Reaction of Diketene with Grignard Reagents in the Presence of Cobalt Catalyst. A Convenient Method for the Synthesis of 3-Methylenealkanoic Acids Leading to Terpenoids
Primary alkyl Grignardreagents react regioselectively with diketene in the presence of cobalt(II) iodide to afford 3-methylenealkanoic acids in good yields. The synthetic utility of this reaction is demonstrated in the syntheses of terpenoids by two methods. Utilizing the isomerization of double bond of 3-methylenealkanoic acids, geranic acid and farnesic acid were obtained in two steps. Another method
在碘化钴 (II) 存在下,伯烷基格氏试剂与双烯酮发生区域选择性反应,以良好的收率得到 3-亚甲基链烷酸。该反应的合成效用在通过两种方法合成萜类化合物中得到证明。利用3-亚甲基链烷酸双键异构化,分两步得到香叶酸和法呢酸。另一种方法,即相应烯丙基酯的串联 [3,3] sigmatropic 重排用于合成 C18-天竺葵保幼激素。