Nazarov Reactions Intercepted by (4 + 3) Cycloadditions with Oxygen-Substituted Dienes

LeFort, François M.; Mishra, Vinayak; Dexter, Graham D.; Morgan, Timothy D. R.; Burnell, D. Jean

doi:10.1021/acs.joc.5b00914

Cited by 23 publications

(21 citation statements)

References 36 publications

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“…We propose that the mechanism involves alkyl migration of the oxyallyl cation intermediate to form a stabilized benzylic cation, followed by 1,2‐phenyl migration. This suggests that alternate pathways such as rearrangements, or oxyallyl cation trapping,, by excess diene or side products can account for the lower yield of product 6 , although we were unable to observe or isolate these products. We also looked at using the more Lewis acidic boron trichloride as a catalyst in an attempt to optimize the yield (Scheme b).…”

Section: Methodsmentioning

confidence: 76%

Multicomponent Double Diels–Alder/Nazarov Tandem Cyclization of Symmetric Cross‐Conjugated Diynones to Generate [6‐5‐6] Tricyclic Products

Carmichael

Chalifoux

2016

Chemistry A European J

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The construction of complex polycyclic terpenoid products in an efficient and step-economical manner using multicomponent and tandem processes is highly valuable. Herein, we report a tandem cyclization sequence that initiates with a multicomponent double Diels-Alder reaction of cross-conjugated diynones, followed by a Nazarov cyclization to efficiently produce [6-5-6] tricyclic products with excellent regio- and diastereoselectivity. This methodology generates five new carbon-carbon bonds, three rings, quaternary or vicinal quaternary carbons, and stereogenic centers in a one-pot reaction.

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Section: Methodsmentioning

confidence: 76%

Multicomponent Double Diels–Alder/Nazarov Tandem Cyclization of Symmetric Cross‐Conjugated Diynones to Generate [6‐5‐6] Tricyclic Products

Carmichael

Chalifoux

2016

Chemistry A European J

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“…In the case of unsymmetrical diene nucleophiles, e.g., 1,3‐pentadiene, the electron‐donating terminal group is attacked by the allenyl group giving products 109a, b, d . Subsequent studies using quantum‐chemical calculations showed that the [3+4] cycloaddition can proceed according to both a concerted or a sequential mechanism …”

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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“…Burnell and colleagues reported a different type of tandem reaction, in which Nazarov cyclization intermediate 27# , derived from the allenyl vinyl ketone 26 , was trapped by the activated diene 28 via the [4 + 3] cycloaddition and subsequent rearrangement of 29a to afford the cyclopentene derivative 30 in excellent yield (Figure ) 13…”

Section: Recent Trends In Nazarov Cyclizationmentioning

confidence: 99%

Recent Progress on Nazarov Cyclizations: The Use of Iron Salts as Catalysts in Ionic Liquid Solvent Systems

Itoh

Nokami

Kawatsura

2016

The Chemical Record

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Nazarov cyclization is an important and versatile method for the synthesis of five-membered carbocycles, and extensive studies have been conducted to optimize the reaction. Among recent studies, several trends are recognized. One is the combination of different reactions with Nazarov cyclization in a one-pot reaction system which enables the preparation of unique cyclization products. The second is the use of a transition-metal catalyst, though Lewis or Brønsted acids have generally been used for the reaction. The third is the realization of the asymmetric Nazarov cyclization. The fourth is the base-catalyzed Nazarov cyclization. Furthermore, several useful protocols for realizing Nazarov cyclization have also been developed. The recent progress on Nazarov cyclizations is summarized in Section 2. Section 3 is our chronicle in this field. We focused on the use of iron as the catalyst in Nazarov cyclizations and ionic liquids as solvents: Nazarov cyclization of thiophene derivatives using FeCl3 as the catalyst was accomplished and we succeeded in demonstrating the first example of an iron-catalyzed asymmetric Nazarov reaction. We next established Nazarov cyclization of pyrrole or indole derivatives using Fe(ClO4 )3 ·Al2 O3 as the catalyst with high trans selectivities in excellent yields. Since the cyclized product was reacted with a vinyl ketone in the presence of the same iron salt, the system allowed realization of the sequential type of Nazarov/Michael reaction of pyrrole derivatives. Furthermore, we demonstrated the recyclable use of the iron catalyst and obtained the desired Nazarov/Michael reaction products in good yields for five repetitions of the reactions without any addition of the catalyst using an ionic liquid, [bmim][NTf2 ], as the solvent. We expect that the iron-catalyzed Nazarov cyclization, in particular, in an ionic liquid solvent might become a useful method to synthesize functional molecules that include cycloalkene moieties.

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Nazarov Reactions Intercepted by (4 + 3) Cycloadditions with Oxygen-Substituted Dienes

Cited by 23 publications

References 36 publications

Multicomponent Double Diels–Alder/Nazarov Tandem Cyclization of Symmetric Cross‐Conjugated Diynones to Generate [6‐5‐6] Tricyclic Products

Multicomponent Double Diels–Alder/Nazarov Tandem Cyclization of Symmetric Cross‐Conjugated Diynones to Generate [6‐5‐6] Tricyclic Products

Recent Advances in the Interrupted Nazarov Reaction

Recent Progress on Nazarov Cyclizations: The Use of Iron Salts as Catalysts in Ionic Liquid Solvent Systems

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