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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/12659

Title: Site‑, enantio‑ and stereo‑selectivities of the 1,3‑dipolar cycloaddition reactions of oxanorbornadiene with C,N‑disubstituted nitrones and dimethyl nitrilimines: a DFT mechanistic study
Authors: Opoku, Ernest
Arhin, Grace
Pipim, George Baffour
Adams, Anita Houston
Tia, Richard
et. al
Keywords: Dipole
Oxanorbornadiene
Nitrone
Enantioselectivity
Density functional theory
Issue Date: 1-Jan-2020
Publisher: Springer-Verlag GmbH Germany
Citation: Theoretical Chemistry Accounts (2020) 139:16 https://doi.org/10.1007/s00214-019-2529-8
Abstract: 1,3-Dipolar cycloaddition of nitrones to oxanorbornadienes is an important method for the enantioselective synthesis of highly substituted 5-membered heterocycles such as furans and isoxazolidines, which have high utility in the chemical and pharmaceutical industries. The mechanism of the reaction and the effects of substituents on the (3 + 2) cycloaddition reactions (32CA) of C,N-dialkyl nitrones with a series of substituted oxanorbornadienes have been studied with focus on the site-selectivity (attack on the more substituted double bond of the oxanorbornadiene derivatives versus attack on the less substituted double bond), enantioselectivity and stereo-selectivity using density functional theory calculations at the M06/6-311++G(d,p) of theory. The results showed that the addition step to form the bicyclic isoxazolidines cycloadducts has generally low barriers compared to the cycloreversion step which converts the cycloadducts into furans and monocyclic isoxazolidines. Generally, electron-withdrawing substituents favour the nitrone attack on the highly substituted double bond, while electron-donating substituents favour the attack on less substituted double bond. The R enantiomers are generally favoured over the S enantiomers, and exo stereo-isomers are generally favoured over the endo stereo-isomers, irrespective of substituents.
Description: An article published by Springer-Verlag GmbH Germany and also available at https://doi.org/10.1007/s00214-019-2529-8
URI: http://hdl.handle.net/123456789/12659
Appears in Collections:College of Science

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