Theoretical Studies on Pentadienyl Cation Electrocyclizations

Tantillo, Dean J.

doi:10.2174/138527210793563297

Cited by 50 publications

(28 citation statements)

References 32 publications

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“…Chiral oxazolidinones (Evans’ oxazolidinones) are widely utilized as α‐substituents to control the stereo‐ and regioselectivity of the interrupted Nazarov cyclizations . Kerr et al .…”

Section: Interrupted Nazarov‐type Reactionmentioning

confidence: 99%

Recent Advances in the Interrupted Nazarov Reaction

Yadykov

Ширинян

2019

Adv Synth Catal

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In recent decades there have been significant improvements in the efficiency of synthesis as a result of considerable progress in tandem reactions, cascade transformations and related one‐pot processes. These methodologies are less time‐consuming, more cost‐effective, and produce less waste compared to the classical stepwise protocols. The Nazarov cyclization is an important and versatile method for the synthesis of five‐membered carbocycles which are found in many natural compounds and functional molecules. Current activities in the field of the Nazarov reaction are focused on development of better catalysts, asymmetric options and increasing the efficiency of synthesis. This transformation is suitable for applying to an intensified step‐economy in interrupted versions and one‐pot protocols. Interrupted Nazarov reactions in particular take advantage of the stereospecific nature of the electrocyclization. The universality of these reactions has facilitated an access to a plethora of complex small molecules of high medicinal relevance. In this review, we present a comprehensive summary of recent advances in the interrupted Nazarov‐type cyclization, and classify these reactions according to the structure of the substrate or the reaction mechanism. This is the first review that presents a survey on various types of interrupted Nazarov cyclization and deals with the recent advances, especially using tandem/domino or one‐pot reaction strategies and covers the literature from 2009 to 2019.

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Section: Interrupted Nazarov‐type Reactionmentioning

confidence: 99%

Recent Advances in the Interrupted Nazarov Reaction

Yadykov

Ширинян

2019

Adv Synth Catal

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“…The lack of success in developing an imino-Nazarov cyclization stems from the inherent challenge associated with higher stability of the pentadienyl cation, relative to the corresponding cyclic allyl cation, owing to stabilization by a nitrogen atom. [14] Hydrolysis of II following an imino-Nazarov reaction would then furnish the 4-aminocyclopentenone product 3. [7] The work of Hsung and co-workers on gold-catalyzed cyclization of allenamides demonstrated that diminishing nitrogen stabilization through incorporation of an electron-withdrawing tosyl group proved to be an effective solution to drive the electrocyclization forward.…”

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confidence: 99%

“…[7] The work of Hsung and co-workers on gold-catalyzed cyclization of allenamides demonstrated that diminishing nitrogen stabilization through incorporation of an electron-withdrawing tosyl group proved to be an effective solution to drive the electrocyclization forward. [14] Hydrolysis of II following an imino-Nazarov reaction would then furnish the 4-aminocyclopentenone product 3. [9] Our recent interest in the synthesis of cyclopentanoid compounds [10] prompted us to investigate the possibility of a diene iminium ion, of the type shown in Scheme 1, to undergo an imino-Nazarov cyclization, and to explore the related interrupted process.…”

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confidence: 99%

“…[9] Our recent interest in the synthesis of cyclopentanoid compounds [10] prompted us to investigate the possibility of a diene iminium ion, of the type shown in Scheme 1, to undergo an imino-Nazarov cyclization, and to explore the related interrupted process. [14] Hydrolysis of II following an imino-Nazarov reaction would then furnish the 4-aminocyclopentenone product 3. [12] In addition, the iminium ion I is expected to serve as an excellent substrate for the imino-Nazarov cyclization because of the polarized nature of the conjugated p system.…”

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Interrupted Imino‐Nazarov Cyclization of 1‐Aminopentadienyl Cation and Related Cascade Process

et al. 2014

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Facile 4π conrotatory imino-Nazarov cyclization of a 1-aminopentadienyl cation generated from condensation an aldehyde and secondary aniline in the presence of a catalytic amount of a Lewis acid has been developed. Silver(I)-catalyzed intramolecular arene trapping of the resulting cyclic oxyallyl cation leads to formation of tricyclic indoline-fused cyclopentanone. The use of lanthanide salts allows transformation after the initial trapping to afford tetrahydroquinoline-fused cyclopentenone in a concise manner.

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“…The requirement of high acid concentration is consistent with the cyclization of a diprotonated intermediate of the type that West and coworkers have postulated in certain Nazarov cyclizations. [14],[15] …”

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Diastereospecific Nazarov Cyclization of Fully Substituted Dienones: Generation of Vicinal All‐Carbon‐Atom Quaternary Stereocenters

et al. 2013

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The joining of two carbon atoms through a σ bond so as to form vicinal all-carbon atom quaternary centers remains a difficult challenge in organic synthesis. [1] An effective strategy to address the problem is to exploit an orbital symmetry controlled process. [2] We describe herein a diastereospecific Nazarov cyclization [3] that leads to cyclopentenones bearing adjacent all-carbon atom quaternary centers.We are aware of only the three examples of Nazarov cyclizations that lead to two contiguous all-carbon atom quaternary stereocenters during the ring forming step that are shown in Scheme 1. The first two examples in Scheme 1 describe Harding and coworkers' efforts that culminated in the total synthesis of (d,l)-trichodiene. [4] Reaction conditions in both cases were harsh but the yield of cyclic products 2 and 4 that lack sensitive functionality was high. Both reactions were diastereospecific, with the C3a,C3b relative stereochemistry (see compound 2) determined by the conrotation that is required by the selection rule governing the thermal 4π electron process. The third example in Scheme 1 is the oxidative Nazarov cyclization of allenyl ether 5 that was reported by Frontier and coworkers in 2011. [5] The oxyallyl zwitterion that forms spontaneously from the allene oxide following treatment of 5 with dimethyldioxirane (DMDO) underwent stereospecific cyclization to 6 in moderate yield. The zwitterion intermediate is strongly polarized, hence the mild reaction conditions.

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Theoretical Studies on Pentadienyl Cation Electrocyclizations

Cited by 50 publications

References 32 publications

Recent Advances in the Interrupted Nazarov Reaction

Recent Advances in the Interrupted Nazarov Reaction

Interrupted Imino‐Nazarov Cyclization of 1‐Aminopentadienyl Cation and Related Cascade Process

Diastereospecific Nazarov Cyclization of Fully Substituted Dienones: Generation of Vicinal All‐Carbon‐Atom Quaternary Stereocenters

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