MCSCF study of the thermal isomerization of tricyclo[2.1.0.02,5]pentane to 1,3-cyclopentadiene

The isomerization of tricyclo[2.1.0.02,5]pentane to 1,3-cyclopentadiene was studied using ab initio calculations at the multiconfiguration self-consistent field level of theory. Single-point energy calculations were also performed using the MCQDPT2 and CCSD(T) methods. The isomerization process was found to proceed through a concerted, asynchronous pathway characterized as a disrotatory ring opening of the bicyclobutane moiety. The activation barrier was found to be 42 kcal/mol. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004