Browsing by Author "Sandip Kumar Tiwari"

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Direct Arylation of Distal and Proximal C(sp3)-H Bonds of t-Amines with Aryl Diazonium Tetrafluoroborates via Photoredox Catalysis
(American Chemical Society, 2021) Pradip Kumar Mondal; Sandip Kumar Tiwari; Pushpendra Singh; Ganesh Pandey
A visible light-mediated arylation protocol for t-amines has been reported through the coupling of γ- and α-amino alkyl radicals with different aryl diazonium salts using Ru(bpy)3Cl2·6H2O as a photocatalyst. Structurally different 9-aryl-9,10-dihydroacridine, 1-aryl tetrahydroisoquinoline, hexahydropyrrolo[2,1-a]isoquinoline, and hexahydro-2H-pyrido[2,1-a]isoquinoline frameworks with different substitution patterns have been synthesized in good yield using this methodology. © 2021 American Chemical Society.
Intramolecular Cyclization of -COY (Y = OH, NHPh) to Photoredox Functionalized Benzylic C(sp3)-H Bond. Attractive Approach to Construct γ, δ-lactones and lactams Scaffolds
(John Wiley and Sons Inc, 2024) Kumari Swati Sharma; Sandip Kumar Tiwari; Ganesh Pandey
Synthesis of γ and δ-lactones and lactams are reported in high yield by the cyclization of −COY (Y=OH, NHPh) to the photo redox functionalized benzylic C(sp3)−H bond. © 2024 Wiley-VCH GmbH.
P-Silylation of Arenes via Organic Photoredox Catalysis: Use of p-Silylated Arenes for Exclusive o-Silylation, o-Acylation, and o-Alkylation Reactions
(American Chemical Society, 2021) Ganesh Pandey; Sandip Kumar Tiwari; Pushpendra Singh; Pradip Kumar Mondal
Photocatalytic regiospecific p-silylation of arenes has been achieved by the coupling of in situ generated silyl radical with arene radical cation. The strategy involves reductive activation of PhSe-SiR3 and single electron transfer from the electron rich arene to 9,10-dimethoxyanthracene radical cation (DMA•+). p-Silyl arenes, thus formed, are further utilized for exclusive o-silylation reaction and for regiospecific o-acylation as well as o-alkylation reaction. © 2021 American Chemical Society.
Silver(I)-Catalyzed Regioselective Synthesis of Dihydrofuro[3,4-b]quinolines from o-Alkynylquinoline-MBH Adducts and Evaluation of their Photophysical Properties
(Wiley-VCH Verlag, 2020) Vipin Kumar; Sandip Kumar Tiwari; Virender Singh
A simple and facile approach is described for the regioselective synthesis of dihydrofuro[3,4-b]quinolines from ortho-alkynylquinoline-Morita-Baylis-Hillman adducts under mild reaction conditions. Interestingly, in case of aromatic alkynes, 5-exo-dig cyclization was observed, while in case of aliphatic long chain alkynes, 6-endo-dig cyclized products were obtained. The present approach does not require any dry conditions, tedious work-up or inert atmosphere for the production of dihydrofuro[3,4-b]quinolines. The exact structures and stereochemistry of the synthesized molecules were assigned by NMR and X-ray crystallographic analysis. Their photophysical properties were also evaluated. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim