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Kinetic and mechanistic investigation on the oxidation of Hantzsch 1,4-dihydropyridines with the tropylium cation: a model for NADH oxidation

✍ Scribed by Bingjun Zhao; Xiaoqing Zhu; Yun Lu; Chi-Zhong Xia; Jin-Pei Cheng

Publisher
Elsevier Science
Year
2000
Tongue
French
Weight
98 KB
Volume
41
Category
Article
ISSN
0040-4039

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✦ Synopsis

The reaction kinetics of the reactions of Hantzsch esters (HEH) and Hantzsch 4-aryl-1,4-dihydropyridines (4aryl-HEH) with the tropylium cation as a formal hydride acceptor were investigated. The observed kinetic isotope effect (KIE, k H /k D ), using HEH and 4,4-d 2 -HEH as substrates, was 4.16, suggesting that the C-H bond cleavage was involved in the rate-limiting step. Correlation analysis on the reactions of para-substituted Hantzsch 4-aryl-1,4-dihydropyridines generated a linear Hammett plot (r=0.9946), with ρ equal to -1.16, which is also consistent with the one-step hydride removal (from 4-C) mechanism. Comparisons of the kinetics and of the reaction thermodynamics between the reactions of HEH and 4-phenyl-HEH both disfavor the one-electron-transfer-initiated multistep mechanism.

πŸ“œ SIMILAR VOLUMES

Studies on novel and chiral 1,4-dihydrop
Studies on novel and chiral 1,4-dihydropyridines. IV. Mechanistic aspects of the asymmetric reduction with chiral NADH model compounds, (SS)-3-(p-tolylsulfinyl)-1,4-dihydropyridines
✍ Satoshi Obika; Toshihiko Nishiyama; Satoshi Tatematsu; Kazuyuki Miyashita; Takes πŸ“‚ Article πŸ“… 1997 πŸ› Elsevier Science 🌐 French βš– 537 KB

In the reduction of ketones with NADH mimics, (Ss)-l-substituled 3-(p-tolylsulfinyl)-1,4-dihydropyridines 1, the stereospecific transfer of one of the C-4 hydrogens, which is syn to the S-O bond, was experimentally revealed to be involved by employing the 2-methyl derivative 2 and the 4-deuterated d