Cooperative electron transfer fragmentation reactions. Amplification of a photoreaction through a tandem chain fragmentation of acceptor and donor pinacols

Photofragmentation reactions occurring as a consequence of activation by oxidation or reduction of excited states have been observed for a variety of organic molecules, especially for donors such as amines, pinacols, and substituted diarylethanes.1-9 In many cases the fragmentation of the ion radical produces a stable (even-electron) product and a redox active radical.3,4 As a typical example, the cation radicals of electron-rich pinacols such as 1 (KHKH) generate a ketone, K, and the relatively strong reducing ketyl radical, KH• (eq 1).10-12 In previous studies, we have