Highly diastereo- and enantioselective direct aldol reactions in water
Highly diastereo- and enantioselective direct aldol reactions in water
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DOI：
10.1002/anie.200502488
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发表时间：
2006-01-01
影响因子：
16.6
通讯作者：
Shoji, M
中科院分区：
文献类型：
--
作者：
Hayashi, Y;Sumiya, T;Shoji, M
重要性：硅氧基脯氨酸催化剂已被确定为用于在水中不使用有机溶剂的对映选择性直接羟醛缩合反应的有效催化剂。当催化剂1的质量分数为10mol%时，对芳香醛和脂肪醛的对映选择性均大于95%，反选择性为4.7：1-25：1。这些选择性高于在有机溶剂中进行的反应。催化剂的负载量可以降低到1摩尔%，并且还报道了使用无环酮代替环己酮。评论：水是一种环境友好的介质，它避免了有机溶剂固有的污染问题。乙酰基脯氨酸催化剂在水中进行合成有用的直接不对称羟醛缩合反应的有效性是由于它们在水中的部分溶解度。催化剂与醛和酮形成有机相，其中羟醛缩合反应有效地进行。催化剂1可以由市售的反式羟脯氨酸一步容易地制备。催化剂1的简单制备和高效率为未来在水中有效的有机催化剂的设计提供了有趣的前景。对于在水中的对映选择性直接羟醛缩合反应的相关报道，参见：CF Barbas III等人，J. Am. 2006，128，734-735中所述。
Significance: Siloxyproline catalysts have been identified as effective catalysts for the enantioselective direct aldol reaction in water without using an organic solvent. With 10 mol% of catalyst 1, excellent enantioselectivities (over 95%) and anti selectivities (dr= 4.7: 1–25: 1) are obtained with different aromatic and aliphatic aldehydes. These selectivities are higher than for the reaction performed in organic solvents. Catalyst loadings can be reduced to 1 mol% and the use of acyclic ketones instead of cyclohexanone is also reported.Comment: Water is an environmentally friendly medium, which avoids the problems of pollution that are inherent with organic solvents. The effectiveness of the siloxyproline catalysts to carry out the synthetically useful direct asymmetric aldol reaction in water is due to their partial solubility in water. The catalyst forms an organic phase with the aldehyde and ketone in which the aldol reaction proceeds efficiently. Catalyst 1 can be easily prepared form commercially available trans-hydroxyproline in one step. The simple preparation and high efficiency of catalyst 1 provides interesting prospects for the design of future organocatalysts effective in water. For a related report of enantioselective direct aldol reaction in water, see: CF Barbas III et al. J. Am. Chem. Soc. 2006, 128, 734-735.