AM1 study of conformational properties of five- to eight-membered ring ketenimines

AM1 semi-empirical SCF MO calculations have been used to investigate the conformational and configurational interconversion pathways for five- to eight-membered ring ketenimines 3-6. Compounds 3 and 4 can exist as a racemic modification of two enantiomeric twist forms. The planar achiral forms of these compounds are higher in energy by 25 and 95 kT mol(-1) respectively. Two minimum-energy conformations are found for 5; the chair (5-C) geometry is about 95 kJ mol(-1) less stable than the envelope (5-E) form. For compound 6, two conformations with similar heats of formation are found; the third minimum-energy geometry is about 15 kT mol(-1) higher in energy. (C) 1998 Elsevier Science B.V. All rights reserved.