Tribenzotriquinacenes Based on Regioselective Bis‐formylation: Optical Resolution and Absolute Configuration of Inherently Chiral Derivatives and Synthesis of the First Cyclophane‐Type Tribenzotriquinacene Dimers |
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Authors: | Tao Wang Qin‐Qing Hou Qing‐Feng Teng Xiao‐Jun Yao Wen‐Xue Niu Prof Xiao‐Ping Cao Prof Dietmar Kuck |
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Institution: | 1. State Key Laboratory of Applied Organic Chemistry and College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, P. R. (China), Fax: (+86)?931‐8912582;2. Department of Chemistry, Bielefeld University, Universit?tsstra?e 25, 33615 Bielefeld (Germany), Fax: (+49)?521‐1066417 |
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Abstract: | 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 MeOCHCl2/TiCl4 afforded a mixture of two Cs‐symmetrical (achiral) difunctionalized derivatives together with one C1‐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 Cs‐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. |
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Keywords: | configuration determination formylation regioselectivity synthetic methods tribenzotriquinacenes |
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