Conformational and configurational properties of nine-membered cyclic diketenimines

An investigation employing the AM1 semiempirical SCF MO method to calculate the structure optimization, conformational and configurational interconver sion pathways for two diastereoisomeric forms of 3,5-, 1,7- and 1,5-diazacy clonona-1,2,5,6-tetraene (1-3) has been undertaken. The (+/-)-diastereoisom ers of 1-3 are calculated to be 17.8, 13.7 and 10.6 kJ mol(-1) more stable than the meso- (or meso-like) isomers, respectively. Configurational interc onversion between the two diastereoisomers of 1-3 can take place by nitroge n atom inversion and require 96.2, 74.7 and 104.6 kJ mol(-1), respectively. (C) 1999 Elsevier Science B.V. All rights reserved.