Department of Chemistry

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Author: search.filters.author.Kumar, AnilSubject: search.filters.subject.Chemical reactions

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Now showing 1 - 6 of 6
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    Phenyliodine(III) Diacetate-Mediated 1,2-ipso-Migration in Mannich Bases of Imidazo[1,2-a]pyridines: Preparation of N-Acetoxymethyl/Alkoxymethyl-N-arylimidazo[1,2-a]pyridine-3-amines
    (ACS, 2020-05) Kumar, Anil
    Phenyliodine(III) diacetate -mediated 1,2-ipso-migration of an imidazo[1,2-a]pyridine ring via the formation of an aziridine intermediate in Mannich bases derived from imidazo[1,2-a]pyridines, 2-pyridylamines or arylamines, and formaldehyde is reported. The imidazo[1,2-a]pyridines bearing different substituents showed excellent migratory aptitude and resulted in corresponding N-acetoxymethyl-, N-alkoxymethyl-, and N-hydroxymethyl-N-arylimidazo[1,2-a]pyridine-3-amine derivatives in moderate to excellent (42 examples; 35–93%) yields. Radical trapping experiments confirmed the involvement of a non-radical intermediate. The developed protocol is amenable for a scale-up reaction, and synthetic utility of N-acetoxymethyl products was demonstrated by transforming them to corresponding N-(pyridin-2-yl)imidazo[1,2-a]pyridin-3-amines
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    Mechanochemical Ruthenium-Catalyzed Ortho-Alkenylation of N-Heteroaryl Arenes with Alkynes under Ball-Milling Conditions
    (ACS, 2022-04) Kumar, Anil
    The mechanochemical, solvent-free Ru(II)-catalyzed alkenylation of N-heteroaryl arenes with alkynes has been successfully described. A wide spectrum of arenes bearing N-heteroaryl moieties such as imidazo[1,2-a]pyridine, imidazo[1,2-a]pyrimidine, benzo[d]imidazo[2,1-b]thiazole, imidazo[2,1-b]thiazole, 2H-indazole, 1H-indazole, 1H-pyrazole, and 1,2,4-oxadiazol-5(4H)-one as a directing group reacted with various substituted alkynes under ball milling in the presence of [Ru(p-cymene)Cl2]2, affording dialkenylated products in moderate to good yields. The reaction of 2,3-dihydrophthalazine-1,4-dione with 1-phenyl-1-propyne afforded a monoalkenylated product. Similarly, reaction of 2-phenylimidazo[1,2-a]pyridine with aliphatic terminal alkynes produced a monoalkenylated derivative as the major product along with minor amount of dialkenylated product. The developed method exhibited excellent functional group compatibility, broad substrate scope, shorter reaction times, and no external heating. Moreover, the method can be readily scaled-up as demonstrated by gram-scale synthesis of 2-(2,6-bis((E)1-phenylprop-1-en-2-yl)phenyl)imidazo[1,2-a]pyridine.
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    Synthesis of Ionic Liquid-Supported Sulfonyl Azide and Its Application in Diazotransfer Reaction
    (ACS, 2012) Kumar, Anil
    The paper describes synthesis of a novel ionic liquid-supported sulfonyl azide and its applications as diazotransfer reagent of active methylene compounds as well as deformylative diazo transfer reagent. The diazo compounds were isolated in excellent yields (82–94%) and high purity. The method offers better separation of product and reagent. This method is experimentally simple and mild, and requires very short reaction time.
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    Dual Role of Glyoxal in Metal-Free Dicarbonylation Reaction: Synthesis of Symmetrical and Unsymmetrical Dicarbonyl Imidazoheterocycles
    (ACS, 2019-06) Kumar, Anil
    A practical and efficient method has been developed for the dicarbonylation of imidazoheterocycles using glyoxals as dicarbonyl precursors under metal-free conditions in acetic acid. A series of symmetrical and unsymmetrical dicarbonyl imidazoheterocycles was synthesized in good yields. Aryl and alkyl glyoxals also demonstrated excellent reactivity under similar reaction conditions and delivered corresponding dicarbonyl imidazoheterocycles in high yields. It is believed that the glyoxal plays a dual role both as a dicarbonyl source and as an oxidant in this transformation. A probable mechanistic pathway has been proposed based on control experiments and electrospray ionization high-resolution mass spectrometry analysis.
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    Rhodium(III)-Catalyzed Dehydrogenative Annulation and Spirocyclization of 2-Arylindoles and 2-(1H-Pyrazol-1-yl)-1H-indoles with Maleimides: A Facile Access to Isogranulatimide Alkaloid Analogues
    (ACS, 2021) Kumar, Anil; Kumar, Dalip
    A Rh(III)-catalyzed dehydrogenative annulation and spirocyclization of 2-arylindoles and 2-(1H-pyrazol-1-yl)-1H-indole with maleimides is described. The cascade protocol provided highly functionalized benzo[a]pyrrolo[3,4-c]carbazole-1,3(2H,8H)-diones and spiro[isoindolo[2,1-a]indole-6,3′-pyrrolidine]-2′,5′-diones in good to excellent. The developed reaction methodology exhibited broad substrate scope with good functional group tolerance and is operationally simple and scalable. Photophysical properties of the annulated products were investigated. The annulated product of 2-(1H-pyrazol-1-yl)-1H-indole showed high absorption and emission values with a large red-shift as compared to that of 2-phenylindole.
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    TEMPO-Mediated Cross-Dehydrogenative Coupling of Indoles and Imidazo[1,2-a]pyridines with Fluorinated Alcohols
    (ACS, 2021) Kumar, Anil
    A simple and highly efficient metal-free method has been developed for hydroxyfluoroalkylation of indoles and imidazo[1,2-a]pyridines via TEMPO-mediated C(sp3)–H and C(sp2)–H bond cross-dehydrogenative coupling of fluorinated alcohols and indoles. The protocol showed broad substrate scope, afforded good yields of hydroxyfluoroalkylated products, and was amenable for scale-up. Mechanistic investigation indicated involvement of the radical pathway.