Monoaryne and monoisobenzofuran analogues of a C(3v)-symmetrical tribenzotriquinacene (TBTQ) were generated in situ and trapped with various dienes and dienophiles, respectively. In this way, a series of single-wing extended TBTQ derivatives bearing the bowl-shaped TBTQ unit in different topographical expositions have become accessible. This includes some novel tribenzotriquinacene "dimers", in which two TBTQ bowls are attached in syn- or anti-orientation at the terminal positions of rigid linker units. Several of these compounds have been characterized by both spectroscopy and X-ray structural analysis. The efficient access to the TBTQ "dimers" may lay a useful foundation for further studies of novel container compounds and supramolecular architectures.
The synthesis of several inherently chiral tribenzotriquinacenes (TBTQs) bearing one single mono- or difunctionalized aromatic nucleus and the optical resolution of one of these derivatives, a TBTQ-based salicylic acid (11), are described for the first time. Efficient access to enantiopure, inherently chiral tribenzotriquinacenes may lay a foundation for studies of novel container compounds, supramolecular aggregation, chiral recognition, and asymmetric catalysis.
Enantiomerically pure tribenzotriquinacenes (TBTQs) bearing two monofunctionalized aromatic nuclei were synthesized for the first time and their optical properties and absolute configuration determined. A remarkably regioselective bis-formylation of the fully bridgehead methylated parent TBTQ hydrocarbon with MeOCHCl(2)/TiCl(4) afforded a mixture of two C(s)-symmetrical (achiral) difunctionalized derivatives together with one C(1)-symmetrical (chiral) isomer. Reduction and subsequent column chromatography furnished the three respective benzylic TBTQ dialcohols. Optical resolution of the racemic 2,6-bis(hydroxymethyl) derivative was achieved via the diastereomeric (R)-1,1'-bi-2-naphthol ethers and the absolute configuration of the enantiomers was determined by CD exciton model analysis. The electronic circular dichroism (ECD) spectra and the specific rotation of the enantiomers were found to agree with the results of DFT calculations. Among the C(s)-symmetrical isomers, the "proximal" 2,11-dialdehyde and the corresponding benzylic dialcohol were identified by 2D NMR spectroscopy and X-ray crystallographic analysis, respectively, and used as the starting point for the synthesis of several novel dithiametacyclophanes. These include the first "dimeric" tribenzotriquinacene-based cyclophanes bearing the bowls of the two TBTQ units attached to each other in a syn (concave-concave) or anti (convex-concave) configuration. The usefulness of such thiacyclophanes as fluorescent chemosensors for different metal ions is also demonstrated.
An enantioselective selenolactonization of olefinic acids has been developed using (DHQD)2PHAL as the catalyst. Structurally simple and commercially available N-phenylselenophthalimide was used as the electrophilic selenium reagent. The corresponding selenolactones could be obtained with up to 96% ee.
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