Generally, amine‐catalyzed enantioselective transformations rely on chiral enamine or unsaturated iminium intermediates. Herein, we report a protocol involving dual activation by an aromatic iminium and hydrogen‐bonding. An enantioselective aza‐Michael–Henry domino reaction of 2‐aminobenzaldehydes with nitroolefins has been developed through this protocol using primary amine thiourea catalysts to provide
通常,胺催化的对映选择性转化依赖于手性烯胺或不饱和亚胺中间体。在这里,我们报告了一个涉及芳香亚胺和氢键双重激活的协议。2-氨基苯甲醛与硝基烯烃的对映选择性氮杂-迈克尔-亨利多米诺反应已通过该方案使用伯胺硫脲催化剂开发,以中等收率和高达 90% ee提供各种 3-硝基-1,2-二氢喹啉. 通过反应中间体的 ESI 质谱检测证实了催化对映选择性反应的机制。形成的产物是在重要生物和药物分子的骨架中发现的亚结构。
Synthesis of function-oriented 2-phenyl-2H-chromene derivatives using l-pipecolinic acid and substituted guanidine organocatalysts
作者:Bhaskar C. Das、Seetaram Mohapatra、Philip D. Campbell、Sabita Nayak、Sakkarapalayam M. Mahalingam、Todd Evans
DOI:10.1016/j.tetlet.2010.02.143
日期:2010.5
Organocatalytic domino oxa-Michael/aldol reactions between salicylaldehyde with electron deficient olefins are presented. We screened guanidine, 1,1,3,3-tetramethylguanidine (TMG) and L-pipecolinic acid as organocatalysts for this transformation. 3-Substituted 2-phenyl-2H-chromene derivatives are synthesized with high yields and with poor enantioselectivity (5-17% ee) using L-pipecolinic acid while TMG works well with cinnamaldehyde without using co-catalyst. These 3-substituted-2-phenyl-2H-chromene derivatives are further derivatized to synthesize triazole and biotin-containing chromene derivatives, to facilitate purification of protein targets. (C) 2010 Elsevier Ltd. All rights reserved.
Asymmetric Direct Michael Reactions of Cyclohexanone with Aromatic Nitroolefins in Water Catalyzed by Novel Axially Unfixed Biaryl-Based Bifunctional Organocatalysts
new family of axiallyunfixedbiaryl-basedwater-compatible bifuctional organocatalysts were designed and synthesized for the asymmetric direct Michael reaction of cyclohexanone with various nitroolefins in water. One of the organocatalysts incorporates pyrrolidine and arylsulfonamide motifs as active organocatalytic sites, and axiallyunfixed biaryl as a skeleton; with this organocatalyst, the direct
设计并合成了一类新的轴向未固定联芳基水相容双功能有机催化剂,用于环己酮与水中各种硝基烯烃的不对称直接迈克尔反应。其中一种有机催化剂包含吡咯烷和芳基磺酰胺基序作为活性有机催化位点,以及轴向未固定的联芳基作为骨架;使用这种有机催化剂,直接迈克尔反应很容易进行,以高产率(高达 99% 的产率)提供所需的迈克尔加合物,并具有高水平的立体控制(高达 >99:1 dr 和 94% ee)。