1997 年 55 巻 3 号 p. 196-206
A biomimetic oxidizing system “Cu2+-ascorbic acid-O2” was effective for selective conversion of ο-alkoxyphenols into oxido-labile catechols. First direct preparation of 3-hydroxycoumarins from coumarins was achieved by using this system. The oxidizing system hydroxylated phenols to afford catechols and hydroquinones. An unusual substituent effect was observed on this hydroxylation of phenols. Some of the derived catechols and 3-hydroxycoumarins exhibited much greater bio-activities than those of the mother compounds. Mechanistic investigation has revealed that catechols were formed via ipso-substitution of alkoxy groups of ο-alkoxyphenols for hydroxy group.