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手性双环咪唑催化剂的设计、合成与应用。

Design, Synthesis, and Application of Chiral Bicyclic Imidazole Catalysts.

出版信息

Acc Chem Res. 2022 Sep 20;55(18):2708-2727. doi: 10.1021/acs.accounts.2c00455. Epub 2022 Aug 31.

Abstract

Asymmetric organocatalysis has been considered to be an efficient and reliable strategy for the stereoselective preparation of optically active chemicals. In particular, chiral tertiary amines as Lewis base organocatalysts bearing core structures including quinuclidine, dimethylaminopyridine (DMAP), -methylimidazole (NMI), amidine, etc. have provided new and powerful tools for various chemical transformations. However, due to the limitations in structural complexity, synthetic difficulty, low catalytic efficiency, and high cost, the industrial application of such catalysts is still far from being widely adopted. Therefore, the development of new chiral tertiary amine catalysts with higher activity and selectivity is greatly desired.In order to address the contradiction between activity and selectivity caused by the group, a bicyclic imidazole structure bearing a relatively large bond angle ∠θ was designed as the skeleton of our new catalysts. 6,7-Dihydro-5-pyrrolo[1,2-]imidazole (abbreviated as DPI) and 5,6,7,8-tetrahydroimidazo[1,2-]pyridine (abbreviated as TIP) are two of the utilized skeletons. In addition to obtaining satisfactory catalytic activity, excellent enantioselectivity would also be expected because the stereocontrol R group is neither far nor close to the catalytic active site (sp- atom) and is adjustable. Based on this skeleton, a family of chiral bicyclic imidazole catalysts were easily prepared and successfully applied in several enantioselective reactions for the synthesis of a variety of valuable chiral compounds.6,7-Dihydro-5-pyrrolo[1,2-]imidazole (abbreviated as DPI) is the predominantly utilized skeleton. First, HO-DPI, the key intermediate of the designed chiral bicyclic imidazole catalysts, could be efficiently synthesized from imidazole and acrolein, then separated by kinetic resolution or optical resolution. Second, Alkoxy-DPI, the alkyloxy-substituted chiral bicyclic imidazole catalysts, were synthesized by a one-step alkylation from HO-DPI. This type of catalyst has been successfully applied in asymmetric Steglich rearrangement (-acylation rearrangement of -acylated azlactones), asymmetric phosphorylation of lactams, and a sequential four-step acylation reaction. Third, Acyloxy-DPI, the acyloxy-substituted chiral bicyclic imidazole catalysts, were synthesized with a one-step acetylative kinetic resolution from racemic HO-DPI or acylation from enantiopure HO-DPI. The catalyst AcO-DPI has been successfully applied in enantioselective Black rearrangement and in direct enantioselective -acylation of 3-substituted benzofuran-2(3)-ones and 2-oxindoles. Fourth, Alkyl-DPI was synthesized via a two-step reaction from racemic HO-DPI and separated easily by resolution. The catalyst Cy-DPI has been successfully applied in dynamic kinetic resolution of 3-hydroxyphthalides through enantioselective -acylation. Cy-PDPI was synthesized through a Cu-catalyzed amidation from Cy-DPI and successfully applied in the kinetic resolution of secondary alcohols with good to excellent enantioselectivities. Finally, the carbamate type chiral bicyclic imidazole catalysts, Carbamate-DPI, were readily synthesized from HO-DPI, and the catalyst Ad-DPI bearing a bulky adamantyl group was successfully applied in the synthesis of the anti-COVID-19 drug remdesivir via asymmetric phosphorylation. Alongside our initial work, this Account also introduces four elegant studies by other groups concerning asymmetric phosphorylation utilizing chiral bicyclic imidazole catalysts.In summary, this Account focuses on the chiral bicyclic imidazole catalysts developed in our group and provides an overview on their design, synthesis, and application that will serve as inspiration for the exploration of new organocatalysts and related reactions.

摘要

作为一种有效的立体选择性制备光学活性化学品的策略,不对称有机催化已经得到了广泛的关注。特别是,手性叔胺作为路易斯碱有机催化剂,具有包括喹诺啉、二甲基氨基吡啶(DMAP)、-甲基咪唑(NMI)、脒等核心结构,为各种化学转化提供了新的有力工具。然而,由于结构复杂性、合成难度、催化效率低和成本高等限制,这些催化剂的工业应用仍然远远没有得到广泛采用。因此,开发具有更高活性和选择性的新型手性叔胺催化剂是非常需要的。

为了解决由基团引起的活性和选择性之间的矛盾,我们设计了一种具有较大键角∠θ的双环咪唑骨架作为我们新催化剂的骨架。6,7-二氢-5-吡咯并[1,2-]咪唑(简称 DPI)和 5,6,7,8-四氢咪唑并[1,2-]吡啶(简称 TIP)是两种被利用的骨架。除了获得令人满意的催化活性外,由于立体控制 R 基团既不远离也不靠近催化活性位点(sp 原子),并且是可调节的,因此还可以预期获得优异的对映选择性。基于这个骨架,我们很容易制备了一系列手性双环咪唑催化剂,并成功地应用于几种对映选择性反应中,用于合成各种有价值的手性化合物。

6,7-二氢-5-吡咯并[1,2-]咪唑(简称 DPI)是主要使用的骨架。首先,从咪唑和丙烯醛高效合成设计的手性双环咪唑催化剂的关键中间体 HO-DPI,然后通过动力学拆分或光学拆分进行分离。其次,通过 HO-DPI 的一步烷基化合成烷氧基-DPI,这是一种烷氧基取代的手性双环咪唑催化剂。这种催化剂已成功应用于不对称 Steglich 重排(-酰化重排)、内酰胺的不对称磷酸化和四步连续酰化反应。第三,通过对映体纯 HO-DPI 的酰化或从外消旋 HO-DPI 的乙酰化动力学拆分,合成了酰氧基-DPI,这是一种酰氧基取代的手性双环咪唑催化剂。催化剂 AcO-DPI 已成功应用于对映选择性 Black 重排和 3-取代苯并呋喃-2(3)-酮和 2-氧吲哚的直接对映选择性酰化。第四,通过外消旋 HO-DPI 的两步反应合成烷基-DPI,并通过拆分很容易分离。催化剂 Cy-DPI 已成功应用于 3-羟基邻苯二甲酸酐的动力学拆分通过对映选择性酰化。通过 Cy-DPI 的铜催化酰胺化合成 Cy-PDPI,并成功应用于仲醇的动力学拆分,具有良好到优异的对映选择性。最后,通过 HO-DPI 很容易合成了氨基甲酸酯型手性双环咪唑催化剂 Carbamate-DPI,并且带有大金刚烷基的催化剂 Ad-DPI 已成功应用于通过不对称磷酸化合成抗 COVID-19 药物瑞德西韦。除了我们的初步工作外,本帐户还介绍了其他四个关于利用手性双环咪唑催化剂进行不对称磷酸化的优雅研究。

总之,本帐户重点介绍了我们小组开发的手性双环咪唑催化剂,并提供了它们的设计、合成和应用的概述,这将为探索新的有机催化剂和相关反应提供灵感。

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