The cooperative effect of a hydroxyl and carboxyl group on the catalytic ability of novel β-homoproline derivatives on direct asymmetric aldol reactions
作者:Yoshikazu Hiraga、Triana Widianti、Tsuyoki Kunishi、Manabu Abe
DOI:10.1016/j.tetasy.2011.01.025
日期:2011.1
prepared compounds were used as organocatalysts in the direct asymmetric aldol reaction of 4-nitrobenzaldehyde with several ketones. Among these catalysts, (R)-2-hydroxy-2-((S)-pyrrolidin-2-yl)acetic acid (R,S)-1a showed good catalytic ability in the formation of aldol product 13 (up to 69% ee, 95% yield), which was similar to the results catalyzed by l-proline (71% ee, 96% yield). Relatively low yields
合成了新的β-高脯氨酸衍生物2-羟基-2-(吡咯烷-2-基)乙酸(R,S)-和(S,S)-1a - d。在4-硝基苯甲醛与几种酮的直接不对称醛醇缩合反应中,所有制备的化合物均用作有机催化剂。在这些催化剂中,(R)-2-羟基-2-((S)-吡咯烷基-2-基)乙酸(R,S)-1a在形成醛醇产物13中显示出良好的催化能力。(最高ee为69%,产率为95%),与l-脯氨酸催化的结果相似(ee为71%,产率为96%)。相对低的收率和对映选择性低在由(催化羟醛缩合反应中观察到小号,小号) - 1A,例如,13 55%产率和13%的ee值获得。由甲基保护的羧酸1b和酯1c,d催化的醛醇缩合反应在13的形成过程中产生的化学收率和对映选择性低得多。(R的协同作用)-构型的羟基和羧基被发现在醛醇缩合反应中诱导对映选择性中起重要作用。相对高的非对映选择性(反:顺 = 85:15)和对映选择性(反,83%ee)的