A chiral organocatalytic polymer-based monolithic reactor
作者:Valerio Chiroli、Maurizio Benaglia、Alessandra Puglisi、Riccardo Porta、Ravindra P. Jumde、Alessandro Mandoli
DOI:10.1039/c4gc00031e
日期:——
properly modified enantiomericallypure imidazolidinone inside a stainless steel column in the presence of dodecanol and toluene as porogens afforded the first example of a chiral organocatalyst immobilized onto a monolithic reactor. Organocatalyzed cycloadditionsbetween cyclopentadiene and cinnamic aldehyde were performed under continuous-flow conditions; by optimizing the experimental set up, excellent
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。
<i>e</i><i>xo</i>-Selective Asymmetric Diels−Alder Reaction Catalyzed by Diamine Salts as Organocatalysts
作者:Taichi Kano、Youhei Tanaka、Keiji Maruoka
DOI:10.1021/ol060621i
日期:2006.6.1
[reaction: see text] A novel binaphthyl-based diamine (R)-2 was designed and synthesized. A protonic acid-(R)-2 salt catalyst has the advantage of exhibiting unprecedented high exo selectivity in the asymmetricDiels-Alderreaction of alpha,beta-unsaturated aldehydes. For instance, the reaction between cinnamaldehyde and cyclopentadiene in the presence of 12 mol % of binaphthyl-based diamine (R)-2
Bronsted acid-assisted chiral Lewis acid (BLA) was highly effective as a chiral catalyst for the enantioselective Diels−Alder reaction of both α-substituted and α-unsubstituted α,β-enals with various dienes. Hydroxy groups in opticallyactive binaphthol derivatives and boron reagents with electron-withdrawing substituents were used as Bronsted acids and Lewis acids, respectively. Intramolecular Bronsted
布朗斯台德酸辅助的手性路易斯酸 (BLA) 作为手性催化剂非常有效,可用于 α-取代和 α-未取代的 α,β-烯醛与各种二烯的对映选择性 Diels-Alder 反应。光学活性联萘酚衍生物中的羟基和具有吸电子取代基的硼试剂分别用作布朗斯台德酸和路易斯酸。手性 BLA 催化剂中的分子内布朗斯台德酸在加速 Diels-Alder 反应速率和产生高水平的对映选择性方面发挥了重要作用。特别是,由于手性 BLA 催化剂中羟基芳基在过渡态组装中的分子内氢键相互作用和有吸引力的 π-π 供体-受体相互作用,实现了优异的对映选择性。
Diels-Alder Reaction in Air- and Moisture-Stable Zinc-Containing Ionic Liquids
Diels-Alderreactions in a number of air- and moisture-stable dialkylimidazolium halide-ZnCl 2 ionicliquids are reported. High yields and high endo selectivities have been observed. The ionicliquids could then be recyclable without loss of reactivity.