Highly enantio- and regioselective quinone Diels-Alder reactions catalyzed by a tridentate [(Schiff base)CrIII] complex
Highly enantio- and regioselective quinone Diels-Alder reactions catalyzed by a tridentate [(Schiff base)CrIII] complex
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DOI：
10.1002/anie.200502176
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发表时间：
2005-01-01
影响因子：
16.6
通讯作者：
Jacobsen, EN
中科院分区：
文献类型：
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作者：
Jarvo, ER;Lawrence, BM;Jacobsen, EN
八珊瑚 Pseudopterogorgia elisabethae 产生多种萜类化合物，例如 colombiasin A、elisapterosin B 和 elisabethin A，显示出不同的结构框架和生物活性。 [1]这些次生代谢物可能源自相对简单的常见生物合成前体；事实上，诸如 1 之类的化合物可以通过不同的环化途径转化为更复杂的多环天然产物，已从同一生物体中分离出来。 [2]我们对开发高效醌狄尔斯-阿尔德 (qDA) 催化剂产生兴趣，用于制备与 1 [例如 2，方程 (1)] 相关的中间体，作为合成该天然产物家族的统一仿生策略的一部分。在此，我们报告了一种由新型单体 [(希夫碱) Criiii] 络合物催化醌与各种二烯进行高度对映选择性 qDA 反应的新方法。 [3]在本期的下一篇论文中，我们描述了在关键步骤中采用该方法的 (À)-colombiasinA 和 (À)-elisapterosinB 的简明不对称催化合成。 [4]醌与二烯的反应是 Diels 和 Alder 认识的第一类环加成途径，[5] 从那时起，它在有机合成中得到了广泛的应用。 [6]然而，直到最近，对映选择性 qDA 反应的有效催化剂仍然难以捉摸。在 Mikami 及其同事的开创性研究中，发现二元钛配合物对有限范围的底物有效。[7, 8] 随后，Evans 和同事报道了双（恶唑啉）-镧系元素配合物作为不对称催化剂，用于甲基取代二烯与能够进行两点结合的酯取代醌的反应。[9] Corey 和同事描述了使用阳离子 oxazaborilidines 作为对映选择性 qDA 催化剂，通过单点结合促进环加成，不对称醌通过激活最路易斯碱性的羰基进行反应。 [10]尽管取得了这些重要进展，但鉴定具有广泛底物范围的新型高活性 qDA 催化剂仍然是一个重要目标，特别是在生物活性化合物合成中获取感兴趣的环加合物的多样性。我们自己的催化剂开发研究最初侧重于醌 3 和二烯 4 的反应，这是一个与 colombiasinA 相关的模型，旨在测量催化剂的对映选择性和区域选择性（方案 1）。作为
The octocoral Pseudopterogorgia elisabethae produces a variety of terpenoids, such as colombiasin A, elisapterosin B, and elisabethin A, that display diverse structural frameworks and bioactivities.[1] These secondary metabolites are possibly derived from a relatively simple common biosynthetic precursor; indeed, compounds such as 1, which could undergo transformation to the more complex polycyclic natural products by divergent cyclization pathways, have been isolated from the same organism.[2] We became interested in developing efficient quinone Diels–Alder (qDA) catalysts for the preparation of intermediates related to 1 [eg 2, Eq.(1)] as part of a unified biomimetic strategy for the syntheses of this family of natural products. Herein, we report a new method for highly enantioselective qDA reactions of quinones with a variety of dienes catalyzed by a new, monomeric [(Schiff base) Criii] complex.[3] In the following paper in this issue, we describe concise asymmetric catalytic syntheses of (À)-colombiasinA and (À)-elisapterosinB employing this methodology in the pivotal step.[4] The reaction of quinones with dienes was the first class of cycloaddition pathways to be recognized by Diels and Alder,[5] and it has enjoyed widespread use in organic synthesis ever since.[6] However, until recently, effective catalysts for enantioselective qDA reactions have remained elusive. In seminal studies by Mikami and co-workers, Ti–binolate complexes were found to be effective for a limited range of substrates.[7, 8] Subsequently, Evans and co-workers reported bis (oxazoline)–lanthanide complexes as asymmetric catalysts for reactions of methyl-substituted dienes with estersubstituted quinones capable of two-point binding.[9] Corey and co-workers described the use of cationic oxazaborilidines as enantioselective qDA catalysts that promote cycloaddition through single-point binding, with unsymmetrical quinones undergoing reaction by activation of the most Lewis basic carbonyl group.[10] Despite these important advances, identification of new and highly active qDA catalysts with broad substrate scope remains an important goal, particularly for accessing the diversity of cycloadducts of interest in the synthesis of biologically active compounds. Our own catalyst development studies focused initially on the reaction of quinone 3 and diene 4, a model relevant to the colombiasinA effort and designed to gauge both catalyst enantioselectivity and regioselectivity (Scheme1). As the