Next Article in Journal
A Novel Framework Using Neutrosophy for Integrated Speech and Text Sentiment Analysis
Previous Article in Journal
Numerical Investigations on Magnetohydrodynamic Pump Based Microchannel Cooling System for Heat Dissipating Element
Open AccessFeature PaperArticle

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
*
Author to whom correspondence should be addressed.
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 Special Issue Symmetry-Asymmetry 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
Show Figures

Figure 1

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.

Show more citation formats Show less citations formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Search more from Scilit
 
Search
Back to TopTop