Structure of nitrilimine: allenic or propargylic?

Wong, Ming Wah; Wentrup, Curt

doi:10.1021/ja00070a019

Cited by 38 publications

(25 citation statements)

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“…In the gas phase, 2Htautomers of 5-STs were 1.5-4 kcal mol -1 more thermodynamically stable than the 1H-forms. [115] The presence of an electron-withdrawing substituent at the 5position increases the polarity of the 2H-tautomer and also the relative proportion of the 2H-form in polar solvents. In media of high dielectric constant, 1H-tautomers are preferred due to their higher polarities.…”

Section: Alkylation Of 5-stsmentioning

confidence: 99%

Synthesis and Functionalization of 5‐Substituted Tetrazoles

2012

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Tetrazoles are synthetic heterocycles with numerous applications in organic chemistry, coordination chemistry, the photographic industry, explosives, and, in particular, medicinal chemistry. In organic chemistry, 5‐substituted tetrazoles are used as advantageous intermediates in the synthesis of other heterocycles and as activators in oligonucleotide synthesis. In drug design, 5‐monosubstituted tetrazoles are the most important tetrazole derivatives because they represent non‐classical bioisosteres of carboxylic acids, with similar acidities but higher lipophilicities and metabolic resistance. In this review we focus on the preparation and further functionalization of these heterocycles. Firstly, the role of 5‐substituted tetrazoles in medicinal chemistry is described, including examples of their effects on pharmacokinetics, pharmacodynamics, and metabolism of the associated drugs. Then, the main synthetic approaches to 5‐substituted tetrazoles – consisting of methods based on acidic media/proton catalysis, Lewis acids, and organometallic or organosilicon azides – are presented, from the early procedures to the most recent ones, with special attention paid to the reaction mechanisms. Functionalization of 5‐substituted tetrazoles is a challenging task because it usually leads to the formation of two isomers, 1,5‐ and 2,5‐disubstituted tetrazoles, in various ratios. In this overview, reactions with high or unusual regioselectivities are described, with comments on the possible mechanisms. Microwave‐assisted approaches to the synthesis and functionalization of 5‐substituted tetrazoles are also included.

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Section: Alkylation Of 5-stsmentioning

confidence: 99%

Synthesis and Functionalization of 5‐Substituted Tetrazoles

2012

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“…and 'all' mean CCSD(T) calculations correlating only valence and all electrons, respectively a Dihedral angles b Ref. [42] c Ref. [11] d Ref.…”

Section: Computational Detailsmentioning

confidence: 99%

“…These can be considered as conservative estimates, which also account for the approximations made and for neglecting higher-order correlation effects. From Tables 1, 2, 3, 4 and 5, it is evident that all isomers considered have been previously studied at different levels of theory [11,[41][42][43][44][45][46][47][48], but we report the first systematic investigation of their molecular structure. As in most cases the method and/or the basis set used are inferior to ours, a detailed comparison of these results to ours is not too meaningful.…”

Section: Molecular Structurementioning

confidence: 99%

A theoretical study on CH2N2 isomers: structure and energetics

Puzzarini

Gambi

2012

Theor Chem Acc

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Five CH2N2 isomers, namely cyanamide, carbodiimide, diazomethane, isocyanamide and nitrilimine, have been investigated at a high level of accuracy. The singles and doubles coupled-cluster method including a perturbational correction for connected triple excitations, CCSD(T), in conjunction with correlation-consistent basis sets ranging in size from triple to quintuple zeta have been employed. Extrapolation to the complete basis set limit has been used with treatments of core-valence correlation effects in order to accurately predict structures, relative energies as well as N-H and C-H bond dissociation energies. The latter required to also investigate the HNNC radical with the same methodology used for CH2N2 isomers, while HCNN and HNCN data are available in the literature by the same authors (Puzzarini and Gambi in J Chem Phys 122:064316, 2005). For all the species studied, harmonic vibrational frequencies have also been evaluated at the CCSD(T) level in order to obtain zero-point corrections to total energies

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“…[1,2,[13][14][15] Concerning nitrile imines, it is known that they exist as a single minimum on the potential energy surface, [16] which is best described by different resonance structures with different weights (Scheme 1). [19] Alternatively, a com- [ tally observed ν as (CNN) absorption at 1998 cm -1 and a carbenic resonance structure contribution of around 20 %, predicted by natural resonance theory calculations, demonstrate that the protoproduced C-amino nitrile imine has significant carbenic character. [17,18] Nevertheless, the structural nature of nitrile imines has been a subject of continuing debate, and it is not yet completely understood.…”

Section: Introductionmentioning

confidence: 99%

The Quest for Carbenic Nitrile Imines: Experimental and Computational Characterization of C‐Amino Nitrile Imine

et al. 2015

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C‐Amino nitrile imine has been generated as primary photoproduct (λ = 220 nm) of 5‐amino‐2H‐tetrazole isolated in an argon matrix at 15 K. Subsequent photochemical experiments (λ = 330 nm) demonstrated that C‐amino nitrile imine isomerizes to the corresponding three‐membered‐ring 1H‐diazirine and decomposes to methylenimine. The experimentally observed νas(CNN) absorption at 1998 cm–1 and a carbenic resonance structure contribution of around 20 %, predicted by natural resonance theory calculations, demonstrate that the protoproduced C‐amino nitrile imine has significant carbenic character. These results pave the way to the discovery of carbenic nitrile imines.

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Structure of nitrilimine: allenic or propargylic?

Cited by 38 publications

References 0 publications

Synthesis and Functionalization of 5‐Substituted Tetrazoles

Synthesis and Functionalization of 5‐Substituted Tetrazoles

A theoretical study on CH2N2 isomers: structure and energetics

The Quest for Carbenic Nitrile Imines: Experimental and Computational Characterization of C‐Amino Nitrile Imine

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