A sequential synthesis of substituted furans from aryl alkynes and ketones involving a cerium(IV) ammonium nitrate (CAN)-mediated oxidative cyclization

Undeela, Sridhar; Ramchandra, Joshi P.; Menon, Rajeev S.

doi:10.1016/j.tetlet.2014.08.039

Cited by 17 publications

(8 citation statements)

References 37 publications

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“… In this case, intermediate potassium dienolates cyclize to give dihydrofurans, which further aromatize to form furans 21a and 21b . Later, furans 21 were prepared in two steps, namely, the synthesis of β,γ-ethylenic ketones and their oxidative cyclization in the (NH 4 ) 2 Ce(NO 3 ) 6 /KBr system (Scheme ).…”

Section: Heterocycles Originating From Acetylene-based Reactionsmentioning

confidence: 99%

Acetylenes in the Superbase-Promoted Assembly of Carbocycles and Heterocycles

Трофимов

Schmidt

2018

Acc. Chem. Res.

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In this Account, we briefly discuss the recently discovered and rapidly developing superbase-promoted self-organization reactions of several equivalents of acetylenes and ketones to afford complex compounds that represent promising synthetic building blocks common in natural products. Notably, acetylenes play a special role in these reactions because of their dual (acting as an electrophile and a nucleophile) and flexible reactivity. These unique properties of acetylenes are elegantly expressed in superbasic media, where acetylenes are more deprotonated and their electrophilicity increases as a result of complexation with alkali metal cations, with simultaneous enhancement of the nucleophilic reactants due to desolvation. Under these conditions, acetylenes behave as a driving and organizing force toward other reactants. Various combinations of nucleophilic addition to the triple bond and acetylene deprotonation in the presence of other reactants with dual reactivity (e.g., ketones) enables the self-organization of complex molecular architectures that are inaccessible by conventional reactions. Herein we analyze recent achievements in this area concerning the reactions of acetylenes with ketones in superbasic KOH/DMSO-type systems that selectively afford synthetically and pharmaceutically valuable carbo- and heterocycles. Most of the reactions are triggered by the nucleophilic addition of deprotonated ketones (enolate anions) to acetylenes (superbase-catalyzed C-vinylation of ketones with acetylenes, which was recently introduced by our group into a toolkit of organic chemistry). The β,γ-ethylenic ketones thus formed can then take part in cascade processes with ketones and acetylenes to afford either carbocycles (e.g., hexahydroazulenones, acyl terphenyls, functionalized and cyclopentenols) or heterocycles (e.g., furans, benzoxepines, dioxabicyclo[3.2.1]octanes, and dioxadispiro[5.1.5.2]pentadecanes), depending on the structure of the reactants and the reaction conditions. Most of these compounds are selectively built from several equivalents of ketones and acetylenes in different combinations, and despite the presence of two or more asymmetric carbons in the products, they are generated as single diastereomers. When other nucleophiles (hydroxylamine, hydrazines, guanidine, and oximes) and ketones are involved in these self-organization processes, the intermediate β,γ-ethylenic ketones allow the formation of diverse heterocyclic systems (pyrroles, isoxazolines, pyrazolines, aminopyrimidines, and azabicyclo[3.1.0]hexanes). The discovered unique chemical transformations do not require transition metal catalysts and proceed under mild and operationally simple conditions. Most of these syntheses involve cascade addition reactions and therefore represent pot-, atom-, step-, and energy-saving processes that meet the requirements of green chemistry. The significance of the approach discussed herein is that it represents a viable alternative to existing classic and modern transition-metal-based catalytic syntheses of some...

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Section: Heterocycles Originating From Acetylene-based Reactionsmentioning

confidence: 99%

Acetylenes in the Superbase-Promoted Assembly of Carbocycles and Heterocycles

Трофимов

Schmidt

2018

Acc. Chem. Res.

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“…Nowadays, the recently discovered base-catalyzed addition of ketones to alkynes to afford β,γ-ethylenic ketones has been successfully employed as the intermediate step for an efficient one-pot synthesis of 2-isoxazolines, 2-pyrazolines and 1-formyl-2-pyrazolines, benzoxepines, 2,5-diaryl furans, , and acylated terphenyls …”

Section: Results and Discussionmentioning

confidence: 99%

A One-Pot Synthesis of 2-Aminopyrimidines from Ketones, Arylacetylenes, and Guanidine

et al. 2016

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The three-component reaction of ketones, arylacetylenes, and guanidine catalyzed by the KOBu/DMSO system leads to 2-aminopyrimidines in up to 80% yield. Depending on structure of the starting ketones, the aromatization of intermediate dihydropyrimidines occurs either with loss of hydrogen molecules or methylbenzenes. The latter process takes place in the ketones, in which one of the substituents is not a methyl group. The reaction conditions are tolerable for dialkyl-, aryl(hetaryl) alkyl-, and cycloalkyl ketones.

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“…Oxidative cyclizations mediated by high-valent metals such as Cu(II) − and Ce(IV), − which proceed via a free-radical pathway, have received much attention in organic synthesis. Typically, enolic or enamic substrates 1 are initially oxidized by the high-valent metal to form carbon-centered radicals 2 .…”

Section: Introductionmentioning

confidence: 93%

Synthesis of Spiro-lactams and Polysubstituted Pyrroles via Ceric Ammonium Nitrate-Mediated Oxidative Cyclization of N-Furan-2-ylmethyl-β-Enaminones

Peng

Wang

et al. 2016

J. Org. Chem.

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Spiro-lactams and polysubstituted pyrroles were synthesized by reactions of furfurylamines with ynones followed by oxidation. Specifically, the protocol involved in situ generation of N-furan-2-ylmethyl-β-enaminones and their subsequent oxidation by ceric ammonium nitrate (6 equiv for spiro-lactam formation, 3 equiv for pyrrole formation). This useful dearomatizing oxidation, which likely proceeds via a free-radical pathway, can be expected to extend the synthetic applications of furan and pyrrole derivatives.

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A sequential synthesis of substituted furans from aryl alkynes and ketones involving a cerium(IV) ammonium nitrate (CAN)-mediated oxidative cyclization

Cited by 17 publications

References 37 publications

Acetylenes in the Superbase-Promoted Assembly of Carbocycles and Heterocycles

Acetylenes in the Superbase-Promoted Assembly of Carbocycles and Heterocycles

A One-Pot Synthesis of 2-Aminopyrimidines from Ketones, Arylacetylenes, and Guanidine

Synthesis of Spiro-lactams and Polysubstituted Pyrroles via Ceric Ammonium Nitrate-Mediated Oxidative Cyclization of N-Furan-2-ylmethyl-β-Enaminones

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