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Paper | Regular issue | Vol 57, No. 2, 2002, pp.269-292
Published online, 1st January, 1970
DOI: 10.3987/COM-01-9392
An Efficient Transformation of Substituted N-Acyl-α-dehydro(1-naphthyl)alanines into 1,2-Dihydrobenzo[f]quinolinone Derivatives via Photoinduced Intramolecular Electron Transfer

Toyohisa Motohashi, Kei Maekawa, Kanji Kubo, Tetsutaro Igarashi, and Tadamitsu Sakurai*

*Laboratory of Organic Chemistry, Faculty of Technology, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan

Abstract

The irradiation of substituted (Z)-N-acyl-α-dehydro(1-naphthyl)alanines (1) having the dialkylamino donor on the carboxamide side chain in methanol was found to give 1,2-dihydrobenzo[f]quinolinone derivatives (2) in good yields, which were formed via the electron-transfer reaction in the excited-state (E)-isomers, while intramolecular photocyclization reactions in the (Z)- and (E)-isomers afforded minor amounts of benzo[f]isoquinolines (3) and 1-azetines (4), respectively. The replacement of the N-acetyl group by the benzoyl (having stronger electron-withdrawing ability and larger steric bulkiness than the former) increased the selectivity for 2 and 4, and this increased selectivity was mainly reflected in a great lowering of that for 3.