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Radical redox catalysis by Ti complexes

Ti配合物的自由基氧化还原催化

基本信息

批准号：
10798749
负责人：
Song Lin
金额：
$ 15.65万
依托单位：
CORNELL UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2020
资助国家：
美国
起止时间：
2020-04-01 至 2024-06-30
项目状态：
已结题

项目摘要

Project Summary This proposal focuses on uncovering new radical-based methodologies that facilitate the synthesis of bioactive compounds. Organic radicals are highly reactive species with unique chemoselectivities that complement canonical two-electron chemistry. Recently, the emergence of new reaction strategies that leverage single-electron redox events and harness radical intermediates for the selective functionalization of organic molecules has provided chemists with useful tools for solving contemporary synthetic problems. However, the highly reactive nature of many organic radicals has made it difficult to impart catalyst-control over the regio- and stereoselectivity of these fleeting intermediates, especially when complex reaction systems are concerned. In particular, catalytic stereoselective reactions involving free radical intermediates remain limited, and the discovery of such processes is highly desirable. To provide new radical-based platforms for reaction discovery and synthetic innovation, we developed catalytic strategies that leverage the unique redox features of low-valent Ti complexes to achieve redox-neutral and net-reductive transformations, and through catalyst innovation, we demonstrated that free-radical-mediated reactions can be made highly enantioselective. These promising results prompted us to continue to invent novel catalytic and reaction strategies that can effectively harness radical intermediates and provide powerful tools for solving a wide range of longstanding synthetic problems. In the parent proposal, we aim to build upon our previous success but move our research into new grounds. In each of the projects targeted herein, we aim to advance a new approach that employ radical-based catalysts or reagents to address a prominent challenge in organic synthesis. The transformations targeted in this grant are either currently unknown or display salient limitations in reaction scope or selectivity. Among the specific reactions that we aim to develop in the context of this grant are: enantioselective cycloadditions, enantioselective epoxide isomerizations, oxidative desymmetrization of alcohols, enantioselective ⍺-oxidation of amides, and site-selective functionalization of aliphatic C–H bonds. In addition, in-depth studies using canonical physical organic and electroanalytical techniques will provide insights into the reaction mechanisms. The development and mechanistic understanding of these proposed transformations will represent significant advances for the field of organic synthesis.

项目摘要本提案的重点是发现新的基于激进的方法，生物活性化合物有机自由基是具有独特化学选择性的高活性物质，补充正则双电子化学。最近，出现了新的反应策略，利用单电子氧化还原事件和利用自由基中间体进行选择性有机分子的功能化为化学家提供了解决当代问题的有用工具，合成问题。然而，许多有机自由基的高反应性性质使得很难将其转化为有机自由基。赋予催化剂对这些短暂中间体的区域和立体选择性的控制，特别是当涉及到复杂的反应体系时。特别是催化立体选择性反应涉及自由基中间体仍然有限，并且这些过程的发现是非常重要的。令人向往为了为反应发现和合成创新提供新的基于自由基的平台，我们开发了利用低价钛络合物独特的氧化还原特征的催化策略，实现氧化还原中性和净还原转化，并通过催化剂创新，证明了自由基介导的反应可以是高度对映选择性的。这些有希望的结果促使我们继续发明新的催化和反应策略，有效地利用自由基中间体，并提供强大的工具来解决广泛的长期存在的合成问题。在母公司提案中，我们的目标是在以前成功的基础上再接再厉，把我们的研究转移到新的领域在这里针对的每个项目中，我们的目标是推进一个新的采用基于自由基的催化剂或试剂来解决有机化学中的突出挑战的方法合成.本授权书中的目标转换要么是目前未知的，要么是突出的反应范围或选择性的限制。在我们旨在发展的具体反应中，该授权的内容是：对映选择性环加成，对映选择性环氧化物异构化，醇的氧化去对称化，酰胺的对映选择性顺式氧化，和脂肪族C-H键的官能化。此外，深入研究使用典型的物理有机而电分析技术将提供对反应机理的深入了解。发展对这些拟议的转变的机械理解将代表重大进展在有机合成领域。