C3‐Alkenylation between Pyrroles and Aldehydes Mediated by a Brønsted Acid and a Brønsted Base

Sahu, Samrat; Roy, Avijit; Gorai, Mahadeb; Guria, Sudip; Maji, Modhu Sudan

doi:10.1002/ejoc.201901228

Cited by 7 publications

(4 citation statements)

References 54 publications

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“…[1] In 2019, Sahu et al performed one-pot two fold C3-alkenylation between pyrroles and aldehydes by using Brønsted acid and base to get indole-based molecules 61 a-b through Cadogan cyclization as the final step (Scheme 14). [39] In the same year, Moreno Cury and colleagues synthesized a novel series of potent 2-carboxy indole derivatives and elucidated their mechanism of action along with both in vitro and in vivo anti-leukemia potency. [40] The synthesis of these indole-based molecules (63, 65, 67) interestingly involved two Heck-Matsuda arylations to get disubstituted acrylates (62, 64, 66) followed by Cadogan-Sundberg reaction to afford the desired molecules (Scheme 15).…”

Section: Construction Of Indole Skeletonmentioning

confidence: 99%

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A Minireview on the Scope of Cadogan Cyclization Reactions Leading to Diverse Azaheterocycles

Kaur

Kumar

2022

Asian J Org Chem

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From the last two decades, Cadogan cyclization reaction is considered as one of the best routes for the preparation of various azaheterocycles comprising carbazoles, indoles, coumarins, carbolines, pyrazoloquinoxalines, S,N‐heterotetracenes from the nitro‐based substrates by using a variety of tetravalent phosphorus‐based reagents. To date the majority of Cadogan reactions are found to be intramolecular reactions, however, interestingly, a case of intermolecular Cadogan reaction is also reported, resulting in the widening of the reaction scope for futuristic perspectives. We report the Cadogan cyclization reactions for the synthesis of azaheterocycles from 2018 to present according to multiple classes of chemical frameworks including its scope (FDA approved drugs), along with the possibilities and mechanistic developments for unexpected products.

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Section: Construction Of Indole Skeletonmentioning

confidence: 99%

“…performed one‐pot two fold C3‐alkenylation between pyrroles and aldehydes by using Brønsted acid and base to get indole‐based molecules 61 a – b through Cadogan cyclization as the final step (Scheme 14). [39] …”

Section: Synthesis Of Chemical Frameworkmentioning

confidence: 99%

A Minireview on the Scope of Cadogan Cyclization Reactions Leading to Diverse Azaheterocycles

Kaur

Kumar

2022

Asian J Org Chem

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“…A one‐pot two‐overlap alkenylation system is likewise created for additional downstream adjustments (Scheme 133). [150] …”

Section: C−h Functionalization Of Pyrrolesmentioning

confidence: 99%

Recent Advances in Functionalization of Pyrroles and their Translational Potential

Hunjan

Panday

Gupta

et al. 2021

The Chemical Record

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Among the known aromatic nitrogen heterocycles, pyrrole represents a privileged aromatic heterocycle ranging its occurrence in the key component of “pigments of life” to biologically active natural products to active pharmaceuticals. Pyrrole being an electron‐rich heteroaromatic compound, its predominant functionalization is legendary to aromatic electrophilic substitution reactions. Although a few excellent reviews on the functionalization of pyrroles including the reports by Baltazzi in 1963, Casiraghi and Rassu in 1995, and Banwell in 2006 are available, they are fragmentary and over fifteen years old, and do not cover the modern aspects of catalysis. A review covering a comprehensive package of direct functionalization on pyrroles via catalytic and non‐catalytic methods including their translational potential is described. Subsequent to statutory yet concise introduction, the classical functionalization on pyrroles using Lewis acids largely following an ionic mechanism is discussed. The subsequent discussion follows the various metal‐catalyzed C−H functionalization on pyrroles, which are otherwise difficult to implement by Lewis acids. A major emphasize is given on the radical based pyrrole functionalization under metal‐free oxidative conditions, which is otherwise poorly highlighted in the literature. Towards the end, the current development of pyrrole functionalization under photocatalyzed and electrochemical conditions is appended. Only a selected examples of substrates and important mechanisms are discussed for different methods highlighting their scopes and limitations. The aromatic nucleophillic substitution on pyrroles (being an electron‐rich heterocycle) happened to be the subject of recent investigations, which has also been covered accentuating their underlying conceptual development. Despite great achievements over the past several years in these areas, many challenges and problems are yet to be solved, which are all discussed in summary and outlook.

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“…In our continuous efforts to use in situ generated indolyl cations for the synthesis of functionalized indoles, we envisioned that Brønsted acid-catalyzed pinacol-type rearrangement can also be achieved by employing unprotected indoles and α-hydroxy aldehydes as coupling partners to accomplish diversely substituted α-(3-indolyl) ketones . According to our hypothesis, in the presence of a Brønsted acid catalyst, first, indole 1 would react with α-hydroxy aldehyde 2 to generate indolyl diol intermediate A , which presumably would undergo dehydration to form the vinylogous iminium intermediate B .…”

Section: Introductionmentioning

confidence: 99%

Brønsted Acid-Catalyzed Tandem Pinacol-Type Rearrangement for the Synthesis of α-(3-Indolyl) Ketones by Using α-Hydroxy Aldehydes

2019

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A Brønsted acid-catalyzed pinacol-type rearrangement pathway is reported here to synthesize various substituted α-(3-indolyl) ketones by employing unprotected indoles and α-hydroxy aldehydes as coupling partners. Utilization of economic and readily available Brønsted acid catalyst and use of simple starting precursors exemplify the economic viability of this method. Under this developed protocol, selective migration of aryl over alkyl or a second aryl group is observed depending upon the migratory aptitude of the substituents. Applicability of this method was further demonstrated by synthesizing highly substituted carbazoles through a simple extension of this method to one-pot cascade annulation strategy.

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C3‐Alkenylation between Pyrroles and Aldehydes Mediated by a Brønsted Acid and a Brønsted Base

Cited by 7 publications

References 54 publications

A Minireview on the Scope of Cadogan Cyclization Reactions Leading to Diverse Azaheterocycles

A Minireview on the Scope of Cadogan Cyclization Reactions Leading to Diverse Azaheterocycles

Recent Advances in Functionalization of Pyrroles and their Translational Potential

Brønsted Acid-Catalyzed Tandem Pinacol-Type Rearrangement for the Synthesis of α-(3-Indolyl) Ketones by Using α-Hydroxy Aldehydes

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