Browsing by Author "Anup Kumar Yadav"

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Aromatic C(sp2)−H Functionalization by Consecutive Paired Electrolysis: Dibromination of Aryl Amines with Dibromoethane at Room Temperature
(John Wiley and Sons Inc, 2024) Gaurav Shukla; Malkeet Singh; Anup Kumar Yadav; Maya Shankar Singh
Herein, we disclose a facile and efficient electrochemical method for the dibromination of aryl amines by double functionalization of aromatic C(sp2)−H (both para and ortho) under metal- and external oxidant-free conditions at room temperature for the first time. The reaction is demonstrated using 1,2-dibromoethane to dibrominate a wide range of N-substituted aryl amines in a simple setup with C(+)/Pt(−) electrodes under mild reaction conditions. This transformation proceeds smoothly with a broad substrate scope affording the valuable and versatile N-substituted 2,4-dibromoanilines in moderate to excellent yields with high regioselectivity. In this paired electrolysis, cathodic reduction of 1,2-DBE followed by anodic oxidation generates bromonium intermediates, which then couple with anilines to furnish the dibrominated products. It represents a distinctive approach to challenging redox-neutral reactions. The versatility of the electrochemical ortho-, para-dibromination was reflected by unique regioselectivities for challenging aryl amines and gram-scale electrosynthesis without the use of a stoichiometric oxidant or an activating agent. © 2023 Wiley-VCH GmbH.
Electronically-controlled diastereoselective synthesis of spirocycles via [4 + 2] cycloaddition of 2-arylidene-1-indenones with benzyne
(Royal Society of Chemistry, 2023) Subhasish Ray; Anup Kumar Yadav; Saurabh Singh; Monish Arbaz Ansari; Maya Shankar Singh
A one-pot electronically controlled [4 + 2] cycloaddition reaction of in situ generated benzyne with 2-arylidene-1-indenone is unveiled to construct novel spirocyclic frameworks in a regio- and diastereoselective fashion. This protocol features operational simplicity, good functional group tolerance and avoids the use of metal catalysts and external additives. This methodology has extended the synthetic application of 2-arylidene-1-indenones enabling easy access to valuable 10′H-spiro[indene-2,9′-phenanthren]-1(3H)-ones in good yields. © 2023 The Royal Society of Chemistry.
Metal-Free α-Sulfonylation of β-Ketothioamides: Access to α-Sulfonyl-β-Ketoamides and their Photophysical Studies
(John Wiley and Sons Inc, 2025) Vipin Kumar; Monish Arbaz Ansari; Anup Kumar Yadav; Saurabh Singh; Krishanu Bandyopadhyay; Satyen Saha; Maya Shankar Singh
Herein, we report a metal and additive-free unprecedented reactivity of β-ketothioamides with sulfonyl chlorides for the synthesis of previously unreported 2-sulfonyl-3-oxo-N,3-diarylpropanamides via in situ thioamide to amide conversion followed by dehydrohalogenative C−S cross-coupling at room temperature under an open air for the first time. The protocol demonstrates not only its operational simplicity, efficiency, mild condition, and scalability, but also easy to get the diverse a-sulfonyl-β-ketoamides in good to high yields. Additionally, the DFT and photophysical studies supported the proposed mechanism, and revealed unique excitation-dependent emission coupled with ESPT for the synthesized sulfones. © 2024 Wiley-VCH GmbH.
One-Pot Access to Tetrasubstituted 2-Aminothiophenes via Regio- and Chemoselective Domino Reactions of Dithioesters with Fumaronitrile at Room Temperature
(John Wiley and Sons Inc, 2023) Anup Kumar Yadav; Vipin Kumar; Pragya Pali; Subhasish Ray; Abhineet Verma; Maya Shankar Singh
Herein, we report a one-pot viable protocol to synthesize tetrasubstituted 2-aminothiophenes engaging readily accessible α-enolic dithioesters and abundant fumaronitrile under transition metal-free conditions at room temperature in open air. The reaction proceeds via successive Michael-type addition/intramolecular cyclization/isomerization cascades. The added features are benign conditions, exclusive regio- and chemoselectivity, excellent atom-/step-economy, easy purification, and tolerance of wide range of functional groups of a diverse electronic and steric nature. This protocol not only provided a robust and modular approach to various 2-aminothiophenes in moderate to excellent yields, but also demonstrated the potential of dithioesters and fumaronitrile in the challenging intermolecular cross-coupling reactions widening the arsenal of synthetic methods. © 2023 Wiley-VCH GmbH.
PIDA-promoted metal-free [3 + 2] heteroannulation of β-ketothioamides with 4-hydroxy coumarins: chemo-/regioselective access to furo[3,2-c]chromen-4-ones at room temperature
(Royal Society of Chemistry, 2024) Anup Kumar Yadav; Dhananjay Yadav; Vipin Kumar; Subhasish Ray; Maya Shankar Singh
Herein, we report a viable protocol to access furo[3,2-c]chromen-4-ones by engaging easily accessible 4-hydroxy coumarins as a three-atom CCO unit and thioamides as a C2 coupling partner, mediated by phenyliodine(iii) diacetate (PIDA) at room temperature in a highly efficient and pot-/step-economical manner. This strategy not only avoids potential toxicity and tiresome workup conditions, but also features operational simplicity, a broad substrate scope, good functional group tolerance, high yields, easy scalability and exclusive selectivity. A mechanistic study has shown that this metal-free reaction is triggered by PIDA via activation of the β-carbon of 4-hydroxy coumarin, followed by a nucleophilic addition/intramolecular cyclization/dethiohydration cascade. High-resolution mass spectra (HRMS) study confirms the key intermediates involved during the course of the reaction, elucidating the reaction pathways, and demonstrates the excellent regio- and chemoselectivity of this approach. © 2024 The Royal Society of Chemistry.
Synthesis of pyrrolo[3,4-c]pyridines via metal-free cross-coupling/cyclization cascades of β-ketothioamides with 2-aroylmalononitrile at room temperature
(Royal Society of Chemistry, 2025) Anup Kumar Yadav; Vipin Kumar; Saurabh Singh; Subhasis Samai; Maya Shankar Singh
We herein report a metal-free, chemo- and site-selective strategy to synthesize pyrrolo[3,4-c]pyridines using β-ketothioamides and 2-aroylmalononitrile at room temperature in open air. The base-assisted approach proceeds through cross-coupling/two-fold intramolecular cyclization cascades enabling direct access to pyrrolo-fused pyridines via sequential formation of C–N, C⚌O, C–C and C–N bonds. The O2 as a green oxidant, scalability and H2O as a sole by-product are the additional benefits. This journal is © The Royal Society of Chemistry, 2025
Transition-Metal Free Chemoselective C(sp3)–S Cross-Coupling/ Cyclization Cascade: Reagent-Controlled Divergent Synthesis of Methylene-functionalized Thiazolidines and 1,3-Thiazinanes
(Georg Thieme Verlag, 2025) Vipin Kumar; Anup Kumar Yadav; Saurabh Singh; Maya Shankar Singh
A highly chemoselective consecutive cross-coupling/cyclization cascade of β-ketothioamides with dihaloalkanes has been achieved under transition-metal free condition, enabling the formation of methylene-functionalized thiazolidines and 1,3-thiazinanes at room temperature in open air in high yields. The typical features of this straightforward sustainable approach include readily accessible starting materials, simple one-pot operation, atom-/step-economy, cost-effective, good substrate scope, and scalability. Noteworthy, HX is the only by-product, and stereochemistry of the exocyclic methylene moiety was assigned to have Z-configuration. Late-stage functionalization could provide new opportunities for the discovery of N, S-heterocyclic drugs, and other potential functional molecules. © 2025. Thieme. All rights reserved.