Ring-opening reaction of cyclobutene radical cation: Effect of solvent on competing pathways

We have recomputed the activation barriers for the different modes of ring opening of the cyclobutene radical cation (see: Sastry, G. N.; Bally, T.; H rouda, V.; Carsky, P. J. Am. Chem. Sec. 1998, 120, 9323) in CHCl3, a typica l solvent for studies of radical cation reactions, by a polarizable continu um model. Thereby, we found a clear preference for the reaction leading dir ectly to trans-butadiene radical cation via a cyclopropenyl-carbinyl type r adical cation, in contrast to expectations of a normal "electrocyclic" path way leading to cisbutadiene radical cation.