Silver‐Catalyzed Allenylation and Enantioselective Propargylation Reactions of Ketones

Kohn, Benjamin; Ichiishi, Naoko; Jarvo, Elizabeth R.

doi:10.1002/ange.201206971

Cited by 9 publications

(2 citation statements)

References 54 publications

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“…Inspired by the Feng and Lohs elegant work on the racemic synthesis of non-symmetric a,a-disubstituted trifluoroethane derivatives, [7b] we became interested in whether chiral ligands could be applied to the palladium-catalyzed asymmetric fluoroarylation of gem-difluoroalkenes with aryl halides. However, this hypothesis faced considerable challenges (Scheme 1 d): 1) catalytic amount of chiral ligand versus an excess amount of AgF will make the intermediate I may have no chiral ligand; 2) AgF competitive binding with palladium to chiral ligand, [16] it may weaken or even completely eliminate the enantioselectivity of this reaction; 3) according to Hus findings, [5] intermediate I can generate trifluorobenzyl radical, which will lead to the racemization of intermediate I; 4) referring to the work of Tredwell [13c] and Jarvo, [17] the intermediate II may also undergo racemization for the same reason; 5) how to avoid hydrofluorination [18] of intermediate I rather than the transmetalation; 6) how to avoid b-H elimination of intermediate II when the R is alkyl group.…”

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Design and Synthesis of TY‐Phos and Application in Palladium‐Catalyzed Enantioselective Fluoroarylation ofgem‐Difluoroalkenes

Lin

Pan

et al. 2020

Angew Chem Int Ed

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The first example of highly enantioselective fluoroarylation of gem-difluoroalkenes with aryl halides is presented by using a new chiral sulfinamide phosphine (Sadphos) type ligand TY-Phos. N-Me-TY-Phos can be easily synthesized on a gram scale from readily available starting materials in three steps. Salient features of this work including readily available starting materials, good yields, high enantioselectivities as well as broad substrate scope make this approach very practical and attractive. Notably, the asymmetric synthesis of an analogue of a biologically active molecule is also reported. The gem-difluoroalkenes are increasingly being exploited as versatile fluorinated building blocks in organofluorine synthesis [1] via mono-defluorinative [2] or fluorine retentive [3] functionalization reactions. Over the past decade, by taking advantage of easily available gem-difluoroalkenes as reliable trifluoromethyl (CF 3) precursors, many chemists reported a conceptually novel protocol for the expedient synthesis of CF 3-containing molecules through an additional fluorine source via a radical pathway or an anion/ cation mechanism (Scheme 1),which are supplement to the typical trifluoromethylation reaction. [4] In 2014, Hu and co-workers demonstrated the formation of a-trifluoromethylated benzylsilver species from the reaction of gem-difluoroalkene with AgF for the first time, and which undergoes rapid C-Ag I bond homolysis in situ to afforded the a-CF 3 benzyl radical. [5] Recently, Feng et al. [6] reported a photoredox-coupled Fnucleophilic addition induced allylic alkylation of gemdifluoroalkenes via the a-CF 3 benzyl radical intermediate (Scheme 1 a). In contrast, the Feng and Loh group [7] and Malcolmson et al. [8] realized palladium-catalyzed fluorinative allylation and arylation of gem-difluoroalkenes via a-CF 3 carbanion intermediate, and the first attempt to palladiumcatalyzed asymmetric fluoroallylation of gem-difluoroalkenes Scheme 1. Trifluoromethylation of gem-difluoroalkenes.

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confidence: 99%

Design and Synthesis of TY‐Phos and Application in Palladium‐Catalyzed Enantioselective Fluoroarylation ofgem‐Difluoroalkenes

Lin

Pan

et al. 2020

Angew Chem Int Ed

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“…Compared with other types of ketones, the catalytic enantioselective propargylation of diaryl ketones was much more difficult due to the smaller size difference between the two aryl groups. Jarvo and co‐workers made a breakthrough on this challenge reaction . They recently discovered that a variety of diaryl‐substituted homopropargyl tertiary alcohols 55 could be formed with up to 95% yield and 97% ee value when 5 mol% of AgF, 5 mol% of ( R , R )‐Walphos 54 and 30 mol% of t‐ BuONa were applied (Scheme ).…”

Section: Catalytic Asymmetric Nucleophilic Addition Of Organometallicmentioning

confidence: 99%

Recent Advances in Catalytic Asymmetric Synthesis of Tertiary Alcohols via Nucleophilic Addition to Ketones

2018

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Chiral tertiary alcohols are an important class of organic compounds which have found wide applications in both academia and industry. Therefore, various synthetic strategies towards these compounds have already been developed. Among them, the catalytic asymmetric addition of carbon nucleophiles to ketones is the most desirable route owing to its straightforwardness as well as its economic, efficient and versatile advantages. This review summarizes and discusses the recent achievements in this field classified according to the reaction types. Special attention is paid to the mechanisms, advantages and limitations of each reaction. In addition, the applications of these catalytic processes in the synthesis of related natural products, pharmaceuticals or their analogues are briefly discussed as well.

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Silver‐Catalyzed Transformation of Propargylic Amine N‐Oxides to Enones and Acyloxy Ketones via Isoxazolinium Intermediates

Cui¹,

Kung²,

Ko³

et al. 2014

Adv Synth Catal

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A novel silver-catalyzed transformation of propargylic amine N-oxides with switchable product profiles has been developed. A diversity of enones with excellent E/Z ratios (up to > 20:1) were obtained when the reactions were conducted in aprotic solvents. In contrast, 3-chlorobenzoxymethyl ketones and a-(3-chloro)-benzoxy enones were obtained by using protic solvents. Mechanistic studies suggested that in situ generated isoxazolinium ions are the key intermediates involved in these novel silver-catalyzed reaction pathways. Applications on the chemoselective modification of cysteine-containing peptides in aqueous medium have also been achieved. COMMUNICATIONS Jian-Fang Cui et al. Scheme 2. A proposed reaction mechanism.

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Silver‐Catalyzed Allenylation and Enantioselective Propargylation Reactions of Ketones

Cited by 9 publications

References 54 publications

Design and Synthesis of TY‐Phos and Application in Palladium‐Catalyzed Enantioselective Fluoroarylation ofgem‐Difluoroalkenes

Design and Synthesis of TY‐Phos and Application in Palladium‐Catalyzed Enantioselective Fluoroarylation ofgem‐Difluoroalkenes

Recent Advances in Catalytic Asymmetric Synthesis of Tertiary Alcohols via Nucleophilic Addition to Ketones

Silver‐Catalyzed Transformation of Propargylic Amine N‐Oxides to Enones and Acyloxy Ketones via Isoxazolinium Intermediates

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