Synthesis of Chiral 3-Substituted Phthalides by a Sequential Organocatalytic Enantioselective Aldol-Lactonization Reaction. Three-Step Synthesis of (<i>S</i>)-(−)-3-Butylphthalide
作者:Haoyi Zhang、Shilei Zhang、Lu Liu、Guangshun Luo、Wenhu Duan、Wei Wang
DOI:10.1021/jo902118x
日期:2010.1.15
enantioenriched “privileged” scaffold. As a result of the sensitive nature of substrate structures of an organocatalytic enantioselective aldol reaction, after extensive optimization of reaction conditions, catalyst l-prolinamide alcohol IV is identified as the best promoter. Interestingly, it is found that in this reaction, addition of an acid additive PhCO2H can significantly enhance reaction efficiency with
易于构建重要分子框架的有效方法的开发是有机合成的重要目标。手性3-取代的邻苯二甲酸酯广泛分布在大量具有广泛,有效和潜在发展前景的生物活性的天然产物中。在这项研究中,我们发现了2-甲酰基苯甲酸酯与酮/醛的前所未有的有机催化不对称醛醇内酯化反应,可方便地构建对映体富集的“特权”支架。由于有机催化对映选择性醛醇缩合反应的底物结构的敏感性质,在广泛优化反应条件后,催化剂1-脯氨酰胺醇IV被确定为最佳启动子。有趣的是,发现在该反应中,添加酸添加剂PhCO 2 H可以显着提高反应效率,而该方法仅使用低至2.5mol%的IV。此外,由于反应条件对顺序的羟醛-内酯化过程敏感,而又不影响对映选择性和外消旋作用,因此在存在K 2 CO 3的情况下,必须除去催化剂以用于随后的容易的内酯化反应。醛醇内酯化方法是制备具有高对映选择性的合成上和生物学上重要的3-取代的邻苯二甲酸酯的有力方法。报道了3-丁基邻苯二甲酸酯的天然产物的三步催化不对称合成。
Catalytic Asymmetric Conjugate Addition of Carboxylic Acids via Oxa-Michael Reaction of Peroxy Hemiacetals followed by Kornblum DeLaMare Fragmentation
作者:Biswajit Parhi、Sanjay Maity、Prasanta Ghorai
DOI:10.1021/acs.orglett.6b02463
日期:2016.10.21
Disclosed herein an overall methodology constitutes an equivalent to the long sought after enantioselective intramolecular oxa-Michael (IOM) reaction of carboxylic acids. An organocatalyzed IOM reaction of in situ formed peroxy hemiacetals followed by a Kornblum DeLaMare type rearrangement cascade provides a broad class of chiral lactones in good yields and with excellent enatioselectvities. Remarkably