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Note | Regular issue | Vol 60, No. 3, 2003, pp.637-654
Published online, 20th January, 2003
DOI: 10.3987/COM-02-9676
meta-Substituent Effects on the Photocyclization of Aryl-substituted N-Acyl-α-dehydroalanine Derivatives

Kei Maekawa, Hiroo Kajiwara, Yoshiyuki Iseya, Tetsutaro Igarashi, and Tadamitsu Sakurai*

*Departmnet of Applied Chemistry, Faculty of Engineering, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan

Abstract

On irradiation in methanol, the title compounds having chloro, trifluoromethyl or methyl group at the meta position on the styryl benzene ring gave 6-substituted (2) and 8-substituted (3) 1-methyl-3-(methylaminocarbonyl)isoquinolines along with 1-azetines. The preferential formation of 2 to 3 was explained in terms of steric effects on the cyclization process from the excited-state (Z)-isomer. The methoxy group introduced at the same meta position exerted dramatical electronic and steric effects on the excited-state cyclization pathway giving rise to regioselectively 6-substituted 2-quinolinone and isoquinoline derivatives. The 1-naphthyl substituent in the title compounds was found to have the same effects on the cyclization pathway as the methoxyphenyl group.