1. Regioselective amination of 4-methylene-5,7-dinitroquinazoline: a mechanistic consideration on non-conventional N-H—π interactions between amine and ethylene moiety.
- Author
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Singh, Amritpal, Chayawan, Chayawan, Deol, Yadwinder Singh, Kumar, Santosh, Kumar, Rajesh, and Mittal, Lalit Singh
- Subjects
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AMINATION , *GIBBS' energy diagram , *HYDROGEN bonding interactions , *ETHYLENE , *MOIETIES (Chemistry) , *AMINES - Abstract
Pi (π) interactions originating from the N-H bond of amine and ethylene moiety have been explored on the mechanism of aromatic nucleophilic substitution (ArSN) of the nitro group of 4-methylene-5,7-dinitroquinazoline with methylamine in the gas phase and solvent media within DFT framework. The free energy profiles confirmed that the amination should take place at peri-position and calculations support the one-step mechanism through a transition state with no intermediate in the reaction route. Stabilisation of peri-transition state by intramolecular weak interaction akin to hydrogen bonding N-H—CH2 = C leads to the regioselective amination at peri-position of 4-methylene-5,7-dinitroquinazoline. The intramolecular hydrogen bond interactions at N-H—CH2 = C in the peri-transition state are strongly supported by a red shift in N-H stretching vibrations in simulated IR spectra and are confirmed by studying energetics of amination of structural/electronic analogues of 4-methylene-5,7-dinitroquinazoline. The present study established that ethylene plays an important role as an efficient H-bond acceptor in fixing the regioselectivity at peri-position in the amination of 4-methylene-5,7-dinitroquinazoline. This is the first-ever report for the exploration of the role of ethylene moiety as a hydrogen bond acceptor in mediating the regioselectivity of organic reactions. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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