分會

第十二分會：元素/金屬有機

摘要

由易烯醇化的不飽和羰基化合物制備或原位生成的二烯醇類化合物是構(gòu)建眾多潛在生物活性分子的強有力的合成子。與普遍報道的γ-加成反應相比，α支鏈β,γ-不飽和醛的α-加成反應對底物的限制更少，難點在于破壞π-π共軛，面臨更大的空間位阻，因此二烯醇類和亞胺之間的α-Mannich反應鮮有報道[1]。本文實現(xiàn)了第一例吲哚基酮亞胺與α-、β-或γ-支鏈的β,γ不飽和醛的高非對映選擇性和對映體選擇性的Mannich反應，合成了一系列具有鄰位多取代立體中心的手性α季烯丙基醛和高烯丙醇。在手性雙氮氧/Sc III催化劑的作用下，環(huán)氧乙烯醚和亞胺的α重排中間體之間的α-Mannich反應的區(qū)域選擇性以及非對映選擇性和對映選擇性可以得到有效控制。實驗研究和密度泛函理論計算表明，配體的大空間位阻和亞胺的Boc(叔丁氧基)保護基團是影響α區(qū)域選擇性的關(guān)鍵因素[2]。 關(guān)鍵詞：Meinwald重排；α-區(qū)域選擇性；手性雙氮氧 參考文獻 [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.

關(guān)鍵詞

α-區(qū)域選擇性

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