Direct Alkynylation of 3H-Imidazo[4,5-b]pyridines Using gem-Dibromoalkenes as Alkynes Source

Aziz, Jessy; Baladi, Tom; Piguel, Sandrine

doi:10.1021/acs.joc.6b00406

Cited by 28 publications

(10 citation statements)

References 64 publications

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“…A direct C-2 alkynylation of 3 H -imidazo[4,5- b ]pyridines 426 was reported by the group of J. Aziz. The group has used Cu(OAc) 2 or CuBr·SMe 2 (copper bromide in a dimethyl sulfide complex) as catalyst depending upon the nature of substituents present on the reacting substrates [197]. The reaction involved DPEphos as a phosphine ligand and LiO t- Bu as a base in 1,4-dioxane at 120 °C (Scheme 140).…”

Section: Reviewmentioning

confidence: 99%

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

Reen

Kumar

Sharma

2019

Beilstein J. Org. Chem.

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A comprehensive account of recent advances in the synthesis of imidazopyridines, assisted through transition-metal-catalyzed multicomponent reactions, C–H activation/functionalization and coupling reactions are highlighted in this review article. The basic illustration of this review comprises of schemes with concise account of explanatory text. The schemes depict the reaction conditions along with a quick look into the mechanism involved to render a deep understanding of the catalytic role. At some instances optimizations of certain features have been illustrated through tables, i.e., selectivity of catalyst, loading of the catalyst and percentage yield with different substrates. Each of the reported examples has been rigorously analyzed for reacting substrates, reaction conditions and transition metals used as the catalyst. This review will be helpful to the chemists in understanding the challenges associated with the reported methods as well as the future possibilities, both in the choice of substrates and catalysts. This review would be quite appealing to a wider range of organic chemists in academia and industrial R&D sectors working in the field of heterocyclic syntheses. In a nutshell, this review will be a guiding torch to envisage: (i) the role of various transition metals in the domain dedicated towards method development and (ii) for the modifications needed thereof in the R&D sector.

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Section: Reviewmentioning

confidence: 99%

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

Reen

Kumar

Sharma

2019

Beilstein J. Org. Chem.

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“…We also developed a copper-catalyzed direct C-2 alkynylation of imidazo[4,5-b]pyridines 114 using gem-dibromoalkenes as coupling partners (Scheme 46). 68 These latter are readily available and more stable than the correspondent halogenated alkynes. A large excess of base (LiOtBu) was essential for the progress of the reaction; a part for the dehydrobromination of the dibromoalkene and another part for the deprotonation of C-2.…”

Section: Short Review Syn Thesismentioning

confidence: 99%

An Update on Direct C–H Bond Functionalization of Nitrogen-Containing Fused Heterocycles

Aziz

Piguel

2017

Synthesis

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This report highlights the recent advances in direct C–H bond functionalization of 5,5- and 6,5-fused heterocycles containing at least two nitrogen atoms. Besides C–C bond formation, C–N, C–S, C–P, and C–Si bonds can also be created via a metal-catalyzed process. Some examples, where a C–H functionalization approach was applied for the synthesis of drug candidates, will be presented as well.1 Introduction2 C–H Functionalization Reactions of N-Containing Heterocycles2.1 Imidazo[1,2-a]pyridines2.2 Pyrrolo[1,2-a]pyrazines2.3 Imidazo[1,2-b]pyrazoles2.4 Imidazo[1,2-a]pyrimidines2.5 Imidazo[1,2-a]pyrazines and Imidazo[1,5-a]pyrazines2.6 Imidazo[1,2-b]pyridazines2.7 Imidazo[4,5-b]pyridines and Imidazo[4,5-c]pyridines2.8 Pyrazolo[3,4-b]pyridines2.9 Pyrazolo[1,5-a]pyrimidines2.10 Pyrrolo[2,3-d]pyrimidines and Pyrrolo[3,2-d]pyrimidines2.11 Imidazo[1,2-b][1,2,4]triazines2.12 Imidazo[1,2-b][1,2,4,5]tetrazines3 Outlook4 Conclusion

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“…Various transition-metal catalysts have been known for the C–H bond alkynylation of different arenes and heteroarenes, including indoles . Specifically, the earth-abundant and inexpensive 3d metals, such as Fe, Co, Ni, Cu have been successfully employed for the alkynylation of activated azoles and benzamides, and been found to be more beneficial. Shi and Ackermann have individually shown the C-2 alkynylation of indoles by cobalt catalysis employing different alkynyl coupling partners.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Nickel(II)-Catalyzed C(2)–H Alkynylation of Indoles with Alkynyl Bromide

Khake

Jain²,

Patel

et al. 2018

Organometallics

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The nickel system (THF)2NiBr2/phen has recently been shown as an efficient catalyst for the C–H bond alkynylation of diverse heteroarenes with (triisopropylsilyl)alkynyl bromide via monodentate chelation assistance. Herein, we report an extensive mechanistic investigation for the direct alkynylation of indoles involving the well-defined nickel catalyst, which features a coordinative insertion pathway of alkynyl bromide with the Ni(II) catalyst. Catalytic relevant nickel complexes, (phen)NiCl2 (5), (phen)2NiCl2 (6) and [(phen)3Ni]·NiCl4 (7) were isolated, and the complexes 6 and 7 were structurally characterized. Well-defined complexes were as competent as the in situ generated catalyst system (THF)2NiBr2/phen for the alkynylation of indoles. Various controlled studies and reactivity experiments were performed to understand the probable pathway for the alkynylation reaction. Kinetics analysis highlights that the complex (phen)NiX2 acts as a precatalyst, and the involvement of substrate indole and LiO t Bu are essential for the generation of the active catalyst. Deuterium labeling and kinetic studies suggest that the process involving C–H cleavage and carbo-nickelation of indole is a crucial rate influencing step. Reactivity study of various alkynyl compounds with nickel-species highlights a migratory insertion route for the reaction. DFT calculations firmly support the experimental findings and suggest the coordinative insertion pathway of alkynyl bromide rather than oxidative addition toward the nickel(II) center.

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Direct Alkynylation of 3H-Imidazo[4,5-b]pyridines Using gem-Dibromoalkenes as Alkynes Source

Cited by 28 publications

References 64 publications

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

An Update on Direct C–H Bond Functionalization of Nitrogen-Containing Fused Heterocycles

Mechanism of Nickel(II)-Catalyzed C(2)–H Alkynylation of Indoles with Alkynyl Bromide

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