Synthesis of Rigid Receptors Based on Triphenylene Ketals

Abstract

The synthesis of rigid receptors based on triphenylene ketals, including some improved procedures, is described in detail. Since chemical transformations are strongly influenced by the rigid character and steric bulkiness of the receptors, the construction of a subunit allowing quicker synthetic development is also reported. The preparation of these receptor structures involves an oxidative trimerization and a subsequent repeated isomerization procedure. The scope for the attachment of sterically demanding affinity groups on the receptor scaffold and the corresponding subunit is discussed, and the molecular structures and available space for molecular recognition of the chirally modified systems are outlined by some crystal structures. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Stereoselective Formation of Triphenylene Ketals

“…R f = 0. 13 2, 24.5, 31.3, 40.4, 42.2, 106.5, 107.0, 112.6, 120.7, 123.6, 137.5, 147.8, 149.1, 158.6 Compound I: A solution of nitrile 5 e (0.5 g, 2.2 mmol) in ethanol (10 mL) was treated with a 10 % aqueous solution of NaOH (5 mL). The reaction mixture was heated at reflux for 17 h before the mixture was diluted with H 2 O (50 mL).…”

“…A repetitive sequence of isomer separation and isomerization under strong acidic conditions allows the formation of larger quantities of the all-syn functionalized triphenylene ketal. [13] A more efficient approach to these compounds would facilitate access to these platforms and promote their application. Herein, we report a stereoselective formation of triphenylene ketals by the action of MoCl 5 or MoCl 5 /TiCl 4 mixtures.…”

“…[10] Triphenylene ketals represent triketals of 2,3,6,7,10,11-hexahydroxytriphenylene and can be synthesized by oxidative trimerization of the corresponding catechol ketals, employing MoCl 5 [11] or anodic protocols. [12,13] If functionalized benzoA C H T U N G T R E N N U N G [1,3]dioxols are subjected to these methods, the statistical mixture is produced, yielding more than 75 % of the undesired stereoisomer. A repetitive sequence of isomer separation and isomerization under strong acidic conditions allows the formation of larger quantities of the all-syn functionalized triphenylene ketal.…”

Extraction of Radio‐Labelled Xanthine Derivatives by Artificial Receptors: Deep Insight into the Association Behaviour

“…Triphenylene ketals with a rigid backbone were synthesised in a ten-step sequence that has been described previously. [15] The final, divergent transformation involves treating the triamino platform 5 with the appropriate isocyanates so as to generate the corresponding threefold functionalised systems 1 bearing urea moieties (Scheme 2, Table 1). The more flexible, and therefore less pre-organised host molecules 7 were obtained by a similar sequence.…”

“…The preparation of chiral receptors 1 e-1 h, based on the rigid platform, has been described in detail elsewhere. [9,15] To underline the importance of appropriately arranged multiple binding sites, a corresponding subunit 8 of 1 c was prepared as previously reported and was also employed in the affinity testing. [15] Applying the synthetic protocol to the more flexible platform 6 yielded the host molecules 7, which are less lipophilic than the rigid congeners (Scheme 2).…”