evaluation of surface areas, pore dimensions, and catalyst loading. They were used in organocatalyzed Diels–Alder cycloadditions between cyclopentadiene and different aldehydes, affording results comparable to those obtained with the nonsupported catalyst (up to 91% yield and 92% ee in the model reaction between cyclopentadiene and cinnamic aldehyde). The catalysts were recovered from the reaction mixture
据报道,利用两个不同的锚定位点和两个不同的接头,在中孔二氧化硅纳米粒子上合成手性咪唑烷酮。催化剂1 - 4制备来自开始升-苯丙氨酸或升-酪氨酸甲基酯和通过接枝协议或叠氮化物-炔烃铜(I) -催化的环加成支撑所述咪唑啉酮在硅胶上。四种催化剂均通过固态NMR N 2进行了充分表征物理吸附,SEM和TGA,以提供结构评估,包括表面积,孔尺寸和催化剂载量的评估。它们用于环戊二烯与不同醛之间的有机催化Diels-Alder环加成反应,其结果可与无载体催化剂获得的结果相媲美(在环戊二烯与肉桂醛之间的模型反应中,收率高达91%,ee为92%)。通过简单的过滤或离心从反应混合物中回收催化剂。活性最高的催化剂循环使用两次,但催化效率有所降低,而ee的侵蚀也很小。
Immobilization of MacMillan Imidazolidinone as Mac-SILC and its Catalytic Performance on Sustainable Enantioselective Diels-Alder Cycloaddition
(Mac‐SILC) in the pores of silica gel with the aid of an ionic liquid – 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide. The heterogenized organocatalyst was utilized for the enantioselectiveDiels–Alder reaction of cyclopentadiene and cinnamaldehyde, recovered by simple filtration and subsequent evacuation, and repeatedly used up to six times in 81% average chemical yield, 87% ee for endo‐
Improving catalyst activity in secondary amine catalysed transformations
作者:John B. Brazier、Timothy J. K. Gibbs、Julian H. Rowley、Leopold Samulis、Sze Chak Yau、Alan R. Kennedy、James A. Platts、Nicholas C. O. Tomkinson
DOI:10.1039/c4ob01916d
日期:——
Improved catalytic efficiency has been observed in the Diels–Alder cycloaddition by modification of the imidazolidinone architecture.
通过修改咪唑烷酮结构,观察到了Diels-Alder环加成反应的催化效率提高。
Structural effects in pyrazolidinone-mediated organocatalytic Diels–Alder reactions
作者:Eoin Gould、Tomas Lebl、Alexandra M.Z. Slawin、Mark Reid、Andrew D. Smith
DOI:10.1016/j.tet.2010.09.021
日期:2010.11
promoted Diels–Alderreactions evaluated. Systematic variation of the C(5)- and N(2)-substituents indicates that the incorporation of an electron withdrawing substitutent at N(2) and either a Ph or CF3 substitution at C(5) results in optimal catalytic activity. The diastereoisomeric resolution of a model C(5)-Ph substituted pyrazolidinone and its ability to impart modest levels of asymmetric induction
Aqueous Enantioselective Organocatalytic Diels−Alder Reactions Employing Hydrazide Catalysts. A New Scaffold for Organic Acceleration
作者:Mathieu Lemay、William W. Ogilvie
DOI:10.1021/ol051476w
日期:2005.9.1
[reaction: see text] Cyclic hydrazides function as asymmetric organocatalysts in aqueous Diels-Alderreactions. The hydrazide is employed as the catalytic machinery in a compact camphor-derived framework that imparts facial selectivity to the cycloadditions. Kinetic evidence suggests the reaction involves rapid iminium formation.