An Interrupted Vinylogous Iso-Nazarov Reaction: Cycloisomerization of Conjugated Trienones to Cyclopenta[<i>b</i>]furan Derivatives

Riveira, Martín J.; Mischne, Mirta P.

doi:10.1021/jo501453b

Cited by 27 publications

(17 citation statements)

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“…Whereas this rearrangement was attributed to acid traces present within the deuterated solvent, the cationic Nazarov pathway was later cleanly supported by the finding that stable trienediketones such as 176 (R = H) rearranged to their polycyclic isomers 177 upon Lewis or Brønsted acid activation (Scheme 35C). 69 Since we later found that the process could be rendered possible also under neutral conditions (refluxing toluene) we departed from the classical cationic point of view and a pericyclic cascade was elaborated and supported computationally. 75 This proposal involves an initial isomerization via well-known oxa-6π processes to deliver a We were somehow pretty sure that, based on the ease with which these polyenes undergo neat and precise polycylizations, this cascade had to be traced in Nature.…”

Section: Examples 25-82% Yieldmentioning

confidence: 99%

The iso-Nazarov reaction

2017

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The construction of five-membered rings is essential in organic chemistry. In this context, pentannulation reactions that provide a straightforward access to cyclopentenones are of particular interest, as these structures are not only embedded in important molecules such as some prostaglandins, but also serve as versatile building blocks in organic synthesis. This review documents the acid-promoted cycloisomerization of conjugated dienals and linearly-conjugated dienones for the construction of cyclopentenones, a transformation that has been largely eclipsed by the well-known Nazarov reaction, i.e. the acid-promoted cycloisomerization of cross-conjugated ketones.

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Section: Examples 25-82% Yieldmentioning

confidence: 99%

The iso-Nazarov reaction

2017

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“…Mischne and Riveira came up with a plan to accomplish the cyclopentannulation of the linearly conjugated 1,3-dicarbonyl substrate 234 (Scheme 34). 62 An iron (III)mediated catalysis provides a corresponding species 235, which readily isomerises to a pentadienyl cation 236. Then, 4π electrocyclisation furnishes a cyclopentenyl cation 237 that may achieve intramolecular stabilisation by a through-space interaction with the π electrons of the enoyl moiety.…”

Section: π Electrocyclisation-cyclisation Methodologymentioning

confidence: 99%

“…affords a rearranged cyclopenta [b]furan product 240 (Scheme 34). 62 This suggests that the reac-tion has kinetic and thermodynamic preferences which can lead to two different types of cyclopenta [b]furan derivatives.…”

Section: π Electrocyclisation-cyclisation Methodologymentioning

confidence: 99%

4π electrocyclisation in domino processes: contemporary trends and synthetic applications towards natural products

Sheikh

2015

Org. Biomol. Chem.

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Recent most instructive and reliable literature reports which deal with domino processes involving conrotatory 4π electrocyclic reactions, along with a precise mechanistic insight and latest synthetic applications towards biologically active natural products are concisely reviewed. To inspire further research in this domain, a real insight into the overarching emerging themes and potential imminent prospects is also provided.

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“…A study of the iso ‐Nazarov cyclization of 2,4,6‐trienediones 126 has shown that the reaction leading to bicyclic compound 128 is reversible and that the latter exists in thermodynamic equilibrium with cyclopentenyl carbocation 127 (Scheme ) . This cation can also eliminate a proton in the presence of an excess of a Lewis acid to give cyclopentadiene 129 .…”

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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An Interrupted Vinylogous Iso-Nazarov Reaction: Cycloisomerization of Conjugated Trienones to Cyclopenta[b]furan Derivatives

Abstract: Iron(III) chloride-catalyzed cyclopentannulation of π-conjugated 1,3-dicarbonyl compounds is described. An interrupted vinylogous iso-Nazarov reaction of trienones was established in which cyclopenta[b]furan derivatives are obtained as single diastereomers.

Cited by 27 publications

References 50 publications

The iso-Nazarov reaction

The iso-Nazarov reaction

4π electrocyclisation in domino processes: contemporary trends and synthetic applications towards natural products

Recent Advances in the Interrupted Nazarov Reaction

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