Facile and Efficient Regioselective Synthesis of 1-(3′-Substituted Quinoxalin-2′-yl)-3-aryl/heteroaryl-5-methylpyrazoles

Abstract

This report describes an efficient and practical approach for regioselective synthesis of 1-(3′-substituted quinoxalin-2′-yl)-3-aryl/heteroaryl-5-methylpyrazoles (3a–j). Reaction of 2-chloro-3-substituted quinoxalines (1) with 3(5)-methyl-5(3)-aryl-1H-pyrazoles (2) in the presence of sodium hydride furnished the title compounds in excellent yields with good levels of regioselectivity. The present protocol is superior to the existing method, which yielded a mixture of regioisomeric pyrazoles (I, II) and triazolo[4,3-a]quinoxalines (III).

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GRAPHICAL ABSTRACT

Keywords:

• 2-Chloro-3-substituted quinoxalines
• 3(5)-methyl-5(3)-aryl-1h-pyrazoles
• regioselective synthesis
• 1-(3′-substituted quinoxalin-2′-yl)-3-aryl/heteroaryl-5-methylpyrazoles

ACKNOWLEDGMENTS

We are thankful to the Council of Scientific and Industrial Research (CSIR), New Delhi, India, for providing financial assistance to Eakta Masan. We also thank the Mass Spectrometry Facility, University of California, San Francisco, USA, for running the mass spectra. Thanks are also due to SAIF, CDRI, Lucknow for elemental analysis.