3-phenyl-2-propyn-1-one (2) which was synthesized by a palladium catalyzed crosscoupling reaction. Compound 2 reacted with various hydrazines to give (E)-(phenyl)[1,5-diphenyl-3-[3-phenyl-1-(2-arylhydrazono)-2-propyn-1-yl]-1H-4-pyrazolyl] methanones E-3a-e. The bis-pyrazole derivatives 4a-e were synthesized from electrophilic cyclization reaction of alpha, beta-acetylenic hydrazones E-3a-e and copper(I) iodide. All synthesized compounds were characterized by FT-IR, H-1,C-13 NMR and Mass spectral analyses.