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Article

Supramolecular Diversity of Oxabicyclo[2.2.2]octenes Formed between Substituted 2H-Pyran-2-ones and Vinyl-Moiety-Containing Dienophiles

Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia
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Symmetry 2020, 12(10), 1714; https://doi.org/10.3390/sym12101714
Received: 8 October 2020 / Revised: 12 October 2020 / Accepted: 16 October 2020 / Published: 17 October 2020
(This article belongs to the Collection Feature Papers in Chemistry)
In Diels–Alder reactions, 2H-pyran-2-ones as dienes can yield a large variety of cycloadducts with up to four contiguous carbon stereogenic centers. Some of the potentially most useful, however difficult to prepare due to their low thermal stability, are the primary CO2-containing oxabicyclo[2.2.2]octenes, which could be formed as eight distinctive isomers (two sets of regioisomers, each of these composed of four different stereoisomers). A high-pressure synthesis of such products was recently described in a few cases where vinyl-moiety-containing dienophiles were used as synthetic equivalents of acetylene. However, structures of the primary products have been so far only rarely investigated in detail. Herein, we present seven novel single-crystal X-ray diffraction structures of such cycloadducts of both stereoisomeric forms, i.e., endo and exo. Additionally, we present a single-crystal structure of a rare case of a cyclohexadiene system stable at room temperature, obtained as a secondary product upon the retro-hetero-Diels–Alder elimination of CO2 under thermal conditions (microwave irradiation), during this elimination the symmetry is increased and out of eight initially possible isomers of the reactant, this number in the product is decreased to four. In oxabicyclo[2.2.2]octene compounds, centrosymmetric hydrogen bonding was found to be the predominant motif and diverse supramolecular patterns were observed due to rich variety of C–H⋯O and C–H⋯π interactions. View Full-Text
Keywords: Diels–Alder reaction; X-ray diffraction; organic synthesis; high-pressure conditions; microwave-assisted reactions; heterocycles; hydrogen bonds; aggregation; crystal architecture Diels–Alder reaction; X-ray diffraction; organic synthesis; high-pressure conditions; microwave-assisted reactions; heterocycles; hydrogen bonds; aggregation; crystal architecture
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MDPI and ACS Style

Kranjc, K.; Juranovič, A.; Kočevar, M.; Perdih, F. Supramolecular Diversity of Oxabicyclo[2.2.2]octenes Formed between Substituted 2H-Pyran-2-ones and Vinyl-Moiety-Containing Dienophiles. Symmetry 2020, 12, 1714. https://doi.org/10.3390/sym12101714

AMA Style

Kranjc K, Juranovič A, Kočevar M, Perdih F. Supramolecular Diversity of Oxabicyclo[2.2.2]octenes Formed between Substituted 2H-Pyran-2-ones and Vinyl-Moiety-Containing Dienophiles. Symmetry. 2020; 12(10):1714. https://doi.org/10.3390/sym12101714

Chicago/Turabian Style

Kranjc, Krištof, Amadej Juranovič, Marijan Kočevar, and Franc Perdih. 2020. "Supramolecular Diversity of Oxabicyclo[2.2.2]octenes Formed between Substituted 2H-Pyran-2-ones and Vinyl-Moiety-Containing Dienophiles" Symmetry 12, no. 10: 1714. https://doi.org/10.3390/sym12101714

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