Rearrangement of 3,3-Disubstituted 1-Aryl-4,5-dihydro-5-oxo-3H-1,2,4-triazolium Tetrafluoroborates; Part 2. A Convenient Synthesis of 1,5-Annulated 1,2-Dihydro-2-phenyl-3H-1,2,4-triazol-3-ones
Preparation of 2-[1-Phenyl-1<i>H</i>-pyrazol-5-yl]benzoic Acids from Dilithiated<i>C</i>(α),<i>N</i>-Phenylhydrazones and Methyl Hydrogen Phthalate
作者:Anna C. Dawsey、John D. Knight、Charles F. Beam、N. Dwight Camper
DOI:10.1080/00397910802323049
日期:2008.11.3
Abstract Select C(α),N-phenylhydrazones were dilithiated with excess lithium diisopropylamide to their dianion-type intermediates followed by condensation with methyl hydrogen phthalate. The resulting C-acylated hydrazones were not isolated but acid cyclized directly to afford new substituted 2-(1-phenyl-1H-pyrazol-5-yl)benzoic acids.
A highly selective and efficient method for the synthesis of 5-trifluoromethylated and 5-perfluoroalkylated pyrazoles has been developed which relies on the cyclization of hydrazine dianions with ethyl perfluorocarboxylates. The pyrazoles prepared were evaluated as potential inhibitors of alkaline phosphatases, namely human tissue non-specific alkaline phosphatase (h-TNAP) and tissue specific intestinal