分会

第十二分会：元素/金属有机

摘要

由易烯醇化的不饱和羰基化合物制备或原位生成的二烯醇类化合物是构建众多潜在生物活性分子的强有力的合成子。与普遍报道的γ-加成反应相比，α支链β,γ-不饱和醛的α-加成反应对底物的限制更少，难点在于破坏π-π共轭，面临更大的空间位阻，因此二烯醇类和亚胺之间的α-Mannich反应鲜有报道[1]。本文实现了第一例吲哚基酮亚胺与α-、β-或γ-支链的β,γ不饱和醛的高非对映选择性和对映体选择性的Mannich反应，合成了一系列具有邻位多取代立体中心的手性α季烯丙基醛和高烯丙醇。在手性双氮氧/Sc III催化剂的作用下，环氧乙烯醚和亚胺的α重排中间体之间的α-Mannich反应的区域选择性以及非对映选择性和对映选择性可以得到有效控制。实验研究和密度泛函理论计算表明，配体的大空间位阻和亚胺的Boc(叔丁氧基)保护基团是影响α区域选择性的关键因素[2]。 关键词：Meinwald重排；α-区域选择性；手性双氮氧 参考文献 [1] J. X. Xu, Y. J. Song, J. He, L. L. Li, X. M. Feng, Angew. Chem. Int. Ed.2021,133,14642–14648. [2] J. X. Xu, Y. J. Song, J. Yang, B. Q. Yang, Z. S. Su, L. L. Li, X. M. Feng, Angew. Chem. Int. Ed. 2023, 62. e202217887. Sterically Hindered and Deconjugative α-Regioselective Asymmetric Mannich Reaction of Meinwald Rearrangement-Intermediate Jinxiu Xu 1, Yanji Song1, Jia Yang1, Bingqian Yang1, Zhishan Su1, Lili Lin1,*, Xiaoming Feng1,* 1Department of Chemistry, University of Sichuan, No.24 in South section of First ring road, Chengdu, 610064 Compared to γ-addition, the α-addition of α-branched β, γ-unsaturated aldehydes faces larger steric hindrance and disrupts the π–π conjugation, which might be why very few examples are reported. In this article, a highly diastereo- and enantioselective α-regioselective Mannich reaction of isatin-derived ketimines with α-, β- or γ-branched β, γ-unsaturated aldehydes, generated in situ from Meinwald rearrangement of vinyl epoxides, is realized by using chiral N,N’-dioxide/Sc III catalysts. A series of chiral α-quaternary allyl aldehydes and homoallylic alcohols with vicinal multisubstituted stereocenters are constructed in excellent yields, good d.r. and excellent ee values. Experimental studies and DFT (density functional theory) calculations reveal that the large steric hindrance of the ligand and the Boc (tButyloxy carbonyl) protecting group of imines are critical factors for the α-regioselectivity.

关键词

α-区域选择性

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