Conformational changes in bridged anthracene and tetracene systems

Abstract

The n.m.r. spectra of 9,10-endo-(NN′-dimethoxy- and -ethoxy-carbonylhydrazo)-9,10-dihydroanthracene and 5,12-endo-(NN′-dimethoxycarbonylhydrazo)-5,12-dihydrotetracene show temperature dependence which may be associated with conformational changes involving hindered rotation about the N–CO₂R bonds and a process involving non-planarity of the diacylhydrazine system. These results are discussed in relation to the previously observed hindered ring inversion of NN′-diacyltetrahydropyridazines.