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Issue 47, 2018, Issue in Progress
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Direct N-heterocyclization of hydrazines to access styrylated pyrazoles: synthesis of 1,3,5-trisubstituted pyrazoles and dihydropyrazoles

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Abstract

A microwave-assisted method has been developed for the synthesis of tri-substituted pyrazoles via direct N-heterocyclization of hydrazines with metal-acetylacetonate and -dibenzylideneacetonate without using any base or additives. Most importantly, the synthesis of 1-aryl-5-phenyl-3-styryl-1H-pyrazoles was achieved in a single step using hydrochloride salt of various phenylhydrazines and this is the first report for direct construction of these molecules. The reaction medium and microwave conditions play a critical role for their selective product formation during the reaction. The present reaction explored the usage of metal-diketonic complexes as reaction substrates providing acetylacetone and dibenzylideneacetone moieties to directly participate in cyclization with hydrazines to form the corresponding pyrazoles in excellent yields. The present protocol introduces the important N-heterocyclic moieties in the final structures, giving the reaction great applications from a medicinal chemistry perspective, particularly in the late stage modification strategies in drug discovery.

Graphical abstract: Direct N-heterocyclization of hydrazines to access styrylated pyrazoles: synthesis of 1,3,5-trisubstituted pyrazoles and dihydropyrazoles

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Publication details

The article was received on 28 May 2018, accepted on 02 Jul 2018 and first published on 24 Jul 2018


Article type: Paper
DOI: 10.1039/C8RA04550J
RSC Adv., 2018,8, 26523-26527
  • Open access: Creative Commons BY-NC license
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    Direct N-heterocyclization of hydrazines to access styrylated pyrazoles: synthesis of 1,3,5-trisubstituted pyrazoles and dihydropyrazoles

    V. Venkateswarlu, J. Kour, K. A. A. Kumar, P. K. Verma, G. L. Reddy, Y. Hussain, A. Tabassum, S. Balgotra, S. Gupta, A. D. Hudwekar, R. A. Vishwakarma and S. D. Sawant, RSC Adv., 2018, 8, 26523
    DOI: 10.1039/C8RA04550J

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