BISACETALS OF AROMATIC RING-ANNELATED BENZO[A,D]BIS(BICYCLO[4.4.1]UNDECA3,8-DIENE-11-ONE) - [3.3][3.3]ORTHOCYCLOPHANES WITH TRIPLE-LAYERED BENZO/BENZO/BENZO- AND NAPHTHO/BENZO/NAPHTHO-SYSTEM

摘要

Tetraesters anti-9a,b and syn-9a,b, which have three aromatic rings, were prepared by the reaction of benzocycloheptenediester 7 with 1,2,4,5-tetrakis(bromomethyl)benzene. Subsequent hydrolysis and pyrolysis gave diketones anti-11a,b and syn-11a,b, which were acetalized to yield bisacetals anti-5a,b and syn-5a,b. X-Ray crystallographic analyses indicate a symmetric (twin-chair)/(twin-chair)-conformation of anti-5a,b, in which two naphtho or benzo rings sandwich one benzene ring. Anti-5a and anti-5b(9b)) are rigid structures. The protons of their central aromatic rings show an up-field shift, due to an anisotropic effect of the facing outer aromatic units. In contrast, syn-5a,b are flexible structures. The UV-spectra of anti-5a,b show a long wavelength shift, as compared to syn-5a,b, suggesting a through-space interaction among the aromatic rings. (C) 1997 Elsevier Science Ltd. [References: 19]