Tandem Flavin-Iodine-Catalyzed Aerobic Oxidative Sulfenylation of Imidazo[1,2-<i>a</i>]Pyridines with Thiols

Iida, Hiroki; Demizu, Ryuta; Ohkado, Ryoma

doi:10.1021/acs.joc.8b01878

Cited by 68 publications

(15 citation statements)

References 63 publications

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“…The optimized reaction condition resulted into unsymmetrical thioethers (197 and 198) when applied on differently substituted aryl/heteroaryl (196). Aryl thiols substituted with electron donating as well as withdrawing substitutents tolerated well and resulted into desired product in good to moderate yield.…”

Section: Chemistryselectmentioning

confidence: 99%

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Transition Metal‐Free Sulfenylation of C−H Bonds for C−S Bond Formation in Recent Years: Mechanistic Approach and Promising Future

et al. 2021

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Transition metal‐free sulfenylation of C−H bonds for C−S bond formation has recently emerged as sustainable protocols for the functionalisation of various molecules. Researchers have extensively developed such protocols for the construction of biologically relevant sulfur scaffolds. There has been a gradual shift from metal‐catalyzed to metal‐free C−S bond formation methodologies, because the latter offer environmentally benign and inherently safe access to novel synthetic routes in organic chemistry. The present review offers a dynamic discussion on recent advances in transition metal‐free C−S bond formation via C−H bond functionalization using different surrogate sulfenylating reagents. The review has comprehensively been devoted to radical and ionic mechanistic approaches. Some simple and eco‐friendly reagents for sulfenylation viz. tertbutyl hydrogen peroxide (TBHP), hydrogen peroxide (H2O2), iodine/potassium persulphate (I2/K2S2O8), inorganic bases, strong organic acids, iodine, I2/triphenyl phosphine (PPh3), N‐chlorosuccinamide (NCS), N‐bromosuccinamide (NBS), potassium iodate (KIO3), I2/bovine serum albumin (BSA), tetrabutyl ammonium iodide (TBAI)/HBr and graphene oxide along with their mechanistic approach has been detailed in this review. Moreover, modern methods for the C−S bond formation i. e., biocatalyst, electrochemical and visible light induced sulfenylation, and traditional sulfenylation methodologies have also been incorporated.

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Section: Chemistryselectmentioning

confidence: 99%

“…The molecular iodine was generated by the oxidation of iodide anion by molecular oxygen during Flavin cycle (Scheme 81). [196] …”

Section: Sulfenylationmentioning

confidence: 99%

Transition Metal‐Free Sulfenylation of C−H Bonds for C−S Bond Formation in Recent Years: Mechanistic Approach and Promising Future

et al. 2021

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“…In this context, zinc was found to be an ideal reducing agent in Baeyer-Villiger reactions using flavinium catalyst 22, which is derived from (-)-riboflavin (Scheme 16). 51 Reoxidation of reduced N5-substituted flavinium catalysts with molecular oxygen has since been broadly applied including iodine-mediated reactions, 52 catalytic water oxidation, 53 and catalytic oxygenation of methylrhenium trioxide (MTO). 54…”

Section: Scheme 13mentioning

confidence: 99%

Molecular Editing of Flavins for Catalysis

Rehpenn¹,

Walter²,

Storch³

2021

Synthesis

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The diverse activity of flavoenzymes in organic transformations has fascinated researchers for a long time. However, when applied outside an enzyme environment, the isolated flavin cofactor only shows largely reduced activity. This highlights the importance of embedding the reactive flavin’s isoalloxazine core in defined surroundings. The latter include crucial non-covalent interactions with amino acid side chains or backbone as well as controlled access to reactants such as molecular oxygen. Nevertheless, molecular flavins are increasingly applied in the organic laboratory as valuable organocatalysts. Chemical modification of the parent isoalloxazine structure is of particular interest in this context in order to achieve reactivity and selectivity in transformations, which are so far only known with flavoenzymes or even unprecedented. This review aims to give a systematic overview of the reported designed flavin catalysts and highlights the impact of each structural alteration. It is intended to serve as a source of information when comparing the performance of known catalysts, but also when designing new flavins. Over the last decades, molecular flavin catalysis has emerged from proof-of-concept reactions to increasingly sophisticated transformations. This stimulates anticipating new flavin catalyst designs for solving contemporary challenges in organic synthesis.

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“…[ 5 ] Over the last decade, great achievements have been made on the direct C—H functionalization of imidazo[1,2‐ a ]pyridines. [ 6 ] For instance, the direct amination, [ 7 ] trifluoromethylation, [ 8 ] alkoxylation, [ 9 ] sulfenylation, [ 10 ] selenylation, [ 11 ] and halogenation [ 12 ] have been realized in the past few years. Nowadays, the simple and sustainable production of more structurally diverse C‐3 functionalized imidazo[1,2‐ a ]pyridines is still significantly and enthusiastically pursued.…”

Section: Background and Originality Contentmentioning

confidence: 99%

Recyclable Carbon Nitride Nanosheet‐Photocatalyzed Aminomethylation of Imidazo[1,2‐a]pyridines in Green Solvent

et al. 2021

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Comprehensive Summary An efficient and eco‐friendly carbon nitride nanosheet (NM‐g‐C3N4)‐catalyzed decarboxylative coupling reaction of imidazo‐fused heterocycles (i.e., imidazo[1,2‐a]pyridines, benzo[d]imidazo[2,1‐b]thiazole) with N‐phenylglycines in dimethyl carbonate (DMC) has been developed. The toxic solvents, external oxidants, and restricted reaction conditions could be effectively avoided in this powerful and sustainable protocol. Remarkably, NM‐g‐C3N4 could be straightforwardly recovered by simple centrifugation and recycled and reused at least 7 times without an obvious decrease in catalytic activity.

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Tandem Flavin-Iodine-Catalyzed Aerobic Oxidative Sulfenylation of Imidazo[1,2-a]Pyridines with Thiols

Cited by 68 publications

References 63 publications

Transition Metal‐Free Sulfenylation of C−H Bonds for C−S Bond Formation in Recent Years: Mechanistic Approach and Promising Future

Transition Metal‐Free Sulfenylation of C−H Bonds for C−S Bond Formation in Recent Years: Mechanistic Approach and Promising Future

Molecular Editing of Flavins for Catalysis

Recyclable Carbon Nitride Nanosheet‐Photocatalyzed Aminomethylation of Imidazo[1,2‐a]pyridines in Green Solvent

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