Effect of additives on the proline-catalyzed ketone–aldehyde aldol reactions
作者:Petri M. Pihko、Katri M. Laurikainen、Annina Usano、Annika I. Nyberg、Jatta A. Kaavi
DOI:10.1016/j.tet.2005.09.070
日期:2006.1
The effect of bases, acids, and water as additives in proline-catalyzed ketone–aldehyde aldol reactions has been studied. While the reaction appears to be relatively tolerant to small amounts of tertiary amine bases or weak acids, it stops completely with strong acids. The use of water as an additive had a highly beneficial effect on reactions that were conducted with a stoichiometric ratio of ketone
to >99 % enantiomeric excess (ee) have been obtained by proline catalysis in excellent yields under experimentally simple solvent-free conditions. Efficient mixing of all the components is accomplished by applying a mechanochemical technique (ballmilling). The catalysis is air and moisture tolerant and can be performed with non-purified starting materials. Even mixtures of solely solid compounds react
Chiral picolylamines for Michael and aldol reactions: probing substrate boundaries
作者:Thomas C. Nugent、Ahtaram Bibi、Abdul Sadiq、Mohammad Shoaib、M. Naveed Umar、Foad N. Tehrani
DOI:10.1039/c2ob26382c
日期:——
organocatalyst template, a vicinal chiral diamine based on a pyridine-primary amine motif. The addition of cyclohexanone to β-nitrostyrene has many catalyst solutions, but cyclopentanone and isobutyraldehydeadditions continue to be challenging. PicAm-3 (10 mol%) readily allows the Michael addition of cyclopentanone or isobutyraldehyde (5.0 equiv.) to β-nitrostyrene derivatives. By contrast, PicAm-1 (7.0 mol%)
Highly Stereoselective and Scalable <i>anti</i>-Aldol Reactions Using <i>N</i>-(<i>p</i>-Dodecylphenylsulfonyl)-2-pyrrolidinecarboxamide: Scope and Origins of Stereoselectivities
作者:Hua Yang、Subham Mahapatra、Paul Ha-Yeon Cheong、Rich G. Carter
DOI:10.1021/jo1015008
日期:2010.11.5
A highly enantio- and diastereoselective anti-aldol process (up to >99% ee, >99:1 dr) catalyzed by a proline mimetic—N-(p-dodecylphenylsulfonyl)-2-pyrrolidinecarboxamide—has been developed. Catalystloading as low as 2 mol % can be employed. Use of industry-friendly solvents for this transformation as well as neat reaction conditions have been demonstrated. The scope of this transformation on a range
一种由脯氨酸模拟物N- (对十二烷基苯磺酰基)-2-吡咯烷甲酰胺催化的高度对映和非对映选择性反羟醛过程(高达 >99% ee,>99:1 dr)已被开发出来。可以使用低至2mol%的催化剂负载。已经证明可以使用工业友好型溶剂进行这种转化以及纯净的反应条件。探索了这种对一系列醛和酮的转化范围。密度泛函理论计算表明,增强的非对映选择性的起源是由于磺酰胺、亲电子试剂和催化剂烯胺之间存在非经典氢键,有利于 Houk−List 模型中主要的反 Re 醛醇TS 。
The application of a structurally simple, recyclable, and large-scale l-prolinamide catalyst for asymmetric aldol reactions
作者:Zhi Guan、Yuan Luo、Bao-Qiang Zhang、Krystal Heinen、Da-Cheng Yang、Yan-Hong He
DOI:10.1016/j.tetasy.2014.04.009
日期:2014.5
With heterocyclic ketones or cyclohexanone, the aldolreactions gave products in high yields and with respectable enantioselectivities (87–99% ee) and diastereoselectivities (up to >99:1 anti/syn). The catalyst could be recycled and reused up to seven times resulting in good yields and with good selectivities. This catalyst is also efficient in large-scale reactions with the enantioselectivities remaining