Conformational behaviour of medium-sized rings. Part II. Heterocyclic analogues of 5,6,7,12-tetrahydrodibenzo[a,d]cyclo-octene (1,2,4,5-dibenzocyclo-octa-1,4-diene)

Abstract

The temperature dependence of the n.m.r. spectra of a number of heterocyclic analogues (2) of 5,6,7,12-tetrahydrodibenzo[a,d]cyclo-octene has been interpreted in terms of the interconversion of chair- and boat-like conformations. These interpretations have been supported by strain energy calculations, and there is a useful correlation between the activation parameters determined by variable temperature n.m.r. spectroscopy and the results provided by these calculations. The 12-oxodibenz[c,f]azocine derivative (2I) apparently exists preferentially in a boat conformation as a consequence of a weakly bonding interaction between N(6) and the C(12) carbonyl function.