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α‐Aryl‐β,β‐Ditosyloxy Ketones as Versatile Precursors: Convenient, Direct, Metal‐free and Regioselective Synthesis of 4,5‐Diaryl/1,4,5‐Triaryl Pyrazoles

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Efficient and more practical unified approach for construction of 4,5-diaryl/1,4,5-triaryl pyrazoles using α-aryl-β,β-ditosyloxy ketones as key precursors has been developed. α-Aryl-β,β-ditosyloxy ketones behaves like β-ketoaldehydes to binucleophilic reagents.


Abstract

The present study demonstrate the synthetic applications of α-aryl-β,β-ditosyloxy ketones 3 as 1,3-dielectrophilic three carbon atom versatile precursors to synthesize scarcely underexplored 4,5-diaryl/1,4,5-triaryl pyrazoles as small aza-heterocycles. The exact regiochemistry around pyrazole nucleus has been confirmed by single crystal XRD analysis along with spectroscopic data (1H & 13C-NMR, IR) and HRMS analysis. The single crystal-XRD analysis exposed that, crystallization of 4,5-diaryl pyrazoles 5 b in trigonal systems with R-3 space group. The strategy was found advantageous especially owing to (i) operationally simplicity of procedure (ii) high regioselectivity (iii) less reaction timing (iv) versatile reactivity due to presence of two p-toluenesulfonyloxyl groups which behaves as excellent leaving group as well as electron withdrawing group. Additionally, we conjectured that present methodology can broaden the aspects of synthetic chemistry in ongoing medicine chemistry programs for designing and synthesis of regioisomeric analogues of some well-recognised drugs like celecoxib.

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