Unveiling the mechanism and selectivity of [3+2] cycloaddition reactions of benzonitrile oxide to ethyl trans -cinnamate
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ORIGINAL PAPER
Unveiling the mechanism and selectivity of [3+2] cycloaddition reactions of benzonitrile oxide to ethyl trans-cinnamate, ethyl crotonate and trans-2-penten-1-ol through DFT analysis Khalid Abbiche 1,2 & Nivedita Acharjee 3 Najia Komiha 5 & Khadija Marakchi 5
&
Mohammed Salah 4 & Mustapha Hilali 1 & Abdelatif Laknifli 2 &
Received: 7 August 2020 / Accepted: 14 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The mechanism and regioselectivity of [3+2] cycloaddition (32CA) reactions of benzonitrile oxide with ethyl trans-cinnamate, ethyl crotonate and trans-2-penten-1-ol has been studied in gas phase and in acetonitrile, ethyl acetate and tetrahydrofuran using the B3LYP functional in connection with 6-31G(d) basis set. The 32CA reactions followed one-step mechanism with asynchronous TSs. The calculated global electron density transfer (GEDT) at the TSs showed electronic flux from benzonitrile oxide to ethyl trans-cinnamate and ethyl crotonate, while the electronic flux from trans-2-penten-1-ol to benzonitrile oxide was predicted, in complete agreement with the Conceptual Density Functional Theory (CDFT) indices. The regioselectivity is correctly described in coherence with the experiment data. The intermolecular interaction at the TSs was realized through visualization and quantification by means of independent gradient model (IGM) analysis based on promolecular density. Keywords Benzonitrile oxide . Ethyl trans-cinnamate . Ethyl crotonate . trans-2-penten-1-ol . Density functional theory . Independent gradient model
Introduction [3+2] cycloaddition (32CA) reactions of nitrile oxides with alkene and alkyne derivatives yield wide range of fivemembered heterocycles isoxazoles, isoxazolines, oxadiazoles, oxadiazolines and dioxazolidines of synthetic and biological importance [1–3]. In particular, the 32 CA reactions of nitrile oxides to alkenes is a useful method to generate isoxazolines,
which are versatile intermediates for the synthesis of a large variety of complex natural products [4–6]. The 32CA reactions between nitrile oxides and alkenes can proceed along two regiochemical reaction paths leading to 4-isoxazoline and 5-isoxazoline derivatives [7] (see Scheme 1). The mechanism of 32CA reactions of nitrile oxides with alkenes has been the object of several investigations since the last four decades [8–11]. Beside a one-step mechanism [8, 9],
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00894-020-04547-6) contains supplementary material, which is available to authorized users. * Khalid Abbiche [email protected] * Nivedita Acharjee [email protected] 1
2
Applied Chemistry-Physics and Environment Team, Faculty of Sciences, Ibn Zohr University, B. P. 8106 Cité Dakhla, Agadir, Morocco Polydisciplinary Faculty of Taroudant, Ibn Zohr University, Hay El Mohammadi (Lastah), BP. 271, 83000 Taroudant, Morocco
3
Department of Chemistry, Durgapur Government College, Durgapur, Paschim Bardhaman, West Bengal 713214, Ind
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