Publications by authors named "Ashis Kumar Gupta"

Herein, we report a highly efficient and unprecedented approach for heteroarylation of congested α-bromoamides via electrophilic aromatic substitution of imidazo-heteroarenes and indolizines under mild reaction conditions (room temperature, metal, and oxidant free). The participation of an in situ generated aza-oxyallyl cation as an alkylating agent is the hallmark of this transformation. The method was readily adapted to synthesize novel imidazo-heteroarene-fused dibenzoazepinone architectures of potential medicinal value.

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Over the past decade, the catalysis of N-heterocyclic carbenes has achieved significant advances. In this area, aldehydes, enals, and esters, are commonly employed as starting materials through various catalytic activation modes. However, NHC-activated strategy of amide and its derivatives remains elusive.

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Introduction: The optimal method for fixation of extra-articular distal humerus fractures poses a management dilemma. Although various plate configurations have been proposed, anatomic shaped extra-articular distal humerus locking plates (EADHPs) have emerged as a viable solution for these complex injuries. We assessed functional and radiologic outcomes in our retrospective case series of extra-articular distal humerus fractures managed with these plates at different centers in Cuttack, Odisha.

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An efficient and expedient fluoride-mediated α-selective 1,6-conjugate addition of allenic esters to para-quinone methides has been developed. The reaction exhibited an excellent substrate scope, and a wide range of α-diarylmethylated allenic esters were obtained in good to excellent yields. It was further shown that the strategy could be extended to isatin-derived quinone methides yielding allenic esters containing 3,3-disubstituted oxindoles.

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A 1,6-conjugate addition reaction of the Seyferth-Gilbert reagent (SGR) to p-quinone methides is reported. This base-mediated protocol allows rapid access to diarylmethylated diazomethylphosphonates. The reaction proceeds under mild basic conditions, making it a practical approach for the synthesis of diarylmethylated diazomethylphosphonates with a broad substrate scope.

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An unexpected product-selectivity in the reaction of 2-arylideneindane-1,3-dione with dimethyl diazomethylphosphonate leading to the formation of two different types of products is reported. The reaction carried out in acetone in the presence of catalytic amount of cesium fluoride afforded spiropyrazoline phosphonates via 1,3-dipolar cycloaddition reaction, whereas the reaction in methanol yielded an interesting class of pyrazolylphthalides. This strategy provides an efficient alternative method for the construction of pyrazolylphthalides, and moreover, the process is general, works under mild conditions, and exhibits high functional group compatibility.

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A mild and efficient reaction of the Bestmann-Ohira reagent with N-unprotected isatin-derived olefins has been developed for the selective synthesis of spiro-pyrazoline-oxindoles and tricyclic pyrazoles. The reaction features an attractive product-selectivity depending on the substituent on isatin-derived olefin. Treatment of 3-aryl/alkylideneoxindoles with BOR afforded spiropyrazoline-oxindoles, whereas 3-phenacylideneoxindoles furnished pyrazoloquinazolinones via a unique ring expansion reaction.

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A mild, efficient and rapid domino reaction involving the Bestmann-Ohira reagent (BOR) and α,β-unsaturated aldehydes has been developed for the synthesis of densely functionalized vinylpyrazoles. This reaction demonstrates the dual reactivity of BOR as a homologation reagent as well as a cycloaddition partner, thus constituting a domino reaction in an operationally simple procedure. The application of this efficient synthesis of pyrazoles has been demonstrated for the synthesis of phosphonyl analogues of pyrrolopyrazole alkaloids.

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