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Title: Mechanistic study of the tandem intramolecular (4 + 2)/intermolecular (3 + 2) cycloaddition reactions for theformation of polyaza- and polyisoxazolidine-steroids
Authors: Opoku, Ernest
Pipim, George Baffour
Tia, Richard
Adei, Evans
Issue Date: 2-Jan-2020
Publisher: John Wiley & Sons, Inc.
Citation: Opoku E, BaffourPipim G, Tia R, Adei E. Mechanistic study of thetandem intramolecular (4 + 2)/intermolecular(3 + 2) cycloaddition reactions for the formation ofpolyaza- and polyisoxazolidine-steroids.JHeterocyclic Chem. 2020;57:1748–1758.https://doi.org/10.1002/jhet.3900
Abstract: The ability to construct molecules with potential applications in biomedicinevia efficient and selective molecular design and syntheses hinges on a thor-ough understanding of underlying reaction mechanisms. The biological impor-tance of steroids and related heterocyclic compounds are well known buttheoretical studies aimed at delineating reaction mechanisms to complementefforts of experimentalists are lacking. Herein, we report an extensive theoreti-cal study on the regio-, stereo-, and enantio-selectivity of the tandem sequen-tial intramolecular (4 + 2)/intermolecular (3 + 2) cycloaddition reaction of(E)-3-(2-[furan-2-ylmethoxy]phenyl)acrylate derivatives (R1) and azides (R3andR30) as well as nitrones (R2) for the formation of steroids. In the reactionofR1and the azide derivativesR3andR30, the intramolecular (4 + 2) cycload-dition ofR1is the rate-determining step (rds). The reaction is also found to bevery selective. Reaction of electron-withdrawing groups-substitutedR1withR3is found to generally increase the barrier of the rds except bromine whileselectron-donating groups are found to generally decrease the activation ener-gies of the rds. Subsequently, we report a novel reaction ofR1with cyclicnitrone (R2), which compares favorably with the azide reaction. Results fromthe global reactivity descriptors are in good agreement with the activation bar-rier trends. All the considered reactions in this study are found to be kineti-cally driven.
Description: An article published by John Wiley & Sons, Inc. and also available at https://doi.org/10.1002/jhet.3900
URI: http://hdl.handle.net/123456789/12680
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