作者:Masayuki Yokota、Rei Koyama、Hiromi Hayashi、Satoko Uchibori、Tsuyoshi Tomiyama、Hiroshi Miyazaki
DOI:10.1055/s-1994-25706
日期:——
The simple and regioseletive oxidation of 6-alkylazulene derivatives with an electron-withdrawing substituent at the 1-position of the azulene ring is described. Oxidation with molecular oxygen proceeds smoothly in the presence of a base such as potassium acetate (KOAc) or tetrabutylammonium hydroxide (Bu4NOH), and appears to proceed via enolization of the azulene derivatives. Oxidation of 6-isopropylazulene derivatives gave tertiary alcohols, which were easily converted to primary alcohols. Oxidation of 6-methylazulene derivatives provided azulene-6-carboxylate derivatives but dimethhyl azulene-1,6-dicarboxylate, which had been obtained by the oxidation of methyl 6-methylazulene-1-carboxylate, was found to be reduced selectively at the 6-position by sodium borohydride (NaBH4). In contrast, demethoxycarbonylation of dimethyl azulene-1,6-di-carboxylate with anhydrous phosphoric acid (100%PA) proceeded selectively at the 1-position to give methyl azulene-6-carboxylate. Those compounds obtained by the oxidation of 6-alkylazulenes are useful key intermediates for further modifications of the side chains at the 6-position of azulenes.
描述了在薁环 1 位具有吸电子取代基的 6-烷基薁衍生物的简单和区域选择性氧化。分子氧的氧化在乙酸钾 (KOAc) 或氢氧化四丁基铵 (Bu4NOH) 等碱存在下顺利进行,并且似乎是通过甘菊环衍生物的烯醇化进行的。 6-异丙基薁衍生物的氧化得到叔醇,该叔醇很容易转化为伯醇。 6-甲基薁衍生物的氧化提供了薁-6-羧酸酯衍生物,但通过氧化6-甲基薁-1-甲酸甲酯而获得的二甲基薁-1,6-二羧酸酯被发现在6-位被选择性还原。硼氢化钠(NaBH4)的位置。相比之下,1,6-二甲酸二甲酯与无水磷酸(100%PA)在1位选择性地进行脱甲氧基羰基化,得到6-甲酸甲酯。通过氧化 6-烷基甘菊环得到的那些化合物是进一步修饰甘菊环 6 位侧链的有用的关键中间体。