title: Tribenzotriquinacenes based on regioselective bis-formylation: optical resolution and absolute configuration of inherently chiral derivatives and synthesis of the first cyclophane-type tribenzotriquinacene dimers.
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 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.
authors.affiliation: State Key Laboratory of Applied Organic Chemistry and College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, P. R. China.
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
authors.forename: Qin-Qing
authors.initials: QQ
authors.lastname: Hou
authors.forename: Qing-Feng
authors.initials: QF
authors.lastname: Teng
authors.forename: Xiao-Jun
authors.initials: XJ
authors.lastname: Yao
authors.forename: Wen-Xue
authors.initials: WX
authors.lastname: Niu
authors.forename: Xiao-Ping
authors.initials: XP
authors.lastname: Cao
authors.forename: Dietmar
authors.initials: D
authors.lastname: Kuck