Tautomeric Equilibria in Solutions of 2-Phenacylbenzimidazoles

IF 1.1 4区化学 Q3 CHEMISTRY, MULTIDISCIPLINARY

Heteroatom Chemistry Pub Date : 2019-02-03 DOI:10.1155/2019/4364207

Agnieszka Skotnicka, Przemysław Czeleń, R. Gawinecki

引用次数: 3

Abstract

Detailed NMR spectral analysis of DMSO-d6 solutions of the series of substituted 2-phenacylbenzimidazoles (ketimine form, K) reveals two from three tautomeric forms. Integrals of the 1H NMR signals are used in establishing the molar ratio of tautomers. The experimental analyses are supported by quantum-chemical calculations, which satisfactorily reproduced the experimental trends. Although the reported semiempirical quantum-chemical calculations show that enaminone E, i.e., 2-(1,3-dihydro-2H-benzo[d]imidazol-2-ylidene)-1-phenylethan-1-one, was thermodynamically most stable, the results of MP2 ab initio calculations reveal the following order of stability: ketimine > enolimine > enaminone (substituents do not affect this sequence). 13C CPMAS NMR spectral data reveal that in the crystalline state the enolimine tautomer O is predominant in the p-CH3 and p-NO2 substituted congeners.

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2-苯基苯并咪唑溶液中的互变异构平衡

对取代的2-苯并咪唑(氯胺酮形式，K)的DMSO-d6溶液进行了详细的核磁共振光谱分析，揭示了三种互变异构形式中的两种。利用1H NMR信号的积分来确定互变异构体的摩尔比。实验分析得到了量子化学计算的支持，令人满意地再现了实验趋势。尽管已有的半经验量子化学计算表明，2-(1,3-二氢- 2h -苯并[d]咪唑-2-乙基二烯基)-1-苯基比-1- 1是热力学上最稳定的，但MP2从头计算的结果显示，其稳定性顺序如下:氯胺酮>烯丙胺>胺酮(取代基不影响该顺序)。13C - CPMAS NMR数据显示，在结晶状态下，p-CH3和p-NO2取代的同系物中，烯丙胺互变异构体O占主导地位。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Heteroatom Chemistry 化学-化学综合

CiteScore

1.20

自引率

0.00%

发文量

审稿时长

6 months

期刊介绍： Heteroatom Chemistry brings together a broad, interdisciplinary group of chemists who work with compounds containing main-group elements of groups 13 through 17 of the Periodic Table, and certain other related elements. The fundamental reactivity under investigation should, in all cases, be concentrated about the heteroatoms. It does not matter whether the compounds being studied are acyclic or cyclic; saturated or unsaturated; monomeric, polymeric or solid state in nature; inorganic, organic, or naturally occurring, so long as the heteroatom is playing an essential role. Computational, experimental, and combined studies are equally welcome. Subject areas include (but are by no means limited to): -Reactivity about heteroatoms for accessing new products or synthetic pathways -Unusual valency main-group element compounds and their properties -Highly strained (e.g. bridged) main-group element compounds and their properties -Photochemical or thermal cleavage of heteroatom bonds and the resulting reactivity -Uncommon and structurally interesting heteroatom-containing species (including those containing multiple bonds and catenation) -Stereochemistry of compounds due to the presence of heteroatoms -Neighboring group effects of heteroatoms on the properties of compounds -Main-group element compounds as analogues of transition metal compounds -Variations and new results from established and named reactions (including Wittig, Kabachnik–Fields, Pudovik, Arbuzov, Hirao, and Mitsunobu) -Catalysis and green syntheses enabled by heteroatoms and their chemistry -Applications of compounds where the heteroatom plays a critical role. In addition to original research articles on heteroatom chemistry, the journal welcomes focused review articles that examine the state of the art, identify emerging trends, and suggest future directions for developing fields.