EVALUATION OF THROUGH-SPACE INTERACTION IN [2.2]METACYCLOPHANES BY DIAZO COUPLING REACTION

An azobenzene moiety was introduced into various [2.2]metacyclophanes (MCPs) 1 via diazo coupling reactions. The functional groups on the in ner (8,16-) or outer (13-) positions affect the reactivity of the oute r (5-) position toward the diazonium salts to a large extent. It was a lso observed that one aromatic ring of [2.2]MCPs can be subject to att ack of diazonium salts very easily; however, the other aromatic ring n ever undergoes attack. The electronic absorption wavelengths of the az o[2.2]MCPs are bathochromically shifted from those of model reference compounds. When the lambda(max)-values of azo[2.2]MCPs which carry a f unctional group on the outer (13-) position are plotted against the su bstituent's Hammett contstants (sigma(p)), a straight line is obtained . These results established that the electronic effect of the function al group is transmittable between the two aromatic rings in [2.2]MCPs by a through-space interaction.