AM1 study of conformational properties of cyclohexaketene and expanded cyclohexaketenes

Semi-empirical AMI SCF-MO calculations are used to calculate the structure optimization and conformational interconversion pathways in cyclohexaketene (1) and expanded cyclohexaketenes 2-4. Compounds 1-4 have two symmetrical energy-minimum conformations, namely chair and twist-boat. The chair confor mation is the most stable geometry for compounds 1-4. Cyclohexaketenes 1-4 are 80-120 kJ mol(-1) more stable than the corresponding tris-cyclobutenedi one derivatives. (C) 1999 Elsevier Science B.V. All rights reserved.