Photoinduced Electron Transfer Initiated Activation of Organoselenium Substrates as Carbocation Equivalents: Sequential One-Pot Selenylation and Deselenylation Reaction

Article abstract of DOI:10.1021/jo00103a031

The investigation presented in this paper explores the mechanistic aspects and synthetic potentials of PET activation of organoselenium substrates.Fluorescence quenching of ¹DCN^* by a number of organoselenium compounds (RCH2SeR', 1-4), correlation of the fluorescence quenching rate constants with the oxidation potentials of 1-4, and the dependence of photodissociation quantum yields of 1-4 on their concentration suggests the occurence of electron transfer processes between ¹DCN^* and 1-4.Steady-state photolysis of 1-4 in the presence of ¹DCN^* leads to the efficient one-electron oxidative heterolytic dissociation of the carbon-selenium bond to produce the carbocation (RCH2(1+) or equivalent) and radical-centered selenium species (R'Se(.)) via the intermediacy of cation-radical <(RCH2SeR')(1+.)>.Nucleophilic assistance in the fragmentation of (RCH2SeR')(1+.) by methanol has been suggested on the basis of products obtained from the control PET reaction of neopentyl phenyl selenide (8).The synthetic utility of these findings has been demonstrated for the deselenylation (Table 4) as well as one-spot sequential selenylation-deselenylation (Table 5) reactions.