INTRAMOLECULAR PHOTOADDITION OF SECONDARY ALPHA-(AMINOALKYL)STYRENES

The photophysical and photochemical behavior of a aeries of alpha-[(N- methylamino)alkyl]styrenes with two to four methylenes separating the styryl and amino groups and an (aminoalkyl)indene have been investigat ed and the results compared to those for the intermolecular reaction o f alpha-methylstyrene with diethylamine. Both inter- and intramolecula r quenching of styrene fluorescence by the amine is observed, indicati ve of electron-transfer quenching as the initial step in these reactio ns. The resulting exciplex undergoes regioselective N-H proton transfe r to styrene C-beta yielding a biradical, in the case of the intramole cular reaction, and a radical pair, in the case of the intermolecular reaction. Biradical or radical pair combination yields styrene-amine a ddition products. The conformation of the intermediate exciplex is pro posed to control the regioselectivity of the intramolecular N-H proton transfer process.