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Mechanisms of the cascade synthesis of substituted 4‐amino‐1,2,4‐triazol‐3‐one from huisgen zwitterion and aldehyde hydrazone: A DFT study
Author(s) -
Zhang Wenjing,
Zhu Yanyan,
Wei Donghui,
Tang Mingsheng
Publication year - 2012
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.22906
Subject(s) - hydrazone , chemistry , zwitterion , aldehyde , density functional theory , computational chemistry , transition state , reaction mechanism , reactivity (psychology) , molecular orbital , nucleophile , medicinal chemistry , molecule , organic chemistry , medicine , alternative medicine , pathology , catalysis
The detailed reaction mechanisms of the title reaction are shed light on by using the density functional theory (DFT). The calculated results have demonstrated that the whole reaction takes place via four processes (processes (I–IV)), among which, three possible reaction mechanisms are proposed for process (II) (channels 1–3) and two for process (IV) (channels 4–5). According to our calculated results, channel 3 and channel 5 are verified to be most energetically favorable. As interpreted in the text, in process (II), the proton transfer should be performed prior to the nucleophilic attack, and the AA‐Type transfer strategy is more likely to occur. The global reactivity index (GRI) and frontier molecular orbital (FMO) analyses of the aldehyde hydrazone have further supported the AA‐Type mechanism. In process (IV), however, the titled product has been demonstrated to be formed by the synergetic elimination of two protons via a six‐membered ring transition state. Taking an integrated view, the highest energy barrier for the whole reaction along the most favorable pathway is 32.19 kcal/mol, which is consistent with the mild thermal experimental conditions. More interestingly, the qualified mechanisms in this work have given a perfect explanation to the optimal reactants molar ratio of highest yields ( R1 / R2 / R3 = 2/1/1) employed in the experiment. © 2012 Wiley Periodicals, Inc.