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首页> 外文期刊>Chemistry: A European journal >Asymmetric Iminium Ion Catalysis with a Novel Bifunctional Primary Amine Thiourea: Controlling Adjacent Quaternary and Tertiary Stereocenters
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Asymmetric Iminium Ion Catalysis with a Novel Bifunctional Primary Amine Thiourea: Controlling Adjacent Quaternary and Tertiary Stereocenters

机译：新型双功能伯胺硫脲的不对称亚胺离子催化：控制相邻的第四级和第三级立体中心

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摘要

The development of novel and highly enantioselective transformations is one of the most exciting goals for organic chemists involved in the competitive and stimulating field of asymmetric organocatalysis.~[1] In this area, the remarkable advances in the application of chiral secondary amine catalysts (asymmetric aminocatalysis)~[2a,b] are linked with the accessibility of divergent carbonyl activation modes, through either nucleophilic enamine[~2c] or dienamine~[2e] intermediates, electrophilic iminium ions~[2d] or even radical~[2f] intermediates. In particular, the incredibly high efficiency and generality demonstrated by some “privileged” organocatalysts such as proline~[3a] (I) or the synthetic MacMillan imid-CHTUNGTRENUNGazACHTUNGTRENUNGolidinones~[2d] (II) and the silyl-protected diarylprolinols catalysts~[3b] (III) (Scheme 1) have consolidated asymmetric aminocatalysis as a reliable and powerful synthetic tool for the chemo- and enantioselective functionalization of carbonyl compounds.~[2] These general and readily available catalysts represent an important starting point for the investigations of new asymmetric processes because they often avoid the need for multiple screening processes of catalysts to determine the optimal reaction conditions. However, because aminocatalysis may face problems of increasing complexity and diversity, the privileged catalysts might not always be the best candidates to solve some specific and challenging tasks (Scheme 1). In this context, the stereocontrolled conjugate addition of prochiral trisubstituted carbon nucleophiles to α,β-unsaturated aldehydes through iminium activation still represents a daunting synthetic challenge~[4] because the privileged catalysts generally allow the formation of products with high enantioselectivity but with poor diastereocontrol.~[5]
机译：对于参与不对称有机催化的竞争和刺激领域的有机化学家来说，开发新颖且高度对映选择性的转化是最令人兴奋的目标之一。[1]在这一领域，手性仲胺催化剂（不对称）的应用取得了显着进展。氨基催化）〜[2a，b]通过亲核烯胺[〜2c]或二烯胺〜[2e]中间体，亲电子亚胺离子〜[2d]或自由基〜[2f]中间体与不同羰基活化方式的可及性相关。 。尤其是，某些“特权”有机催化剂，例如脯氨酸〜[3a]（I）或合成的MacMillan酰亚胺-CHTUNGTRENUNGazazTUNGTRENUNGolidinones〜[2d]（II）和甲硅烷基保护的二芳基脯氨醇催化剂〜[3b]，显示出令人难以置信的高效率和通用性]（III）（方案1）具有巩固的不对称氨基催化作用，是羰基化合物化学和对映选择性官能化的可靠而强大的合成工具。〜[2]这些通用且容易获得的催化剂代表了研究新化合物的重要起点。非对称工艺，因为它们通常避免了为确定最佳反应条件而对催化剂进行多次筛选的需求。但是，由于氨基催化可能面临复杂性和多样性日益增加的问题，因此特权催化剂可能不一定总是是解决某些特定挑战性任务的最佳人选（方案1）。在这种情况下，通过亚胺基活化将前手性三取代碳亲核体立体控制地共轭加成到α，β-不饱和醛上仍然是一个艰巨的合成挑战[4]，因为特权的催化剂通常允许形成高对映选择性但差的非对映控制性的产物。 。〜[5]

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