Iodine mediated oxidative cross coupling of 2-aminopyridine and aromatic terminal alkyne: a practical route to imidazo[1,2-<i>a</i>]pyridine derivatives

“…The iodo radical mediated removal of HI gave the corresponding 3‐thiomethylated imidazopyridines ( 53 ) and iodine was regenerated by the oxidation of HI with DMSO (Scheme 17). [115] …”

Section: Sulfenylationmentioning

confidence: 99%

“…It is important to point out here that the thiomethyl radical can be formed by the iodine mediated thermal decomposition of DMSO at higher temperature. This attracted Sumanta and co-workers [115] to extend the scope of developed methodology for the methylthiolation of imidazo[1,2-a]pyridines (13). The developed protocol tolerated well a variety of substituted aromatic terminal alkynes (37).…”

mentioning

confidence: 99%

“…The source of thiomethyl group was confirmed when a reaction of 2-phenylimidazo[1,2a]pyridine (13) and phenylacetylene (37) 53) and iodine was regenerated by the oxidation of HI with DMSO (Scheme 17). [115] Beukeaw and co-workers [116] extended the applicability of iodine by combining it with K 2 S 2 O 8 in a metal-free regioselective C-3 and C-5 sulfenylation of 4-quinolones (54) and uracils (55) respectively (Scheme 18). The optimized condition screened initially with different halogen inducers, oxidizing agents and various solvents was applied successfully to differently substituted 4-quinolones/uracil.…”

mentioning

confidence: 99%

See 1 more Smart Citation

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

et al. 2021

View full text Add to dashboard Cite

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.

show abstract

“…Attributing to its vast applications, this field received tremendous research interest to develop clean and efficient synthetic methodologies for imidazo[1,2- a ]pyridines. ,− The classical methods for the synthesis of imidazo[1,2- a ]pyridines involve cyclocondensation of 2-aminopyridines with α-haloketones or their equivalents, and α,β-unsaturated carbonyl compounds in conventional reaction media . Other notable two-component strategies include reactions between 2-aminopyridines with various coupling partners such as metal-catalyzed oxidative addition of alkynes, nitroalkenes by tandem reactions, oxidative coupling of 1,3-dicarbonyl compounds, and so on . Multicomponent approaches including metal-catalyzed A 3 -coupling reactions, Groebke–Blackburn–Bienaymé reaction, and others provide an atom-economic platform for di- and trisubstituted imidazo[1,2- a ]pyridines.…”

Section: Introductionmentioning

confidence: 99%

Iodine Promoted Efficient Synthesis of 2-Arylimidazo[1,2-a]pyridines in Aqueous Media: A Comparative Study between Micellar Catalysis and an “On-Water” Platform

et al. 2020

View full text Add to dashboard Cite

In a new and environmentally sustainable approach, a series of 2-arylimidazo[1,2-a]pyridine derivatives were synthesized in aqueous media in the presence of iodine as a catalyst. The reaction proceeded by condensation of various aryl methyl ketones with 2-aminopyridines to afford 2-arylimidazo[1,2-a]pyridines in good overall yields. Although several of the reactions were efficiently performed "on water", the addition of a surfactant, namely, sodium dodecyl sulphate , was found effective in terms of substrate scope and yield enhancement. Both methods were successfully used for the gram-scale synthesis of a marketed drug, zolimidine. The simple experimental setup, water as "green" media, and inexpensive catalyst are some of the merits of this protocol.

show abstract

Iodine mediated oxidative cross coupling of 2-aminopyridine and aromatic terminal alkyne: a practical route to imidazo[1,2-a]pyridine derivatives

Abstract: A novel, transition-metal free route leading to imidazo[1,2-a]pyridine derivatives via iodine mediated oxidative coupling between 2-aminopyridine and aromatic terminal alkyne has been demonstrated.

Cited by 38 publications

References 76 publications

Application of DMSO as a methylthiolating reagent in organic synthesis

Application of DMSO as a methylthiolating reagent in organic synthesis

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

Iodine Promoted Efficient Synthesis of 2-Arylimidazo[1,2-a]pyridines in Aqueous Media: A Comparative Study between Micellar Catalysis and an “On-Water” Platform

Contact Info

Product

Resources

About