During attempts to ring-open a highly hindered epoxide, traditional methods were found to be ineffective. An alternative strategy for opening epoxides was implemented that employed a potassium carboxylate in the presence of its conjugate acid in a solvent mixture containing polar and potassium-sequestering components. A systematic analysis of the components of the reaction mixture indicated that the addition of the conjugate acid was the most important feature for providing good conversion. This reaction appears to be general for most classes of carboxylic acids including cinnamic, aromatic, and highly hindered carboxylic acids (30%–79% yield) and only fails with weak carboxylate nucleophiles. Three highly substituted and hindered cyclohexene oxide derivatives were examined for reactivity and the reaction conditions appear to tolerate a variety of functional groups to provide the ring-opened species. This pH-moderate system proved useful for hindered cyclic epoxides when all other techniques failed and should prove general to a wide spectrum of epoxide and carboxylic acid partners in those cases where the use of a strong Lewis or protic acid catalyst, or a strong basic nucleophile, is inappropriate.
在尝试开环一个高度阻碍的环氧化物时,发现传统方法无效。实施了一种替代策略来打开环氧化物,该策略利用了存在其共轭酸的钾羧酸盐,在含有极性和钾离子螯合成分的溶剂混合物中。对反应混合物组分的系统分析表明,添加共轭酸是提供良好转化的最重要特征。这种反应似乎适用于大多数类别的羧酸,包括肉桂酸、芳香族和高度阻碍的羧酸(30%–79% 收率),只有对弱羧酸亲核试剂失败。对三种高度取代和阻碍的环己烯氧化物衍生物进行了反应性检验,反应条件似乎能容忍各种官能团以提供开环物种。这种pH适中的体系在所有其他技术失败时对阻碍的环氧化物非常有用,并且在不适合使用强Lewis酸或质子酸催化剂,或强碱亲核试剂的情况下,应该适用于广泛的环氧化物和羧酸配体。