Unusual Formation of Cyclopenta[<i>b</i>]indoles from 3-Indolylmethanols and Alkynes

Gandhi, Soniya; Baire, Beeraiah

doi:10.1021/acs.joc.8b03027

Cited by 23 publications

(7 citation statements)

References 92 publications

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“…Firstly, the alcohols 64 were activated by HNTf 2 to form o ‐QM species A , which then underwent the intermolecular Michael addition with thioalkynes 63 to afford the sulfonium intermediates B . The four‐membered spiro intermediates C were then obtained from B through [2+2] cycloaddition [73] which was similar to Baire's formal [3+2] annulation involving the generation of spirocyclobutene intermediates [74] . The ring opening of C followed by intramolecular Michael addition resulted in the desired 2 H ‐chromenes 65 (Scheme 20).…”

Section: Formations Of Fused‐cycles From Thioalkynesmentioning

confidence: 99%

“…[70] membered spiro intermediates C were then obtained from B through [2 + 2] cycloaddition [73] which was similar to Baire's formal [3 + 2] annulation involving the generation of spirocyclobutene intermediates. [74] The ring opening of C followed by intramolecular Michael addition resulted in the desired 2Hchromenes 65 (Scheme 20). This HNTf 2 catalyzed annulation, giving a practical and facile preparation of substituted 2Hchromenes in high yields with wide functional group tolerance under mild reaction, was the first case of formal [4 + 2] annulation of alkynes with o-hydroxybenzyl alcohols.…”

Section: Formation Of Benzo-cycles From Thioalkynesmentioning

confidence: 99%

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Thioalkynes in Ring Forming Reactions

Peng,

Yuan,

Tang

et al. 2023

The Chemical Record

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Organic cycles play an important role in chemistry, pharmacology and material science for their unique properties. Construction of organic cycles from thioalkynes attracted increasing attention due to the facile access of thioalkynes. 2H‐Azirines were synthesized successfully from thioalkynyl oxime ethers. Cyclobutanes were formed through chiral titanium catalyzed cycloaddition of thioalkynes. Cyclopentenes were afforded by annulation of thioalkynes. Thioalkynes could be also applied to synthesize thiophenes, oxazoles, benzo[b]thiophenes, 2H‐chromenes, 2‐phenylbenzothiazoles, diazacyclobutene, etc. In this review, construction of organic cycles from thioalkynes were highlighted. Firstly, the property and application of organic cyclic compounds were simply introduced. After presenting the general methods to access organic cycles, applications of thioalkynes as synthons to prepare organic cycles were classified and presented in detail. Based on different kinds of organic cycles obtained from thioalkynes, organic reactions for synthesis of three‐, four‐, five‐, six‐membered as well as fused cycles would be summarized and the plausible reaction mechanisms could be presented if available.

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Section: Formations Of Fused‐cycles From Thioalkynesmentioning

confidence: 99%

Section: Formation Of Benzo-cycles From Thioalkynesmentioning

confidence: 99%

Thioalkynes in Ring Forming Reactions

Peng,

Yuan,

Tang

et al. 2023

The Chemical Record

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“…In 2019, our research group also discovered and developed a FeCl 3 -catalysed, an unprecedented formal [3 + 2] annulation of indole-3-carbinols 72 with alkynes 73 via a skeletal rearrangement to synthesize rearranged cyclopenta[b]indole frameworks 74 (Scheme 23). [25] This reaction had shown a very broad substrate scope for both alkynes as well as indole-3carbinols.…”

Section: Cyclizative Coupling Strategiesmentioning

confidence: 99%

Fe‐Catalysed Coupling Reactions Between Alkynes and Alcohols

Khan

Baire

2021

The Chemical Record

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In this review, we discussed about the synthetic developments in the field of Fecatalysis for the formation of -bonds through the coupling of alkynes and alcohols, for the period of 13 years (2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019)(2020). These strategies fulfil important Green Chemistry principles, as they are highly atom economic (up to 100 %), no toxic by-products (only water), employs highly abundant and low toxic alcohols (no need for any pre-functionalization hence step economy) and cheaper Fe-catalysts. Having these advantages, one can predict that in the coming years a large number of fascinating new iron-catalyzed reactions will be developed for the organic synthesis. We hope that this review article will be highly useful for the synthetic community to design and develop new Fe-catalyzed coupling reactions and keeps the content in the right prospect.

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“…As a result, the construction of such indole-containing scaffolds has remained a long-standing goal in the chemistry community [14][15][16][17][18][19][20] and many synthetic approaches have been developed for the synthesis of these important structural units [21][22][23][24][25][26][27][28][29] . Among these approaches, the Nazarov-type cyclization [30][31][32][33][34][35][36][37] for the construction of 1, 2, 3, 4-tetrahydrocyclopenta [b]indole scaffolds is undoubtedly one of the most stepeconomical and efficient methods [38][39][40][41][42][43][44][45][46][47] .…”

Section: Introductionmentioning

confidence: 99%

Organocatalytic Nazarov-type cyclization of 3-alkynyl-2-indolylmethanols: construction of axially chiral cyclopenta[b]indole scaffolds

Wu¹,

Yan²,

Jiang³

et al. 2023

Chem Synth

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In recent years, it has become an urgent task to design new types of indole-based platform molecules for Nazarov-type cyclizations and develop organocatalytic Nazarov-type cyclizations for synthesizing indole derivatives. To fulfill this task, in this work, by changing the alkynyl terminal substituent from t-Bu to an aryl group, the reactivity of 3-alkynyl-2-indolylmethanols is modulated and the new platform molecules serve as competent substrates for Brønsted acid-catalyzed Nazarov-type cyclization. Based on this new reactivity, the first organocatalytic Nazarov-type cyclization of aryl-substituted 3-alkynyl-2-indolylmethanols with 2-naphthols is accomplished, leading to the efficient construction of a new class of axially chiral 3, 4-dihydrocyclopenta[b]indole scaffolds. This preliminary investigation of organocatalytic asymmetric Nazarov-type cyclization provides an optional strategy for the atroposelective construction of this new class of axially chiral cyclopenta[b]indole scaffolds. In addition, the first preparation of axially chiral 3, 4-dihydrocyclopenta[b]indole with optical purity is established through chiral resolution, which could serve as a complementary method to catalytic asymmetric approaches.

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Unusual Formation of Cyclopenta[b]indoles from 3-Indolylmethanols and Alkynes

Cited by 23 publications

References 92 publications

Thioalkynes in Ring Forming Reactions

Thioalkynes in Ring Forming Reactions

Fe‐Catalysed Coupling Reactions Between Alkynes and Alcohols

Organocatalytic Nazarov-type cyclization of 3-alkynyl-2-indolylmethanols: construction of axially chiral cyclopenta[b]indole scaffolds

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