Gupta, S D
(2014)
Modeling of Transition State in Grignard Reaction of Rigid N-(Aryl)imino-Acenapthenone (Ar-BIAO): An Experimental and Computational Approach.
Masters thesis, Indian Institute of Technology, Hyderabad.
Abstract
In chapter 1, a combined synthetic and computational study has been carried out on the addition
of Grignard reagents RMgBr (R = Me, Et) to various sterically rigid N-(Aryl)imino-
Acenapthenone (Ar-BIAO) (Ar = 2,6-iPr2C6H4 (1), 2,6-Me2C6H4 (2), 2,4,6-Me3C6H3 (3) ligands.
In the experimental method, when the compounds 1-3 were treated with RMgBr (R = Me, Et) in
ambient temperature, the corresponding N-(Aryl)imino-Acenaphthylene-1-ol (Ar-BIAOH) (Ar =
2,6- iPr2C6H4; R = Me (1a), Et (1b); Ar = 2,6-Me2C6H4; R = Me (2a), Et (2b) and Ar = 2,4,6-
Me3C6H3; R = Me (3a), Et (3b) were obtained in a yield up to 82%. The Ar-BIAOH compounds
were characterized by spectroscopic and combustion analyses and the solid state structures of the
compounds 1a-3a were established by single crystal X-ray diffraction analysis. To model the
transition state of the Grignard reaction with unsymmetrical and sterically rigid Ar-BIAO ligands
having three fused rings containing exocyclic carbonyl and imine functionality, we carried out
computational analysis. During our study, we have considered the gas phase addition of
CH3MgBr to 2 (Scheme a) and the model system of 2-(methylimino)pentanone (2′). We have
carried out ab-initio (HF/3-21G(d)) and density functional theory (DFT) calculations with the
hybrid density functional B3LYP/6-311+G(2d,p) to probe into two major aspects (i) stability of
an intra-molecular chelation involving Magnesium, carbonyl Oxygen and imine Nitrogen (ii) to
suggest a probable transition state and mechanistic pathway. The theoretical analysis suggests
the formation of tetra-coordinated magnesium complex as the transition state.
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