Photochemical reactions of o-alkenylphenols and 1-alkenyl-2-naphthol with alkylamines: amination via photoinduced proton transfer

Abstract

Irradiation of o-alkenylphenols 1a–c and 2a–e in the presence of alkylamines gave o-(1-alkylaminoalkyl) phenols 4a–n and 5a–e in relatively good yields. Deprotonation of these o-alkenylphenols by the amines occurs in the excited singlet state to give the excited singlet state of the phenolate anion 7 and the ammonium ion. The proton transfer from the ammonium ion to the alkenyl group of 7 generates the zwitterion 8 that allows the nucleophilic addition of the amine at the benzylic cation centre. Similar photoamination of 1-(2-methylpropenyl)-2-naphthol 3 with alkylamines occurred to give 1-(1-alkylamino-2-methylpropyl)-2-naphthols 6a–b.