Preparation of 2-[1-Phenyl-1H-pyrazol-5-yl]benzoic Acids from Dilithiated C(α),N-Phenylhydrazones and Methyl Hydrogen Phthalate

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.

Keywords:

• Anion–anion condensations
• multiple anions
• pyrazole–benzoic acids

ACKNOWLEDGMENTS

We thank the following sponsors: the Research Corporation, the National Science Foundation (Grants CHE 9708014 and 0212699 for Research at Undergraduate Institutions) the United States Department of Agriculture, National Research Initiative Competitive Grants Program (2003-35504-12853), and Donors of the Petroleum Research Fund, administered by the American Chemical Society. The College of Charleston LCMS facility was funded by National Institutes of Health Grant P20 RR-016461 from the National Center for Research Resources. The College of Charleston awarded summer grants through its Summer Undergraduate Research Forum (SURF 2006 and 2007) to J. D. Knight and A. C. Dawsey (SURF 2007).