Medium-sized cyclophanes. Part XIV. An aromatic displacement reaction in veratrylic compounds. Attempted nitration and halogenation of cyclotriveratrylene (10,15-dihydro-2,3,7,8,12,13-hexamethoxy-5H-tri-benzo[a,d,g]cyclononene)

Abstract

On nitration and halogenation cyclotriveratrylene did not give nuclear substituted derivatives but gave ring cleavage products in which a veratryl group was replaced by an electrophile. The cleavage reaction was shown to occur in a stepwise manner. Under controlled conditions o-dibenzylbenzenes such as (III)—(V), (X)—(XIII), and (XVI) were obtained in high yield and were further cleaved to diphenylmethane derivatives [(VI) and (XIV)] and veratrole derivatives [(VII), (VIII), and 4,5-dibromoveratrole]. Cleavage is facilitated because there is (a) high electron density para to a methoxy-group for electrophilic attack and (b) stabilization of the veratryl cation as a good leaving group. The tribenzocyclononene ring system is not inherently responsible for the cleavage.