Enantioselective 5-exo-Fluorocyclization of Ene-Oximes

Rouno, Taiki; Niwa, Tomoki; Nishibashi, Kousuke; Yamamoto, Nobuto; Egami, Hiromichi; Hamashima, Yoshitaka

doi:10.3390/molecules24193464

Cited by 26 publications

(15 citation statements)

References 45 publications

(50 reference statements)

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“…With β,γ‐unsaturated oximes, fluorinated isoxazolines were obtained via 5‐ exo ‐fluorocyclization with moderate efficiencies (Scheme 12). 26 These reactions were accompanied by side products arising from fluorocarbocation, implying the insufficient cyclizing ability of oxime. In addition, with the hydrogen‐bonding ability removed, O ‐methyl oxime ether was completely unreactive, which confirms the necessity of hydrogen‐bonding in the fluorination step.…”

Section: Electrophilic Halogenation With Chiral Anionic Phase‐transfe...mentioning

confidence: 99%

Enantioselective halogenation via asymmetric phase‐transfer catalysis

Lee

Chung

2022

Bulletin Korean Chem Soc

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The asymmetric phase‐transfer catalysis (PTC) is a flourishing field of contemporary synthetic organic chemistry, and this prominent methodology has been tremendously successful in enantioselective halogenations. Both electrophilic and nucleophilic reaction manifolds were enabled through the exploitation of highly ordered ion pairing and/or hydrogen‐bonding interactions around a carefully designed chiral phase‐transfer catalyst with an insoluble halogenating reagent as well as a suitable substrate. Fluorination has been the most fruitful, and encouraging results have also been documented with heavier halogens. This review surveys examples of various enantioselective halogenations via the asymmetric PTC from its beginning to prosperity over the past decade.

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Section: Electrophilic Halogenation With Chiral Anionic Phase‐transfe...mentioning

confidence: 99%

Enantioselective halogenation via asymmetric phase‐transfer catalysis

Lee

Chung

2022

Bulletin Korean Chem Soc

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“…Ene‐oximes 13 were also shown to be good substrates for fluorocyclization [62] . In the presence of C4 , Selectfluor and Na 3 PO 4 , they afforded chiral isoxazolidines 14 in moderate to good yields and high ees.…”

Section: Direct Fluorinationmentioning

confidence: 99%

“…Ene-oximes 13 were also shown to be good substrates for fluorocyclization. [62] In the presence of C4, Selectfluor and Na 3 PO 4 , they afforded chiral isoxazolidines 14 in moderate to good yields and high ees. 5-Exo-fluorocyclization was observed in this case, by Toste and coworkers, in the reaction of an amide bearing an unactivated allylic double bond, i. e. N-(2-methylallyl) benzamide, which led to isoxazolidine 4, albeit under more forcing conditions (60°C) (Figure 8).…”

Section: Cyclization Triggered By Fluorinationmentioning

confidence: 99%

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Recent Developments in Enantioselective Organocatalytic Cascade Reactions for the Construction of Halogenated Ring Systems

Phillips

Pombeiro

2021

Eur J Org Chem

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Chiral halogenated substances have many applications in pharmaceuticals, agrochemicals, and materials, such as polymers, liquid crystals and as intermediates in synthesis. The presence of a halogen atom in a molecule can have a large effect in its properties; for instance, halogens are used in drugs to improve lipophilicity, membrane permeability and absorption, and even the blood‐brain barrier permeability. As highlighted in this review, there are nowadays a range of highly selective, versatile halogenating reagents, electrophilic, nucleophilic or radical in nature, which operate under mild conditions, allowing late‐stage functionalization of complex molecules in cascade reactions. Recent developments in organocatalyst design revealed novel Cinchona alkaloids derivatives, chiral phosphoric acids, amines, phosphines and several bifunctional catalysts, mostly thiourea‐ or squaramide‐based, which introduced chirality, with high levels of enantio‐ and diastereoselection, in the formation of one or multiple chiral centers in a single synthetic operation, as shown. In this review we survey the literature published in this field from 2014 to 2020.

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“…Using the same dicarboxylic acid precatalysts 24a and more recently, Hamashima's group has developed two additional works. One of them is based on the development of an enantioselective 5‐ exo ‐fluorocyclization of ene‐oxime compounds [43] and the most recent one is an asymmetric dearomative fluorination of 2‐naphthols [44] . In all cases, the catalytic species is formed by a dicarboxylate dianion generated in situ by deprotonation of 24 and Selectfluor 1 , allowing the transfer of 1 from the solid phase to the liquid phase giving rise to a chiral Selectfluor species as described in Figure 5.…”

Section: Chiral Anionic Phase‐transfer Catalystsmentioning

confidence: 99%

Asymmetric Fluorination Reactions promoted by Chiral Hydrogen Bonding‐based Organocatalysts

et al. 2020

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Fluorinated compounds can exhibit interesting biological properties. The importance of these species has made that the chemistry of fluorine has experienced a great development. On this review, the recent advances on asymmetric fluorination reactions promoted by chiral hydrogen bonding-based organocatalysts are discussed. Hence, examples using phosphoric acid, carboxylic acid, (thio)urea and squaramide derivatives are illustrated. The growth of this field is amazing. We have only considered pivotal works in which direct fluorination takes place using a fluorinating agent, leaving aside the reactions where a fluorine atom is incorporated from the beginning as part of other reactants. Herein, the scarce existing examples on this field of research have been compiled.

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Enantioselective 5-exo-Fluorocyclization of Ene-Oximes

Cited by 26 publications

References 45 publications

Enantioselective halogenation via asymmetric phase‐transfer catalysis

Enantioselective halogenation via asymmetric phase‐transfer catalysis

Recent Developments in Enantioselective Organocatalytic Cascade Reactions for the Construction of Halogenated Ring Systems

Asymmetric Fluorination Reactions promoted by Chiral Hydrogen Bonding‐based Organocatalysts

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