Reported is the enantioselective synthesis of tetracyclic indolines using silver(I)/chiral phosphoric acid catalysis. A variety of alkyne‐tethered indoles are suitable for this process. Mechanistic ...studies suggest that the in situ generated silver(I) chiral phosphate activates both the alkyne and the indole nucleophile in the initial cyclization step through an intermolecular hydrogen bond and the phosphate anion promotes proton transfer. In addition, further modifications of the cyclization products enabled stereochemistry–function studies of a series of bioactive indolines.
Duality: Highly enantioselective synthesis of tetracyclic indolines was realized using cooperative silver(I)/chiral phosphoric acid catalysis. Mechanistic studies identified the dual role of the chiral phosphate. M.S.=molecular sieves.
DFT computations reveal different reaction mechanisms for the oxidative addition of C(sp
)-F and C(sp
)-F bonds to the Al(i) complexes: a concerted mechanism for C(sp
)-F and a stepwise mechanism for ...C(sp
)-F involving fluoride transfer and the formation and recombination of an ion pair.
We present a detailed DFT mechanistic study on the first Ni-catalyzed direct carbonyl-Heck coupling of aryl triflates and aldehydes to afford ketones. The precatalyst Ni(COD)
2
is activated with the ...phosphine (phos) ligand, followed by coordination of the substrate PhOTf, to form Ni(phos)(PhOTf) for intramolecular PhOTf to Ni(0) oxidative addition. The ensuing phenyl-Ni(
ii
) triflate complex substitutes benzaldehyde for triflate by an interchange mechanism, leaving the triflate anion in the second coordination sphere held by Coulomb attraction. The Ni(
ii
) complex cation undergoes benzaldehyde C&z.dbd;O insertion into the Ni-Ph bond, followed by β-hydride elimination, to produce Ni(
ii
)-bound benzophenone, which is released by interchange with triflate. The resulting neutral Ni(
ii
) hydride complex leads to regeneration of the active catalyst following base-mediated deprotonation/reduction. The benzaldehyde C&z.dbd;O insertion is the rate-determining step. The triflate anion, while remaining in the second sphere, engages in electrostatic interactions with the first sphere, thereby stabilizing the intermediate/transition state and enabling the desired reactivity. This is the first time that such second-sphere interaction and its impact on cross-coupling reactivity has been elucidated. The new insights gained from this study can help better understand and improve Heck-type reactions.
We present a detailed DFT mechanistic study on the first Ni-catalyzed direct carbonyl-Heck coupling of aryl triflates and aldehydes to afford ketones.
A novel complex comprising an ion pair of arginine–arginine carbamate is reported herein, which is isolated from an aqueous l-arginine solution after reacting with CO2. Its structure was ...unambiguously elucidated via single-crystal X-ray diffraction, and its phase purity was confirmed by powder X-ray diffraction (PXRD) analysis. Nuclear magnetic resonance (NMR) studies suggested that the arginine carbamate complex hydrolyzed in aqueous conditions with a rate directly proportional to its concentration. Furthermore, density functional theory (DFT) calculations revealed how the amino group acted as a nucleophile to attack CO2 to enable the ion-pair formation through a proton transfer between the arginine and arginine carbamate. The discovery of the arginine–CO2 adduct expands our understanding of CO2 fixation and can lead to the development of new methods of implementing l-arginine or other amino acids for CO2 capture technology.
DFT computations reveal different reaction mechanisms for the oxidative addition of C(sp
2
)-F and C(sp
3
)-F bonds to the Al(
i
) complexes: a concerted mechanism for C(sp
2
)-F and a stepwise ...mechanism for C(sp
3
)-F involving fluoride transfer and the formation and recombination of an ion pair.
DFT computations reveal different reaction mechanisms for the oxidative addition of C(sp
2
)-F and C(sp
3
)-F bonds to the Al(
i
) complexes: a concerted mechanism for C(sp
2
)-F and a stepwise mechanism for C(sp
3
)-F involving fluoride transfer and the formation and recombination of an ion pair.
Reported is the enantioselective synthesis of tetracyclic indolines using silver(I)/chiral phosphoric acid catalysis. A variety of alkyne‐tethered indoles are suitable for this process. Mechanistic ...studies suggest that the in situ generated silver(I) chiral phosphate activates both the alkyne and the indole nucleophile in the initial cyclization step through an intermolecular hydrogen bond and the phosphate anion promotes proton transfer. In addition, further modifications of the cyclization products enabled stereochemistry–function studies of a series of bioactive indolines.
Dual und kooperativ: Eine hoch enantioselektive Synthese tetracyclischer Indoline beruht auf kooperativer Katalyse mit Silber(I) und einem chiralen Phosphorsäurederivat. Mechanistische Untersuchungen offenbaren eine doppelte Rolle des chiralen Phosphats.
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