Supramolecular diversity of oxabicyclo[2.2.2]octenes formed between substituted 2H-pyran-2-ones and vinyl-moiety-containing dienophiles

Krištof Kranjc (Author), Amadej Juranovič (Author), Marijan Kočevar (Author), Franc Perdih (Author)

Abstract

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 CO$_2$-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 CO$_2$ 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.

Keywords

Diels-Alderjeva reakcija;organska sinteza;heterocikli;vodikova vez;kristalna struktura;Diels-Alder reaction;organic synthesis;heterocycles;hydrogen bonds;crystal structure;

Data

Language:	English
Year of publishing:	2020
Typology:	1.01 - Original Scientific Article
Organization:	UL FKKT - Faculty of Chemistry and Chemical Technology
UDC:	547.81:547.72
COBISS:	33257219
ISSN:	2073-8994
Views:	179
Downloads:	54
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	Slovenian
Secondary keywords:	Diels-Alderjeva reakcija;organska sinteza;heterocikli;vodikova vez;kristalna struktura;
Type (COBISS):	Article
Pages:	str. 1-23
Volume:	ǂVol. ǂ12
Issue:	ǂiss. ǂ10
Chronology:	Oct. 2020
DOI:	10.3390/sym12101714
ID:	14373098