27613-46-3Relevant articles and documents
Kinetics of the thermolysis of [n.2.2]propellanes and related compounds. Mechanism of the thermolysis of bicyclo[2.2.0] hexanes
Wiberg, Kenneth B.,Caringi, Joseph J.,Matturro, Michael G.
, p. 5854 - 5861 (2007/10/02)
The thermolyses of a series of 1,4-bridged bicyclo[2.2.0]hexanes have been studied. With bridges having three or more carbons, the compounds have higher activation energies than for bicyclo[2.2.0]hexane, indicating that the bridge prevents the formation of a chair cyclohexane-1,4-diyl, forcing the reaction to proceed via an orbital symmetry disallowed process. It appears likely that [2.2.2]propellane and its derivatives react via the same mechanism, and the driving force from strain relief appears to be the major factor in reducing its activation energy. The thermolysis of the relatively unstrained [3.3.2]propellane occurs at a significantly higher temperature and leads to a mixture of products which also were found in the thermolysis of 1,5-dimethylenecyclooctane. The thermolysis of the latter at 420°C formed the propellane. The strain relief in the cleavage of the central bond in this group of propellanes were estimated via a combination of ab initio and molecular mechanics calculations and was found to be correlated with the changes in activation energy. The thermolyses of [3.2.1]- and [4.2.1]propellanes also are reported and were found to be less reactive than expected on the basis of strain energy relief.
