Reactivity of a trivalent phosphorus radical cation as an electrophile toward pyridine derivatives

The reaction of methylviologen (MV²⁺) with tributylphosphine (1p) and diethylphenylphosphine (1q) in the presence of an alkyl-substituted pyridine (2) was found to take place through a single-electron transfer (SET) from 1 to MV²⁺ followed by nucleophilic attack by 2 on the resulting phosphine radical cation 1^•+. Kinetic examination showed that, in the transition state for the reaction of 1^•+ with 2, an unpaired electron is largely delocalized to the pyridine moiety. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:152–157, 2000