Novel bifunctional chiral urea and thiourea derivatives as organocatalysts:: Enantioselective nitro-Michael reaction of malonates and diketones
Novel bifunctional chiral urea and thiourea derivatives as organocatalysts:: Enantioselective nitro-Michael reaction of malonates and diketones
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DOI：
10.1002/chem.200800633
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发表时间：
2008-01-01
影响因子：
4.3
通讯作者：
Pedrosa, Rafael
中科院分区：
文献类型：
--
作者：
Andres, Jose M.;Manzano, Ruben;Pedrosa, Rafael
手性氢键供体催化有用的对映选择性转化的能力构成了越来越多的感兴趣的领域，并且为此目的已经描述了不同类型的结构。[1]一类重要的物质是脲和硫脲化合物[2]，它们经常用于几种转化，如亨利或氮杂亨利，[3]曼尼希，[4]斯特雷克，[5]和弗里德尔-克拉夫茨[6]反应或迈克尔[7]和硝基迈克尔[8]加成。这些类型的催化剂的模块化设计需要引入不同的脲和硫脲部分的可能性和结构的手性信息的修改。迄今为止，大多数所描述的催化剂是具有吸电子基团的芳基或二芳基脲或硫脲，尽管一些相对富电子的衍生物已被证明催化各种对映选择性转化。[9]催化剂中的手性信息被置于脲或硫脲中的氮末端或中心手性核中。在这方面，一些结构用于制备催化剂，即手性二胺，[10]反式环己烷-1，2-二胺的两种对映体，[10，11]联萘胺，[12]衍生自金鸡纳生物碱的二胺，[13]氨基醇，[14]以及最近的糖。[15]在我们看来，开发新的手性支架纳入脲和硫脲衍生物，能够作为双功能有机催化剂，是必要的。因为，一般来说，1，2-二胺是导致最佳结果的结构，所以我们计划考虑三个事实来制备这些化合物：i）起始材料将是可商购的且便宜的; ii）胺的两种对映异构体必须是可获得的;以及iii）胺的对映异构体是可商购的且便宜的。
The ability of chiral hydrogen-bond donors to catalyze useful enantioselective transformations constitutes an increasing area of interest, and diverse types of structures have been described to this end.[1] An important class of species are urea and thiourea compounds [2] which have frequently been used in several transformations, such as Henry or aza-Henry,[3] Mannich,[4] Strecker,[5] and Friedel–Crafts [6] reactions or Michael [7] and nitro-Michael [8] additions. The modular design of these types of catalysts requires the possibility to introduce different urea and thiourea moieties and the modification of the structure with the chiral information. Most of the described catalysts until now are aryl or diaryl ureas or thioureas with electron withdrawing groups, although some relatively electron rich derivatives have proved to catalyze a variety of enantioselective transformations.[9]The chiral information in the catalyst has been placed at both the nitrogen terminus in the urea or thiourea or in the central chiral core. In this respect, a few structures are used in the preparation of the catalysts, namely chiral diamines,[10] both enantiomers of trans cyclohexane-1, 2-diamine,[10, 11] binaphthylamines,[12] diamines derived from cinchona alkaloids,[13] amino alcohols,[14] and very recently, sugars.[15] In our opinion, the development of novel chiral scaffolds to be incorporated into urea and thiourea derivatives, capable to act as bifunctional organocatalyts, is necessary. Because, in general, 1, 2-diamines are the structures that lead to the best results, we planned to prepare these compounds taking into account three facts: i) The starting material would have be commercially available and cheap; ii) both enantiomers of the amine must be accessible; and iii) the