Theoretical study of conformation and dynamic behaviour of [3.3]orthocyclophane and heterocyclic analogues

Both the conformational equilibria and the dynamic behaviour of NX-di-subst ituted 3,12-di-aza-[3.3]orthocyclophane (R = H, COCH3, COPh, tosyl) were ca lculated by the semi-empirical PM3 method and at the ab-initio level of the ory (HF 6-31G*) in the light of inconsistent previous experimental results. The preferred conformer proved to be generally the chair form (anti-peripl anar) and the exchange phenomena, which could be studied by dynamic NMR spe ctroscopy, result from the ring interconversional process and the restricte d rotation about the exo-cyclic partial C,N double bond. (C) 2001 Elsevier Science Ltd. All rights reserved.