Synthesis and molecular assembly of benzenoid ring-mounted U-shaped septuple-bridged [7,7]orthocyclophanes walled by cofacial quinoxaline rings

摘要

The U-shaped septuple-bridged [7,7]orthocyclophanes (10Aa-c and 10Ca-c), side-walled with cofacial quinoxaline (QX) and benzoquinoxalinedione (BQXO) rings and mounted with N-(anthracen-9-ylmethyl)-, N-(naphthalen-2-ylmethyl)-, and N-(pyren-l-ylmethyl)succinimide ring, were, respectively, synthesized from the corresponding N-(4-methoxybenzyl)succinimide ring-incorporated, QX and benzoquinoxaline (BQX) ring-walled analogues molecular systems (1A and 1B). The synthesis involved oxidative removal of N-(4-methoxybenzyl) group from 1A and 1B with ceric ammonium nitrate (CAN), followed by Gabriel-type N-alkylation with a proper arylmethyl bromide. The BQX ring in 113 was found to be oxidized to BQXO ring in the CAN-oxidation step. The molecular cleft-like [7,7]orthocyclophanes thus synthesized display a tendency of self-assembly chiefly driven by intermolecular pi-pi stacking interaction, forming V-shaped or linear tail-to-tail (wall-to-wall) dimers that further assemble in head-to-head (aryl-to-aryl) arrangement to form tetramers and polymers. The event of molecular assembly was investigated by concentration-variant H-1 NMR spectroscopic and X-ray crystallographic analyses. (C) 2015 Elsevier Ltd. All rights reserved.