A comparison of electron transfer reagents in the reductive opening of epoxides: reasons for the superiority of titanocene based complexes

Several commonly used electron transfer reagents were compared in their reactivity towards three epoxides. These substrates were designed to allow for a distinction between competing courses of the reaction. It was found that titanocene reagents were clearly superior due to their low Lewis acidity, high reduction tendency towards epoxides, and low reduction tendency towards the pivotal β-metal oxy radical intermediates.