Intramolecular Photoaddition of Secondary α-(Aminoalkyl)styrenes

Article abstract of DOI:10.1021/jo00075a037

The photophysical and photochemical behavior of a series of α-<(N-methylamino)alkyl>styrenes with two to four methylenes separating the styryl and amino groups and an (aminoalkyl)indene have been investigated and the results compared to those for the intermolecular reaction of α-methylstyrene with diethylamine.Both inter- and intramolecular quenching of styrene fluorescence by the amine is observed, indicative of electron-transfer quenching as the initial step in these reactions.The resulting exciplex undergoes regioselective N-H proton transfer to styrene C-βyielding a biradical, in the case of the intramolecular reaction, and a radical pair, in the case of the intermolecular reaction.Biradical or radical pair combination yields styrene-amine addition products.The conformation of the intermediate exciplex is proposed to control the regioselectivity of the intramolecular N-H proton transfer process.