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The thermal treatment of abietane skeleton diterpenoids yields a number of mono-, di- and tri-aromatic hydrocarbons. The aromatization process follows the thermal constraint and the degree of aromatization is higher with higher operating temperature. It seems possible to correlate the composition pitches with the thermal treatments specially those, which were used in Antic production sites. During the aromatization process, the retene, which is formed, is demethylated to give the 7-ethyl-1-methylphenanthrene and then the 1,7-dimethylphenanthrene. In the mean time, the retene is also methylated and gives methylretenes (MR) and dimethylretenes (DMR).The semi-empirical AM1/RHF method has been used to calculate local minimum structures of ∼60 retene-like molecules together with their relative enthalpies of formation. This study allows to correlate the calculated geometries and the stabilities and to link the thermodynamic properties and shapes of individual isomers with their relative abundance during thermal degradation. [Copyright &y& Elsevier]

Designed as a multivalent hydrogen bond acceptor, new receptors, Discopus 1a,b, were built from a triphenylene core surrounded by six (diaryl)phosphinate groups. An efficient synthesis was developed to prepare these elaborated structures in a high overall yield. The X-ray structure of receptor 1b showed strong cooperative hydrogen bonds with two water molecules and intermolecular CH-π contacts. In chloroform, Discopus la,b displayed recognition properties toward dihydroxybenzenes, selectively forming complexes with catechol derivatives 4a-c in a 1:2 (host:guest) stoichiometry. According to NMR and microcalorimetry titrations, association constants were found in the 30-2837 M-1 range, which were larger than those reported for curvated catechol receptors (14-120 M-1). Interestingly, Discopus present two distinct catechol binding sites. Weak hydrogen bonding between host phosphinates and guest hydroxyl groups was shown by infrared spectroscopy and 31P NMR. Molecular dynamics simulations and recognition experiments suggested that a stronger hydrogen bond assisted by a π-interaction between the Discopus core and one catechol molecule could exist within the 1:2 complex. [ABSTRACT FROM AUTHOR]