- Rate of formation of N-(hydroxymethyl)benzamide derivatives in water as a function of pH and their equilibrium constants
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The third-order rate constants for the pH-dependent formation of the carbinolamides generated from the reaction of formaldehyde and benzamide, 4-chloro, 4-nitro, 4-methyl and 4-methoxybenzamide, are reported. The acid-catalyzed reaction was found to occur via rate-limiting proton transfer, whereas the hydroxide-dependent reaction occurred via a specific-base process. Coupling the rate constants for carbinolamide formation reported herein with the previously established rates for carbinolamide breakdown yielded equilibrium constants for the carbinolamides studied in water.
- Ankem, Ramana V.,Murphy, John L.,Nagorski, Richard W.
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- Application of chiral triazole-substituted iodoarenes in the enantioselective construction of spirooxazolines
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A catalytic highly enantioselective synthesis of spirooxazolines is presented. Starting from readily available 2-naphthol-substituted benzamides and using catalytic amounts of a chiral triazole-substituted iodoarene catalyst, a variety of spirooxazolines
- Abazid, Ayham H.,Nachtsheim, Boris J.
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supporting information
p. 8822 - 8825
(2021/09/07)
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- A convenient and clean synthesis of methylenebisamides and carbinolamides over zeolites in aqueous media
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A simple, efficient and environmentally benign protocol for the synthesis of methylenebisamides and carbinolamides in high yields from aromatic amides and formaldehyde in the presence of heterogeneous catalysts (Hβ and NaY zeolites) using water as a solvent is demonstrated. Moreover, the catalyst is recyclable and can be reused without significant loss in its catalytic activity.
- Mameda, Naresh,Marri, Mahender Reddy,Peraka, Swamy,Macharla, Arun Kumar,Kodumuri, Srujana,Chevella, Durgaiah,Naresh, Gutta,Nama, Narender
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- Rapid amidic hydrolysis: a competitive reaction pathway under basic conditions for N-(hydroxymethyl)benzamide derivatives bearing electron-donating groups
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Studies of N-(hydroxymethyl)benzamide derivatives have concluded that the hydroxide-dependent reaction occurs via a specific-base catalyzed deprotonation of the hydroxyl group followed by rate-determining loss of the benzamidate and generation of the aldehyde. The 3-methyl, 4-methyl, and 4-methoxy-N-(hydroxymethyl)benzamide reaction mechanism deviates at higher [HO-] with amidic hydrolysis becoming competitive and having reaction half-lives of ~17 s, in 1 M KOH, I = 1.0 M (KCl), 25 °C. An intramolecular general-base catalyzed mechanism has been suggested for the amidic hydrolysis reaction.
- Murphy, John L.,Tenn III, William J.,Labuda, Joseph J.,Nagorski, Richard W.
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supporting information; experimental part
p. 7358 - 7361
(2010/03/03)
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- Acyloxymethyl as a Drug Protecting Group. Kinetics and Mechanism of the Hydrolysis of N-Acyloxymethylbenzamides
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Acyloxymethyl derivatives of secondary and tertiary amides undergo hydrolysis via acid-catalysed, base-catalysed and pH-independent processes.The pH-independent pathway involves rate-limiting iminium ion formation and is characterised by the following: a Hammett ρ value for the substituent in the benzamide moiety of ca. -1.2 for both types of substrate; the absence of general-base or nucleophilic catalysis; a common benzoate ion effect; a solvent deuterium isotope effect, kobsH2O/kobsD2O, of ca. 1.6; Σ(excit.) values of -4 and -12 J k-1 mol-1 for secondary and tertiary substrates respectively; and higher reactivity of the tertiary amides over their secondary counterparts.The acid-catalysed process involves protonation of the substrate followed by iminium ion formation, and is characterised by the following: a Hammett ρ value of ca. -1.5 for the substitutent effect of the benzamide moiety; a solvent deuterium isotope effect of ca. 0.4; a monotonic rise in the pseudo-first-order rate constant kobs with increasing ; ΔS(excit.) values > 0 J K-1 mol-1; higher reactivity of the tertiary substrates over their secondary counterparts; and a value of 0.85 for the Bronsted coefficient, βlg, for the carboxylate nucleofuge.The base-catalysed hydrolysis of tertiary substrates involves normal ester hydrolysis via acyl-oxygen bond cleavage, and is characterised by a Hammett ρ value of +0.38, a solvent deuterium isotope effect, kOH-/kOD-, of 0.85, and a ΔS(excit.) balue of -96 J K-1 mol-1.The corressponding base-catalysed process for the secondary substrates involves imine formation via an E2 elimination reaction.The secondary acyloxymethylamides are some 7 * 104 times more reactive than their tertiary counterparts in the base-catalysed region.Hammett ρ values of +1.1 and +0.6 are obtained for the substituents in the base-catalysed region.Hammett ρ values of +1.1 and +0.6 are obtained for the substituents in the ester and amide moieties, respectively.Buffer catalysis is observed, and the value of ca. 0.5 for the Bronsted β coefficient identifies the amide proton as approximately 50percent transferred to the buffer species in the transition state.Heats of formation, ΔHf, calculated using the AM1 SCF MO package reveal that iminium ion formation is thermodynamically equi-energetic for cyclic and acyclic systems.Iminium ion formation from tertiary substrates is favoured by ca. 25 kJ mol-1 over the corresponding secondary analogues.
- Iley, Jim,Moreira, Rui,Rosa, Eduarda
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p. 563 - 570
(2007/10/02)
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