Abstract
The investigation presented in this paper explores the mechanistic aspects and synthetic potentials of photosensitized electron transfer (PET) promoted reductive activation of organoselenium substrates. PET activation of substrates 1 − 5 is achieved through a photosystem comprised of light-absorbing 1,5-dimethoxynaphthalene (DMN) as electron donor and ascorbic acid as co-oxidant. The fluorescence quenching of 1DMN* by organoselenium compounds 1 − 5, correlation of fluorescence quenching rate constant with the reduction potentials of 1 − 5, and the dependence of photodissociation quantum yields of 1 − 5 on their concentration suggests the occurrence of electron-transfer (ET) processes between 1DMN* and 1 − 5. Steady state photolysis of organoselenium substrates (R2CHSePh) in the presence of 1DMN* and ascorbic acid leads to the cleavage of the −C−Se− bond to produce a carbon-centered radical and PhSe- species via the intermediacy of R2CH−SePh⎤-. The mechanistic interpretation for the reductive activation of −C−Se− bonds and the synthetic utility of observed cleavage pattern is extended for the unimolecular group transfer radical sequences.