Electrochemical oxidation of 4-monoalkyl-substituted 1,4-dihydropyridines

Abstract

The electrochemical oxidation of 4-monoalkyl-substituted 1,4-dihydropyridines has been studied in an aprotic medium and in the presence of pyridine. In an aprotic medium the products of oxidation are both 4-alkyl-substituted and 4-unsubstituted pyridines or mixtures of them. On oxidation in acetonitrile of 4- 2,3, were obtained in addition to the oxidized forms. In the presence of base the products of preparative electrolysis of the studied compounds were 4-alkyl-substituted pyridines. The exception was the 4-i-Prsubstituted dihydropyridine which was dealkylated on oxidation even in the presence of base.Dihydropyridines are one of the most investigated classes of organic compounds. The synthesis and reactions of 1,4-dihydropyridines have been examined in detail in reviews [1][2][3][4]. Many compounds of this series possess pharmacological activity. A series of pharmaceuticals [5] has been developed based mainly on 4-arylsubstituted 1,4-dihydropyridines. Antioxidant properties have also been confirmed for the heterocycle itself in reactions with various radicals [6,7]. On the other hand study of the redox reaction of the dihydropyridine ring is also important for the reason that its oxidation is the main metabolism of dihydropyridines.The attention of electrochemists is mainly attracted [8][9][10][11][12][13] by the oxidation of 4-methyl-, 4-aryl-1,4-dihydropyridines or those unsubstituted in position 4. In all the mentioned cases proton is split off from the position 4 of the ring on oxidation. N Me H Me R H COOMe MeOOC 1-5 1 R = Me, 2 R = Et, 3 R = n-Pr, 4 R = i-Pr, 5 R = i-Bu

Evaluation of Physicochemical Properties of Amphiphilic 1,4-Dihydropyridines and Preparation of Magnetoliposomes

“…These data were also in agreement with our previous results, where the electrochemical oxidation potential of a similar cationic 1,4-DHP was determined as 1.7 V, and the electrochemical oxidation of this compound was characterized as a two-electron process [50], whereas the parent compounds-1,4-DHP derivatives without cationic moieties demonstrated lower electrooxidation potentials. Thus, 4-phenyl substituted Hantzsch 1,4-dihydropyridine had a potential of 1.08 V [51], and other different 4-aryl substituted 1,4-DHPs had potentials around 1.1 V [52], but 4-monoalkyl substituted 1,4-DHPs had oxidation potentials of 1.01-1.03 V, respectively [53].…”

Visible-Light-Induced Alkoxyl Radicals Enable α-C(sp3)-H Bond Allylation

“…From computational studies, the N-alkoxylphthalimide 1 first undergoes single electron reduction to generate the radical anion CP1 . After protonation by the Hantzsch ester radical cation, the alkyl radical intermediate CP2 was formed with 5.8 kcal/mol endothermically (black line) (Azizi et al., 2015, McSkimming and Colbran, 2013, Zheng and You, 2012, Turovska et al., 2008, Zhu et al., 1999). The N-O bond was then homolytically cleaved to form the alkoxyl radical CP3 via the transition state TS1 with an activation energy of 18.8 kcal/mol.…”

Pleiotropic Properties of Amphiphilic Dihydropyridines, Dihydropyridones, and Aminovinylcarbonyl Compounds

“…It should be noted that the parent compounds—1,4-DHP derivatives without cationic moieties—demonstrated lower electrooxidation potentials. Thus, 4-phenyl-substituted Hantzsch 1,4-dihydropyridine has a 1.08 V potential on a glassy carbon electrode [ 50 ] and the other 4-aryl-substituted 1,4-DHPs have 1.11 V potentials [ 51 ], but 4-monoalkyl-substituted 1,4-dihydropyridines at the same conditions have 1.01–1.03 V oxidation potentials [ 47 ].…”