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Unveiling the Role of the Strain of Cyclohexyne in [3+2] Cycloaddition Reactions through the Molecular Electron Density Theory

Abstract

The [3+2] cycloaddition (32CA) reactions of cyclohexyne (SCH), a cyclic strained acetylene, with methyl azide and methoxycarbonyl diazomethane have been studied within the Molecular Electron Density Theory (MEDT) at the DFT MPWB1K/6-311G(d) computational level. These 32CA reactions, which take place through a one-step mechanism involving highly asynchronous transition state structures, proceed with relatively low activation energies of 7.5 and 4.2 kcalĀ·mol-1, respectively, both reactions being strongly exothermic. The reactions are initiated by the creation of a pseudoradical center at one of the two acetylenic carbons of SCH with a very low energy cost, which promotes the easy formation of the first C-N(C) single bond in the adjacent acetylenic carbon. This scenario is completely different from that of the 32CA reaction involving non-strained but-2-yne; thus, strain changes both the electronic structure and the reactivity of SCH. Finally, the experimental regioselectivity of the 32CA reactions involving 3-alcoxy SCH derivatives is correctly explained within MEDT.

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Publication details

The article was received on 16 Oct 2018, accepted on 04 Dec 2018 and first published on 04 Dec 2018


Article type: Paper
DOI: 10.1039/C8OB02568A
Citation: Org. Biomol. Chem., 2018, Accepted Manuscript
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    Unveiling the Role of the Strain of Cyclohexyne in [3+2] Cycloaddition Reactions through the Molecular Electron Density Theory

    L. R. Domingo, M. Rios-Gutierrez and P. Perez, Org. Biomol. Chem., 2018, Accepted Manuscript , DOI: 10.1039/C8OB02568A

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