2017
DOI: 10.1021/jacs.6b11851
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Catalytic Enantioselective [2,3]-Rearrangements of Allylic Ammonium Ylides: A Mechanistic and Computational Study

Abstract: A mechanistic study of the isothiourea-catalyzed enantioselective [2,3]-rearrangement of allylic ammonium ylides is described. Reaction kinetic analyses using 19F NMR and density functional theory computations have elucidated a reaction profile and allowed identification of the catalyst resting state and turnover-rate limiting step. A catalytically relevant catalyst–substrate adduct has been observed, and its constitution elucidated unambiguously by 13C and 15N isotopic labeling. Isotopic entrainment has shown… Show more

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Cited by 97 publications
(67 citation statements)
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“…Interception of a similar mechanistic pathway could be envisaged in the current study through base‐promoted elimination of pivalic acid from the in situ‐generated mixed anhydride 31 (Scheme , Path A ) . This mechanism would be of particular interest considering previous reports that suggest C(1)‐ammonium enolate catalysis most likely proceeds without the intermediacy of a ketene (see Scheme b) . However, based on the relative nucleophilicity of the pendant enamide, an ionic mechanism, either via ketene 32 (Scheme , Path B ), or through direct intramolecular addition of the enamide to the mixed anhydride (Scheme , Path C ), could also be considered.…”
Section: Resultsmentioning
confidence: 99%
“…Interception of a similar mechanistic pathway could be envisaged in the current study through base‐promoted elimination of pivalic acid from the in situ‐generated mixed anhydride 31 (Scheme , Path A ) . This mechanism would be of particular interest considering previous reports that suggest C(1)‐ammonium enolate catalysis most likely proceeds without the intermediacy of a ketene (see Scheme b) . However, based on the relative nucleophilicity of the pendant enamide, an ionic mechanism, either via ketene 32 (Scheme , Path B ), or through direct intramolecular addition of the enamide to the mixed anhydride (Scheme , Path C ), could also be considered.…”
Section: Resultsmentioning
confidence: 99%
“…Originating from anti‐bonding σ * orbitals, chalcogen bonds extend linearly from the covalent bonds (bond angle Φ 1 ~ 180°) and thus appear on the side of the chalcogen atom (bond angle Φ 2 ~ 70°, Figure ,a ) . They have been studied extensively in crystal engineering and for intramolecular conformational control in solution, including prominent use in medicinal chemistry and pioneering applications in covalent catalysis . The use of intermolecular chalcogen bonds in functional systems in solution is rare and recent, non‐covalent chalcogen‐bonding catalysis has been introduced only last year.…”
Section: Methodsmentioning
confidence: 99%
“…They have been studied extensively in crystal engineering and for intramolecular conformational control in solution, including prominent use in medicinal chemistry and pioneering applications in covalent catalysis . The use of intermolecular chalcogen bonds in functional systems in solution is rare and recent, non‐covalent chalcogen‐bonding catalysis has been introduced only last year. [ ][ ][ ] The key to success was the idea that the somewhat awkwardly ‘hidden’ position of the σ holes on the side of chalcogen‐bond donors turns into an advantage as soon as transition‐state recognition in the focal point of two adjacent donors is considered .…”
Section: Methodsmentioning
confidence: 99%
“…[14,15] This versatile platform proceeds via the union of C1-ammonium enolate nucleophiles [16,17] and p(allyl)Pd electrophiles, [18] and provides highly enantioenriched and functionalized a-branched esters that can be readily diversified without compromising optical purity. [14,15] This versatile platform proceeds via the union of C1-ammonium enolate nucleophiles [16,17] and p(allyl)Pd electrophiles, [18] and provides highly enantioenriched and functionalized a-branched esters that can be readily diversified without compromising optical purity.…”
Section: Reaction Designmentioning
confidence: 99%