Bimolecular hydrogen transfer in phenalene by a stepwise ene-like reaction mechanismElectronic supplementary information (ESI) available: The unimolecular hydrogen transfer process; the transition structures corresponding to the dimerization process in Fig. 1. See DOI: 10.1039/c0cc00183j

For the hydrogen transfer of phenalene, a bimolecular ene-like mechanism is proposed, which is preferable over the hypothesized unimolecular rearrangement in the literature. Unique SOMO–SOMO π-bonding of phenalenyl reduces the barriers of pericyclic reactions significantly. π-bonding between radicals is being recognized as a novel type of bonding interaction. This paper adds to the use of this interaction by pointing out its effect on reaction barriers. [ABSTRACT FROM AUTHOR]