Different bio/Lewis acid-catalyzed stereoselective aldol reactions in various mediums
作者:Tülay Yıldız、Hasniye Yaşa、Belma Hasdemir、Ayşe S. Yusufoğlu
DOI:10.1007/s00706-017-1967-z
日期:2017.8
Brønsted acids were used for asymmetric aldol reactions of aromatic, heteroaromatic, cyclic, and acyclic six ketones and eleven aldehydes. Optimum reaction conditions were determined by changing temperature and enzyme, ketone, aldehyde, solvent, cofactors types, amounts, and ratios. PPL (porcine pancreatic lipase) of animal and AL-AN (amano lipase A from Aspergillus niger) of fungal origins were the
(1R,2R)-Bis[(S)-prolinamido]cyclohexane Modified with Ionic Groups: The First C2-Symmetric Immobilized Organocatalyst for Asymmetric Aldol Reactions in Aqueous Media
作者:Sergei V. Kochetkov、Alexandr S. Kucherenko、Sergei G. Zlotin
DOI:10.1002/ejoc.201100707
日期:2011.10
The first C2-symmetric immobilized organocatalyst for asymmetricaldolreactions containing the (1R,2R)-bis[(S)-prolinamido]cyclohexane unit tagged with two imidazolium+/PF6– ion pairs has been synthesized. In its presence, (hetero)aromatic aldehydes reacted with linear or cyclicketones in aqueous media to yield chiral aldols with high diastereo- and enantioselectivities and the catalyst could be
AbstractThe CoCl2/L‐proline (1:2) system was found to be an excellent catalyst for direct aldol reactions. Excellent yields (up to 93 %) and a significant improvement in diastereoselectivity (anti/syn up to 45:1) as well as enantioselectivity (up to more than 99 % ee) compared with using proline as the sole catalyst were observed. This catalyst system was successfully applied to both cyclic and acyclic ketones in combination with aromatic and aliphatic aldehydes. In situ chelation of CoCl2 and proline (1:2) is proposed to promote the reaction through a six‐membered Zimmermann–Traxler type transition state involving the positioning of proline‐enamine and the aldehyde through chelation to CoII.