Tautomerism: Introduction, History, and Recent Developments in Experimental and Theoretical Methods

Taylor, Peter J.; Zwan, Gert van der; Antonov, Liudmil

doi:10.1002/9783527658824.ch1

Cited by 40 publications

(59 citation statements)

References 92 publications

(97 reference statements)

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“…Tautomerization has been studied by using UV-vis spectroscopy, NMR, X-ray diffraction, and theoretical calculations [68]. Two types of tautomerization are common in chemistry; transformation between amino and imino tautomers, and between enol and keto tautomers.…”

Section: Intramolecular H-atom Transfer Reactionsmentioning

confidence: 99%

Direct observation and control of hydrogen-bond dynamics using low-temperature scanning tunneling microscopy

Kumagai

2015

Progress in Surface Science

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Section: Intramolecular H-atom Transfer Reactionsmentioning

confidence: 99%

Direct observation and control of hydrogen-bond dynamics using low-temperature scanning tunneling microscopy

Kumagai

2015

Progress in Surface Science

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“…Regarding the structural aspect, tautomerism is divided into four main types: annular tautomerism, side-chain tautomerism, ring-chain tautomerism and valence tautomerism. In the first type, as the name suggests, the alterations occur within the ring system, between annular carbon and heteroatoms such as nitrogen and oxygen; in the second type, the side-chain elements participate in the interconversion involving the ring; the other two types are characterized by transformations leading to bond formation or rupture-while in ring-chain tautomerism, the migration of the species on the side chain results in ring closure, the valence tautomerism is not a result of migrations of any group or element but rather a rupture or formation of bonds carried by an energetic stimulus [47][48][49][50]. Regarding the type of element involved in the interconversion, tautomerism can be subdivided into prototropy, when the exchange is characterized by the displacement of a proton between two positions suffering alteration, elementotropy, when a heavier element participates in the transformation, frequently a metal atom (metallotropy), and aniontropy and cationtropy, where the two isomers differ only on the position of an anion or cation, respectively [42,49,51,52].…”

Section: Tautomerism In Pyrazolesmentioning

confidence: 99%

Revisiting the Structure and Chemistry of 3(5)-Substituted Pyrazoles

2019

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Pyrazoles are known as versatile scaffolds in organic synthesis and medicinal chemistry, often used as starting materials for the preparation of more complex heterocyclic systems with relevance in the pharmaceutical field. Pyrazoles are also interesting compounds from a structural viewpoint, mainly because they exhibit tautomerism. This phenomenon may influence their reactivity, with possible impact on the synthetic strategies where pyrazoles take part, as well as on the biological activities of targets bearing a pyrazole moiety, since a change in structure translates into changes in properties. Investigations of the structure of pyrazoles that unravel the tautomeric and conformational preferences are therefore of upmost relevance. 3(5)-Aminopyrazoles are largely explored as precursors in the synthesis of condensed heterocyclic systems, namely pyrazolo[1,5-a]pyrimidines. However, the information available in the literature concerning the structure and chemistry of 3(5)-aminopyrazoles is scarce and disperse. We provide a revision of data on the present subject, based on investigations using theoretical and experimental methods, together with the applications of the compounds in synthesis. It is expected that the combined information will contribute to a deeper understanding of structure/reactivity relationships in this class of heterocycles, with a positive impact in the design of synthetic methods, where they take part.

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“…T he analysis of tautomers-isomeric species that differ only in the positioning of a labile proton [1] -has challenged mass spectrometry (MS) for many decades [2,3]. In rare cases, orthogonal separation of tautomers prior to MS analysis could be afforded by gas chromatography [4], but the vast majority of cases involve MS analysis of convolved mixtures of tautomers.…”

Section: Introductionmentioning

confidence: 99%

Studying Gas-Phase Interconversion of Tautomers Using Differential Mobility Spectrometry

Campbell

Yang

Melo

et al. 2016

J. Am. Soc. Mass Spectrom.

123

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Abstract. In this study, we report on the use of differential mobility spectrometry (DMS) as a tool for studying tautomeric species, allowing a more in-depth interrogation of these elusive isomers using ion/molecule reactions and tandem mass spectrometry. As an example, we revisit a case study in which gas-phase hydrogendeuterium exchange (HDX)-a probe of ion structure in mass spectrometry-actually altered analyte ion structure by tautomerization. For the N-and O-protonated tautomers of 4-aminobenzoic acid, when separated using DMS and subjected to subsequent HDX with trace levels of D 2 O, the anticipated difference between the exchange rates of the two tautomers is observed. However, when using higher levels of D 2 O or a more basic reagent, equivalent and almost complete exchange of all labile protons is observed. This second observation is a result of the interconversion of the N-protonated tautomer to the Oprotonated form during HDX. We can monitor this transformation experimentally, with support from detailed molecular dynamics and electronic structure calculations. In fact, calculations suggest the onset of bulk solution phase properties for 4-aminobenzoic acid upon solvation with eight CH 3 OH molecules. These findings also underscore the need for choosing HDX reagents and conditions judiciously when separating interconvertible isomers using DMS.

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Tautomerism: Introduction, History, and Recent Developments in Experimental and Theoretical Methods

Cited by 40 publications

References 92 publications

Direct observation and control of hydrogen-bond dynamics using low-temperature scanning tunneling microscopy

Direct observation and control of hydrogen-bond dynamics using low-temperature scanning tunneling microscopy

Revisiting the Structure and Chemistry of 3(5)-Substituted Pyrazoles

Studying Gas-Phase Interconversion of Tautomers Using Differential Mobility Spectrometry

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