On the roles of protic solvents in imidazolidinone-catalyzed transformations.
On the roles of protic solvents in imidazolidinone-catalyzed transformations.
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关于质子溶剂在咪唑啉酮催化转化中的作用。
DOI：
10.1002/anie.201005892
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
Brazier JB
中科院分区：
文献类型：
--
作者：
Brazier JB
在过去的十年里，有机催化激发了合成化学家的想象力，推动了化学合成的边界特别值得注意的是仲胺在铝离子[2]和氨基催化[3]过程中的使用。在胺离子催化反应中，咪唑烷酮结构（方案1）已成为一种优越的催化剂支架咪唑烷酮1已被用于加速[4+ 2]、[5][3+ 2]、[6]和[4+ 3][7]环加成以及吡咯[8]与α， β-不饱和醛的共轭加成。戊醛衍生的咪唑烷酮2已被用于吲哚[9]和富电子芳烃[10]的共轭加成以形成新的CÀC键，氮-[11]和氢化物基的亲核试剂[12]的加成以及分子内[4+ 2]环加成[13]咪唑烷酮3已用于离子催化的Diels-Alder环加成[14]和α， β-不饱和酮的共轭还原[15]反应。在Diels-Alder使用1·HCl催化剂的环加成反应的最初出版物中指出，水在反应中具有双重作用，既提高了产物的产率，又提高了产物的ee。[5a]这些观察结果还有待通过实验结果来解释。在随后使用催化剂1-3[5-15]的报告中，大多数优化的反应条件涉及在反应介质（水、异丙醇或乙醇）中使用质子溶剂。从实际的角度来看，在不严格排除水分的情况下进行这些转换的能力使其操作简单，无疑在该领域的快速发展中发挥了重要作用。先前已经报道了咪唑烷酮支架的反应性和催化剂活性的改进，并且实验证据表明，在铝离子催化转化中，选择性和动力学谱的合理化也受到了关注。[17-19]然而，到目前为止，质子溶剂在影响铝离子催化过程结果中的确切作用还没有经过严格的实验检验。本文报道了质子溶剂在咪唑烷酮1·HCl催化Diels-Alder环加成反应速率和立体化学结果中的微妙作用。作为本研究的起点，我们证实并进一步举例说明了在咪唑烷酮1·HCl催化下肉桂醛(7)与环戊二烯在一系列溶剂中的Diels-Alder环加成反应中，水对立体化学结果和产率的影响（表1）。最初的报告中没有明确包括这些数据。[5a]在无水甲醇中，环戊二烯和肉桂醛(7)之间的Diels-Alder反应分别产生了93% ee和91% ee的内加和外加物（产率88%）（表1，入口2）。在甲醇/水体系中获得了类似水平的不对称诱导，但产率更高（entry1; 93% ee endo, 93% ee exo， 93%产率）。因此，水的加入增加了所得的产率，但并不实质上改变醇的选择性
Over the past decade, organocatalysis has caught the imagination of synthetic chemists, advancing the boundaries of chemical synthesis.[1] Of particular note is the use of secondary amines in iminium ion [2] and enamine-catalyzed [3] processes. Within iminium ion catalyzed reactions the imidazolidinone architecture (Scheme 1) has emerged as a privileged catalyst scaffold.[4] Imidazolidinone 1 has been used in the acceleration of [4+ 2],[5][3+ 2],[6] and [4+ 3][7] cycloadditions as well as the conjugate addition of pyrroles [8] to α, β-unsaturated aldehydes. The pivaldehyde-derived imidazolidinone 2 has been used for the conjugate addition of indoles [9] and electron-rich aromatics [10] to form new CÀC bonds, the addition of nitrogen-[11] and hydride-based [12] nucleophiles and for intramolecular [4+ 2] cycloadditions.[13] Imidazolidinone 3 has been used in iminium ion catalyzed Diels–Alder cycloaddition [14] and conjugate reduction [15] reactions of α, β-unsaturated ketones. In the initial publication on the Diels–Alder cycloaddition using catalyst 1· HCl it was noted that water had a dual role in the reaction, increasing both yield and ee obtained for the products.[5a] These observations have yet to be explained through experimental findings. In subsequent reports using catalysts 1–3 [5–15] the majority of optimized reaction conditions involve use of a protic solvent in the reaction medium (water, isopropyl alcohol, or ethanol). From a practical perspective, the ability to perform these transformations without the rigorous exclusion of moisture makes them operationally simple and has undoubtedly been instrumental in the rapid development of the field. Investigations focussing on the reactivity of the imidazolidinone scaffold and improvements in catalyst activity have been previously reported [16] and experimental evidence to rationalize selectivities and kinetic profiles in iminium ion catalyzed transformations have also received attention.[17–19] However, to date the precise role of protic solvents in affecting the outcome of an iminium ion catalyzed process has yet to be rigorously examined experimentally. Here we report on the subtle roles of protic solvents in determining the rate and stereochemical outcome of the Diels–Alder cycloaddition catalyzed by imidazolidinone 1· HCl. As a starting point to this investigation we confirmed and further exemplified the effect of water on the stereochemical outcome and yield in the Diels–Alder cycloaddition between cinnamaldehyde (7) and cyclopentadiene catalyzed by imidazolidinone 1· HCl in a series of solvents (Table 1). This data was not explicitly included in the initial report.[5a]In anhydrous methanol the Diels–Alder reaction between cyclopentadiene and cinnamaldehyde (7) provided the endo and exo adducts in 93% ee and 91% ee, respectively (88% yield)(Table 1, entry 2). Similar levels of asymmetric induction but higher yield were obtained in a methanol/water system (entry1; 93% ee endo, 93% ee exo, 93% yield). Addition of water therefore increases the yield obtained but does not substantially alter selectivities in an alcoholic
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亚胺离子催化：在 Diels-Alder 反应加速中使用 α 效应可用电子补充信息 (ESI)：1H NMR、13C NMR、IR 和 MS 谱请参见 http://www.rsc.org/suppdata/。抄送/b2/b212239a/
DOI：
--
发表时间：
2003
期刊：
影响因子：
--
作者：
J. Cavill;J. Peters;N. Tomkinson
通讯作者：
N. Tomkinson
5-苄基咪唑烷-4-酮衍生物的实验和理论构象分析——研究有机催化中分散相互作用和“挡风玻璃雨刷”效应的“游乐场”
DOI：
--
发表时间：
2010
期刊：
影响因子：
--
作者：
D. Seebach;Uroš Grošelj;W. Schweizer;S. Grimme;Christian Mück‐Lichtenfeld
通讯作者：
Christian Mück‐Lichtenfeld
电反应 α,β-ungesättigter Iminiumionen
影响因子：
--
作者：
Sami Lakhdar;Takahiro Tokuyasu;Herbert Mayr
通讯作者：
Herbert Mayr
影响因子：
5.2
作者：
Brazier, John B.;Evans, Gareth;Tomkinson, Nicholas C. O.
通讯作者：
Tomkinson, Nicholas C. O.
影响因子：
1.8
作者：
Groselj, Uros;Schweizer, W. Bernd;Seebach, Dieter
通讯作者：
Seebach, Dieter