Kinetic and Mechanistic Studies of the Deuterium Exchange in Classical Keto−Enol Tautomeric Equilibrium Reactions

Nichols, M. A.; Waner, Mark J.

doi:10.1021/ed100292r

Cited by 30 publications

(36 citation statements)

References 6 publications

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“…When 3a was treated with D 2 O under the same conditions, deuteration was only detected at the α-positions of the carbonyl group (3a''). These results indicate that keto-enol tautomerism 47 promoted the deuteration at the α-positions of the carbonyl group, and this is consistent with the results of deuterated aldehydes 6r-6t (Fig. 2c).…”

Section: Resultssupporting

confidence: 89%

“…However, aliphatic aldehydes were less effective in the H/D exchange process, and only low deuterium incorporations in the aldehyde C-H bond (6r-6t) were achieved. This may be due to the keto-enol tautomerization of aliphatic aldehydes in the presence of excess D 2 O, 47 which was suggested by the deuteration of the α-positions of the formal groups. The successful H/D exchange also con rmed the formation of acyl radicals under light-promoted conditions.…”

Section: Resultsmentioning

confidence: 99%

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Bromine as a Visible-Light-Mediated Polarity-Reversal Catalyst for the Functionalization of Aldehydes

Wang

Liu

Huang

et al. 2020

Preprint

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Polarity-reversal catalysts enable otherwise sluggish or completely ineffective reactions which are characterized by unfavorable polar effects between radicals and substrates. We herein disclose for the first time that when irradiated by visible light, bromine can behave as a polarity-reversal catalyst. Hydroacylation of vinyl arenes, a three-component cascade transformation and deuteration of aldehydes were each achieved in a metal-free manner without initiators by using N-bromosuccinimide as the precatalyst. Light is essential to generate and maintain the active bromine radical during the reaction process. Another key to success is that HBr can behave as an effective hydrogen-donor to turn over the catalytic cycles.

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Section: Resultssupporting

confidence: 89%

Section: Resultsmentioning

confidence: 99%

Bromine as a Visible-Light-Mediated Polarity-Reversal Catalyst for the Functionalization of Aldehydes

Wang

Liu

Huang

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…Although no additional direct structural information could be obtained from NMR, the lower-than-expected integration of C8 methylene (CH 2 ) in the 1 H spectrum was suggestive of a β-dicarbonyl group. Methylene protons in this group exchange with the solvent through a ketoenol tautomerization mechanism resulting in lower integration (20). In addition, MS/MS analysis suggested the presence of a very labile carboxylic acid group and an acetyl group; malonyl groups are known to degrade easily to acetyl groups by loss of a carboxylic acid, thus corroborating the MS/MS data.…”

Section: Resultssupporting

confidence: 59%

Discovery of a novel amino acid racemase through exploration of natural variation in Arabidopsis thaliana

Strauch

Svedin

Dilkes

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Plants produce diverse low-molecular-weight compounds via specialized metabolism. Discovery of the pathways underlying production of these metabolites is an important challenge for harnessing the huge chemical diversity and catalytic potential in the plant kingdom for human uses, but this effort is often encumbered by the necessity to initially identify compounds of interest or purify a catalyst involved in their synthesis. As an alternative approach, we have performed untargeted metabolite profiling and genome-wide association analysis on 440 natural accessions of Arabidopsis thaliana. This approach allowed us to establish genetic linkages between metabolites and genes. Investigation of one of the metabolitegene associations led to the identification of N-malonyl-D-alloisoleucine, and the discovery of a novel amino acid racemase involved in its biosynthesis. This finding provides, to our knowledge, the first functional characterization of a eukaryotic member of a large and widely conserved phenazine biosynthesis protein PhzF-like protein family. Unlike most of known eukaryotic amino acid racemases, the newly discovered enzyme does not require pyridoxal 5′-phosphate for its activity. This study thus identifies a new D-amino acid racemase gene family and advances our knowledge of plant Damino acid metabolism that is currently largely unexplored. It also demonstrates that exploitation of natural metabolic variation by integrating metabolomics with genome-wide association is a powerful approach for functional genomics study of specialized metabolism.D-amino acid | racemase | genome-wide association | secondary metabolism | natural variation P lants have the ability to create over 200,000 small compounds known as secondary or specialized metabolites (1). These chemically diverse compounds help mediate plant adaptation to their environment and play important roles in plant defense mechanisms, pigmentation, and development. In addition, many of these metabolites are desirable to humans as medicinal and nutritional compounds. Therefore, furthering our understanding of plant specialized metabolism will have profound impacts on various applications from crop improvement to human health.To date, only a small fraction of the chemical and catalytic space in plant specialized metabolism has been explored. Even in the best-studied model plant Arabidopsis thaliana, there are still many uncharacterized metabolites, and the vast majority of genes encoding enzymes implied to be involved in specialized metabolism do not have known associations with any metabolites. Several studies of Arabidopsis natural accessions (individuals collected from wild populations) revealed considerable qualitative and quantitative variation in the accumulation of various compounds such as glucosinolates, terpenoids, and phenylpropanoids (2-4). This extensive metabolite variation can be attributed to genetic variation in genes encoding enzymes and regulatory factors of the pathways involved; quantitative trait locus (QTL) mapping has successfully uncove...

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“…Although the pK a difference between the two sites is only 1-2 units, this difference, when combined with the relative steric accessibility of the -protons, is usually enough to form selectively the kinetic enolate. The regioselectivity of this reaction is influenced by the reaction conditions [61,62]. Aprotic solvents such as tetrahydrofuran (THF) or diethyl ether favor the kinetic product (enolate) because the solvent carries no acidic hydrogen to favor the reverse reaction.…”

Section: Reversible Competitive First-order Reactionsmentioning

confidence: 99%

Practical Chemical Kinetics in Solution

Seoud

Baader

Bastos

2016

Encyclopedia of Physical Organic Chemistry, 5 Volume Set

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Kinetic and Mechanistic Studies of the Deuterium Exchange in Classical Keto−Enol Tautomeric Equilibrium Reactions

Cited by 30 publications

References 6 publications

Bromine as a Visible-Light-Mediated Polarity-Reversal Catalyst for the Functionalization of Aldehydes

Bromine as a Visible-Light-Mediated Polarity-Reversal Catalyst for the Functionalization of Aldehydes

Discovery of a novel amino acid racemase through exploration of natural variation in Arabidopsis thaliana

Practical Chemical Kinetics in Solution

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