Recent Developments in the Nitroxide‐Catalyzed Oxidation of Amines: Preparation of Imines and Nitriles

Bartelson, Ashley L.; Lambert, Kyle M.; Bobbitt, James M.; Bailey, William F.

doi:10.1002/cctc.201600858

Cited by 30 publications

(18 citation statements)

References 68 publications

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“…2,2,6,6-tetramethylpiperidine N-oxyl is widely known as an oxidation catalyst for alcohols, but it can also electrochemically oxidize amines [35]. However, the reaction is limited to organic solvents and basic aqueous solutions.…”

Section: Resultsmentioning

confidence: 99%

“…The nitroxyl radical moiety was oxidized at the electrode surface to an oxoammonium ion, which is the active form. The oxoammonium ion reportedly binds to a primary amine in aqueous solution resulting in the disappearance of catalytic activity [38][39][40] (Note: TEMPO oxidizes primary amines in acetonitrile [35]). Likewise, the oxoammonium ion of NNO bonds with ethylamine in aqueous solution causing the catalytic activity to disappear ( Figure 4).…”

Section: Resultsmentioning

confidence: 99%

“…Even upon addition of each amine, this anodic peak did not increase in response current (ΔIp) compared with that without amine. Although TEMPO has sufficient oxidation catalytic ability in organic solvents [35], it could not oxidize amines under physiological conditions and was difficult to use for electrochemical analysis under these conditions. Nortropine N-oxyl can be an electroanalysis probe for chemical compounds having secondary or tertiary amines or isopropylamine structures under physiological conditions.…”

Section: Resultsmentioning

confidence: 99%

“…Superiority of NNO was demonstrated from this report [27]. In contrast, TEMPO has catalytic oxidation ability toward amines as well as alcohols [35][36][37]. Therefore, the present study examined the electrolytic oxidation effect of NNO on amines under physiological conditions and compared the results with those obtained with TEMPO.…”

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Electrochemical Oxidation of Amines Using a Nitroxyl Radical Catalyst and the Electroanalysis of Lidocaine

et al. 2018

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The nitroxyl radical of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) can electro-oxidize not only alcohols but also amines. However, TEMPO has low activity in a neutral aqueous solution due to the large steric hindrance around the nitroxyl radical, which is the active site. Therefore, nortropine N-oxyl (NNO) was synthesized to improve the catalytic ability of TEMPO and to investigate the electrolytic oxidation effect on amines from anodic current changes. Ethylamine, diethylamine, triethylamine, tetraethylamine, isopropylamine, and tert-butylamine were investigated. The results indicated that TEMPO produced no response current for any of the amines under physiological conditions; however, NNO did function as an electrolytic oxidation catalyst for diethylamine, triethylamine, and isopropylamine. The anodic current depended on amine concentration, which suggests that NNO can be used as an electrochemical sensor for amine compounds. In addition, electrochemical detection of lidocaine, a local anesthetic containing a tertiary amine structure, was demonstrated using NNO with a calibration curve of 0.1-10 mM.around the nitroxyl radical active site, and an adequate response current could not be obtained under physiological conditions. Iwabuchi and colleagues [22] reported that 2-azaadamantane N-oxyl (AZADO), which lacks steric hindrance around the active site, exhibited greater activity than TEMPO in organic synthesis reactions. Less-hindered nitroxyl radicals with various steric environments have been synthesized, and those with less bulky functionality exhibited greater activity [23][24][25][26]. Therefore, nortropine N-oxyl (NNO), which was modeled on AZADO, was synthesized in one step as a novel nitroxyl radical compound [27]. The NNO was capable of electrolytic oxidation of alcohols in neutral aqueous solutions. The NNO could be used in place of enzymes, allowing non-enzymatic analysis of glucose under physiological conditions [27]. Phenylboronic acid derivatives have been investigated as glucose sensors [28][29][30]. Phenylboronic acid (PBA) spontaneously binds with a moiety containing a diol [31]. The structural and electrical changes in PBA derivative probes when PBA bonds with the diol moiety can be used for glucose detection [32][33][34]. However, these probes had low specificity for glucose and did not respond under physiological conditions. Superiority of NNO was demonstrated from this report [27]. In contrast, TEMPO has catalytic oxidation ability toward amines as well as alcohols [35][36][37]. Therefore, the present study examined the electrolytic oxidation effect of NNO on amines under physiological conditions and compared the results with those obtained with TEMPO. The results demonstrated that NNO was a good electrochemical analysis probe for secondary and tertiary amines and for isopropylamine under physiological conditions (Figure 1). The oxoammonium ion, which is the active species, reacts with the amine to form hydroxylamine. The catalyst regenerates by reoxidation of hydroxylamine. Furthermore, ele...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 80%

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Electrochemical Oxidation of Amines Using a Nitroxyl Radical Catalyst and the Electroanalysis of Lidocaine

et al. 2018

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“…21 Stable nitroxyl radical TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) plays a salient role as catalyst in metal-, organo-or biocatalysed oxidation processes and signicant progress in terms of catalytic efficiency and substrate applicability has been achieved, 22 including oxidation of amines. 23 Concerning the bio-oxidation of amines, Contente et al reported an application of a ow-based biocatalysis in the oxidation of amines to aldehydes by an immobilized transaminase with sodium pyruvate as co-oxidant, 24 and Zheng et al reported the a-oxydation of cyclic amines to amides by whole-cell biotransformation. 25 Using metal-free oxidants, Gaspa et al reported a mild and solvent-free oxidation of primary amines to aldehydes, ketones, and nitriles by N-chlorosuccinimide under ballmilling conditions.…”

Section: Introductionmentioning

confidence: 99%