Insights into the mechanism and regiochemistry of the 1,3-dipolar cycloaddition reaction between benzaldehyde and diazom
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Insights into the mechanism and regiochemistry of the 1,3‑dipolar cycloaddition reaction between benzaldehyde and diazomethane K. Abbiche1,2 · H. Mohammad‑Salim3 · M. Salah4 · N. Mazoir5 · A. Zeroual4 · H. El Alaoui El Abdallaoui4 · A. El Hammadi2 · M. Hilali1 · H. H. Abdallah6 · M. Hochlaf7 Received: 6 July 2020 / Accepted: 5 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The 1,3-dipolar cycloaddition reaction of benzaldehyde with diazomethane is investigated, in gas phase and in diverse polar solvents, using the molecular electron density theory through density functional theory calculations at the B3LYP(+D3)/631G(d) level. Analysis of the reaction pathway reveals that this reaction takes place along a concerted but asynchronous mechanism. Computations show that the acetophenone product is kinetically and thermodynamically more favored than 2-phenylacetaldehyde product in agreement with experimental outcomes. The favored cyclization mode and the observed regioselectivity of this cycloaddition are rationalized by both activation energy calculations, frontier molecular orbital analysis and reactivity indices. Also, polar solvents effect favors the reaction. Furthermore, we performed electron localization function (ELF) topological analysis. The ELF topological analysis of diazomethane indicates that this reactant presents an allenic pseudoradical electronic structure. Keywords Diazomethane · Benzaldehyde · DFT/B3LYP-D3 · Regioselectivity · Cycloaddition reaction · MEDT · ELF
1 Introduction 1,3-Dipolar cycloaddition reactions play an important role in organic chemistry [1]. Indeed, they are routes for the synthesis of a large variety of functionalized five-membered heterocyclic systems, which in turn often lend themselves as ideal synthons of “non heterocyclic” derivatives [2]. The influence of the 1,3-dipolar cycloaddition reactions in the Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00214-020-02662-4) contains supplementary material, which is available to authorized users. * K. Abbiche [email protected] * M. Hochlaf hochlaf@univ‑mlv.fr 1
Applied Chemistry‑Physics and Environment Team, Faculty of Sciences, Ibn Zohr University, Cité Dakhla, B.P. 8106, Agadir, Morocco
2
Polydisciplinary Faculty of Taroudant, Ibn Zohr University, Hay El Mohammadi (Lastah), B.P. 271, 83000 Taroudant, Morocco
3
Department of Chemistry, Faculty of Science, University of Zakho, Duhok, Iraq
field of heterocyclic synthesis is in many ways comparable to that of Diels–Alder reactions on carbocyclic synthesis [3]. In fact, the availability of various classes of dipoles and dipolarophiles has allowed many perspectives. The earlier works of Huisgen and coworkers [4–8] revealed that the mechanism of 1,3-dipolar cycloadditions leading to 5-membered rings is governed by the stereoselectivity of dipolarophiles, by the nature of solvent and substituents, by the activation parameters and by orientation phenomena. Since then, 1,3-
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