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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/12903

Title: Quantum chemical studies on the mechanistic aspects of tandem sequential cycloaddition reactions of cyclooctatetraene with ester and nitrones
Authors: Opoku, Ernest
Tia, Richard
Adei, Evans
Keywords: Isoxazolidines
Mechanistic study
Tandem addition
Issue Date: 5-Jul-2019
Publisher: Elsevier Inc.
Abstract: The mechanisms of the tandem sequential [4 þ 2]/[3 þ 2] and [3 þ 2]/[4 þ 2] cycloaddition sequences involving an ester, cyclooctatetraene (COTE), and cyclic and acyclic nitrones for the formation of a diverse range of isoxazolidine derivatives and other synthetic precursors are reported. A thorough exploration of the PES has characterized several regio-, stereo- and enantio-selective mechanistic channels involved in these reactions. A perturbation molecular orbital (PMO) analysis been employed to rationalize the results. It has also been found that the initial electrocyclic ring closure of the COTE is the rate-determining step in the tandem sequential [4 þ 2]/[3 þ 2] addition sequence. The thermolytic breakdown of the tandem adducts to subsequent monocyclic, bicyclic and tricyclic adducts occurs generally with very high activation barriers making it an inconvenient synthetic approach. The different reactivity of all the three double bonds present in the dipolarophile is reported. Finally, the mechanistic possibilities of [3 þ 2]/ [4 þ 2] addition sequences involving the same reaction components in the case of cyclic and acyclic nitrones are explored extensively. The results suggest a novel and convenient routes for obtaining products of high selectivity with less energetic requirements. In some instances, new cycloadducts hitherto unreported are obtained.
Description: An article published by Elsevier Inc. and also available at https://doi.org/10.1016/j.jmgm.2019.06.019
URI: http://hdl.handle.net/123456789/12903
Appears in Collections:College of Science

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