Facile Formations of<i>o</i>- and<i>p</i>-Tropoquinone Mono- and Bisacetals by Anodic Oxidations of 2,3-, 2,5-, 2,7-, and 4,5-Dimethoxytropones
作者:Akira Mori、Tadahiko Kubota、Hitoshi Takeshita
DOI:10.1246/bcsj.61.3965
日期:1988.11
o- and p-Tropoquinone mono- and bisacetals (tetramethoxycycloheptadienones) were prepared from 2,3-, 2,5-, 2,7-, and 4,5-dimethoxytropones by means of anodic oxidations in practical yields. Cerium(IV) salt oxidations of dimethoxytropones afforded a mixture of products i.e., a hydrolysis product and/or a methanol adduct of tropoquinone bisacetals. By treating with sulfuric acid in a mixture of acetic acid and acetic anhydride, 4,4,7,7- and 2,2,7,7-tetramethoxycycloheptadienones gave the Thiele-type reaction products with a high positional selectivity. Similarly, 2-bromo-7-methoxytropone was anodically oxidized to 4,4,7,7-tetramethoxycycloheptadienone and its 2-bromo derivative. The mechanism of the reaction is also discussed in detail.
o-和p-萜喹酮的单醚和双醚(四甲氧基环七烯酮)是通过阳极氧化从2,3-、2,5-、2,7-和4,5-二甲氧基萜烯制备的,得到了较高的实用产率。使用铈(IV)盐对二甲氧基萜烯进行氧化,可以得到一系列产物的混合物,即水解产物和/或萜喹酮双醚的甲醇加成物。通过在醋酸和醋酸酐的混合物中与硫酸反应,4,4,7,7和2,2,7,7-四甲氧基环七烯酮生成了具有高位置选择性的Thiele型反应产物。同样,2-溴-7-甲氧基萜烯经过阳极氧化也得到了4,4,7,7-四甲氧基环七烯酮及其2-溴衍生物。反应机制也进行了详细讨论。