Electron-Transfer Reactions. Oxidation of Grignard Reagents in the Presence of an Aminoxyl as a Radical-Trapping Agent

Article abstract of DOI:10.1021/jo00015a029

The indole bisnitrone 1 (E_1/2red = -0.125 V vs NHE in DMF) reacts with a series of Grignard reagents (RMgX) including primary, secondary, and tertiary alkyls and benzyl and phenyl derivatives, which show different E_ox, by single electron transfer to form C-centered radicals corresponding to the Grignard used.The radicals produced in the reaction were trapped by the (arylimino)indolinone nitroxide 5 to form the alkylated hydroxylamines 6.When the reaction is carried out with a "cyclizing Grignard" such as 5-hexenylmagnesium bromide, the uncyclized (5-hexen-1-yl) 6g and cyclized (methylcyclopentyl) 6h alkylated hydroxylamines are both isolated.In all cases, the Marcus theory treatment predicts high electron-transfer rate constants.