Modelling of Transition State in Grignard Reaction of Rigid N-(Aryl)imino-Acenapthenone (Ar-BIAO): A Combined Experimental and Computational Study

Anga, S and Gupta, S D and Rej, S and Mallik, Bhabani Shankar and Panda, Tarun K (2014) Modelling of Transition State in Grignard Reaction of Rigid N-(Aryl)imino-Acenapthenone (Ar-BIAO): A Combined Experimental and Computational Study. Australian Journal of Chemistry, 68 (6). pp. 931-938. ISSN 0004-9425

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Abstract

We present a combined synthetic and computational study on the addition of Grignard reagents RMgBr/RMgI (R = Me, Et) to various sterically rigid N-(aryl)imino-acenapthenone (Ar-BIAO) (Ar = 2,6-iPr2C6H3 (1), 2,6-Me2C6H3 (2), and 2,4,6-Me3C6H2 (3) ligands). In the experimental method, when compounds 1–3 were treated with RMgBr (R = Me, Et) at room temperature, the corresponding racemic N-(aryl)imino-acenapthylene-1-ol (Ar-BIAOH) compounds (Ar = 2,6- iPr2C6H3, R = Me (1a), Et (1b); Ar = 2,6-Me2C6H3, R = Me (2a), Et (2b); and Ar = 2,4,6-Me3C6H2, R = Me (3a), Et (3b)) were obtained in yields up to 82 %. The Ar-BIAOH compounds were characterized by spectroscopic and combustion analyses. The solid state structures of compounds 1a–3a were established by single-crystal X-ray diffraction analysis. To model the transition state of the Grignard reaction with asymmetrical and sterically rigid Ar-BIAO ligands having three fused rings containing exo-cyclic carbonyl and imine functionalities, we carried out computational analysis. During our study, we have considered the gas phase addition of CH3MgBr to 2 and the model system of 2-(methylimino)pentanone (2′). We have carried out ab initio (HF/3–21G*) and density functional theory calculations with the hybrid density functional B3LYP/6–311+G(2d,p) to probe two major aspects: (1) the stability of an intra-molecular chelation involving magnesium, carbonyl oxygen, and imine nitrogen and (2) to suggest a probable transition state and a mechanistic pathway. The computational investigation suggests the formation of a tetra-coordinated magnesium complex as the transition state for the Grignard reaction.

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IITH Creators:
IITH CreatorsORCiD
Mallik, Bhabani Shankarhttp://orcid.org/0000-0001-9657-1497
Panda, Tarun Khttp://orcid.org/0000-0003-0975-0118
Item Type: Article
Subjects: Chemistry
Divisions: Department of Chemistry
Depositing User: Team Library
Date Deposited: 31 Jul 2015 09:57
Last Modified: 07 Sep 2017 10:55
URI: http://raiithold.iith.ac.in/id/eprint/1751
Publisher URL: https://doi.org/10.1071/CH14399
OA policy: http://www.sherpa.ac.uk/romeo/issn/0004-9425/
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