The [1,3]-hydrogen shift in cyclopropene. Does it exist?

Abstract

The [1,3]-hydrogen shift in cyclopropene has been investigated by ab initio calculations. At Hartree-Fock and Møller-Plesset levels of theory the Woodward-Hoffmann forbidden suprafacial hydrogen migration is calculated to be a concerted reaction, although the energy of the transition structure at levels including electron correlation is very close to the dissociation limit, cyclopropenyl radical and a hydrogen atom. Sufficiently high-level MCSCF calculations concur with these results, predicting that a concerted [1,3]-hydrogen shift should be a few kcal/mol lower in energy than the dissociation process.