Metallfreie Tandem‐Umlagerung/Lactonisierung: Zugang zu 3,3‐disubstituierten Benzofuran‐2‐(3<i>H</i>)‐onen

Santi, Micol; Ould, Darren M. C.; Wenz, Jan; Soltani, Yashar; Melen, Rebecca L.; Wirth, Thomas

doi:10.1002/ange.201902985

Cited by 17 publications

(2 citation statements)

References 54 publications

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“…We have also investigated the stoichiometric addition of Lewis acidic boranes BAr 3 with α-diazo carbonyl compounds (1:1 ratio) in the aryl transfer reaction (Scheme 4 ). 31 It was found by X-ray diffraction analysis that the triarylborane coordinated to the diazo compound through ester O→B adduct formation rather than N→B formation as observed by Stephan and co-workers for Ph 2 CN 2 . 26 Subsequently, at room temperature or higher, N 2 release rapidly occurred and the aryl group migrated from BAr 3 to the carbene carbon center yielding a similar boron enolate to that observed by Stephan and co-workers (Scheme 3 ).…”

Section: Diazo Activation Using Stoichiometric Boranesmentioning

confidence: 88%

“…This was found both experimentally and computationally (Figure 1 ). 31 34 35 By DFT studies the C–N bond in the boron-coordinated diazo ester is longer and weaker (1.334 Å) than in the free uncoordinated diazo ester (1.318 Å). 14 In addition, a shortening of the C–C bond length from 1.470 Å to 1.436 Å was also observed for the O→B adduct.…”

Section: Diazo Activation Using Catalytic B(c 6 F ...mentioning

confidence: 99%

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Activation of Diazo Compounds by Fluorinated Triarylborane Catalysts

Pramanik

Melen

2023

Synthesis

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The diverse applicability of diazo compounds as versatile reagents has enlarged the chemical toolbox in organic synthesis. Over the past few decades, transition metal-catalyzed diazo compound activation has ignited the classical synthetic methodology via utilizing highly reactive metal carbenoid species. Many reviews have also appeared in the literature which discloses the advantage and disadvantages of metal-catalyzed activation of the diazo compound. Recently, tris(pentafluorophenyl) borane-mediated diazo activation reactions have reconciled this research area due to the potential for mild, environmentally-friendly, metal-free, non-toxic reaction conditions, and the diverse reactivity patterns of boranes towards diazo compounds. In this review, we have discussed the reactivity of the boron-diazo precursor adduct with compounds using catalytic and stoichiometric halogenated triarylboranes and, the mechanism of N2 release from the diazo reagent. This generates the reactive carbene species as a key intermediate which can further be exploited for O−H, N−H, S‒H, and C−H insertions, azide insertion, carbonate transfer, C‒C and C=C bond forming reactions, [2+2] or [2+4] cascade cyclization reactions, annulation reactions, etc. This review is classified by the following themes: 1. Introduction 2. Diazo Activation Using Stoichiometric Boranes 3. Diazo Activation Using Catalytic B(C6F5)3 4. B(C6F5)3 Catalyzed Diazo Activation Reactions 5. Conclusions

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Section: Diazo Activation Using Stoichiometric Boranesmentioning

confidence: 88%

Section: Diazo Activation Using Catalytic B(c 6 F ...mentioning

confidence: 99%

Activation of Diazo Compounds by Fluorinated Triarylborane Catalysts

Pramanik

Melen

2023

Synthesis

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Borane Catalyzed Selective Diazo Cross‐Coupling Towards Pyrazoles

et al. 2021

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Decomposition of donor‐acceptor diazo compounds leads to the formation of reactive carbene intermediates. These can undergo a wide variety of carbene transfer reactions to yield synthetically useful products. Herein, we report a selective borane catalyzed cyclization reaction from the combination of two different diazo compounds to afford N‐substituted pyrazoles. The selective decomposition of the more reactive α‐aryl α‐diazoester and subsequent reaction with a vinyl diazoacetate produces N‐alkylated pyrazoles in a regioselective manner. Catalytic amounts of tris(pentafluorophenyl)borane (10 mol%) were employed to afford the pyrazole products (36 examples) in yields from 59 to 80%. Extensive DFT studies have been undertaken to interpret the mechanism for this reaction which was found to go through two tandem catalytic cycles, both catalyzed by B(C6F5)3.

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Rapid and Efficient Construction of Indolizino[3,4,5‐ab]isoindole Skeletons by a Rhodium‐Catalyzed Tandem Reaction

Liu

Sun

et al. 2019

Asian J Org Chem

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A facile rhodium-catalyzed tandem reaction of two molecules of acrylates with two molecules of 2phenylpyridines involving sequential CÀ H activation, Michael addition, [12 + 2] cycloaddition and oxidative aromatization has been described. A series of indolizino [3,4,5-ab] isoindole compounds were efficiently afforded in good yields by the formation of two CÀ C bonds, two C=C bonds and one CÀ N bond.

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Metallfreie Tandem‐Umlagerung/Lactonisierung: Zugang zu 3,3‐disubstituierten Benzofuran‐2‐(3H)‐onen

Cited by 17 publications

References 54 publications

Activation of Diazo Compounds by Fluorinated Triarylborane Catalysts

Activation of Diazo Compounds by Fluorinated Triarylborane Catalysts

Borane Catalyzed Selective Diazo Cross‐Coupling Towards Pyrazoles

Rapid and Efficient Construction of Indolizino[3,4,5‐ab]isoindole Skeletons by a Rhodium‐Catalyzed Tandem Reaction

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