Medium-sized cyclophanes. Part XIX. Bridged naphthalenes: structural aspects, carbon-13 nuclear magnetic resonance, and benzoperylene formation

Abstract

‘cis’-[2.2](2,7)Naphthalenophane has been isolated from the reaction of 2,7-bisbromomethylnaphthalene with sodium. The structure was assigned by comparing the spectra with those of Baker's ‘trans’-compound and acyclic models. The carbon-13 n.m.r. spectrum revealed an anomalous downfield shift of the inner aryl carbon resonances for the ‘trans’-compound as compared with the ‘cis’-isomer. This was attributed to p orbital compression. The attempted preparation of an extremely distorted bridged αα′-binaphthyl, [2.0](7,1)naphthalenophane, by the Wurtz reaction gave dehydrogenation products (benzoperylenes). The homologue incorporating a sulphur atom in a three-membered bridge, 3-thia[3.0](7,1)naphthalenophane, has a rigid structure with considerable strain as evidenced by u.v. and n.m.r. spectra.