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Communication | Regular issue | Vol 12, No. 1, 1979, pp.21-27
Published online, 1st January, 1970
DOI: 10.3987/R-1979-01-0021
Photochemical Cyanation of Quinolines and Isoquinolines. Participation of Enhanced Basicity in Excited Singlet States

Naganori Numao and Osamu Yonemitsu*

*Faculty of Pharmaceutical Sciences, Hokkaido University, Kita 12 Nishi 6, Kita-ku, Sapporo, Hokkaido 060-0812, Japan

Abstract

When 7-methoxyquinoline and excess NaCN in aqueous MeCN was irradiated with a 100 W high pressure mercury lamp under bubbling O2 for 3.5 hr to give 8-cyano-7-methoxyquinoline in 39% yield, whereas quinoline was recovered unchanged under similar conditions. 6-Methoxyquinoline was more reactive and gave 5-cyano-6- methoxyquinoline in 48% yield after irradiation for 1.5 hr. Isoquinoline gave 3-cyanoisoquinoline only in 11% yield, while 6- and 7-methoxyisoquinolines gave 5-cyano-6-methoxyisoquinoline (12%) and 8-cyano-7-methoxyisoquinoline (38%), respectively. The mechanism involving the participation of excited singlet state pKa was elucidated on the basis of quantum yield measurements for disappearance of 6- and 7-methoxyquinolines and for formation of the products and their pH dependence.