超分子选择性碳氢键活化

Selective C-H bond oxidation is a great challenge in organic synthesis. By selective oxidation of C-H bonds, functional groups can be strategically incorporated at the desired positions of hydrocarbons, providing an efficient way for the synthesis of structurally diverse organic molecules. Over the decades, significant advancements have been made for selective C-H bond oxidation based on electronic, steric, and substrate-based directing factors. However, these approaches are limited by the inherent structural properties of the substrates. Thus, it remains a great interest to develop new strategies for selective C-H bond oxidation to cater for a wide diversity of substrates...Supramolecular host-guest chemistry provides a promising means to achieve selectivity in a wide range of organic reactions. Cyclodextrins (CDs) are water-soluble supramolecular compounds with hydrophobic cavity and hydrophilic surface which have been extensively employed as ideal hosts in supramolecular catalysis...Dioxiranes generated in situ from ketones and Oxone are one of the most commonly used oxidizing agents. The distinctive features of dioxiranes including excellent selectivity, tunable reactivity, and exceptional insensitivity to air/moisture reaction conditions offer remarkable advantages in effecting a wide variety of organic transformations. In addition, dioxiranes are generally robust, non-toxic and inexpensive. ..In this proposal, we plan to employ cyclodextrins as supramolecular hosts for dioxirane-based selective C-H bond oxidation in aqueous medium. We propose to synthesize novel cyclodextrins by selective modification via our newly developed gold-catalyzed three component coupling reaction and Morita-Baylis-Hillman oligosaccharide coupling reaction. We will employ native and novel cyclodextrins for selective C-H bond oxidation of cyclic aliphatic hydrocarbons, competitive oxidation of hydrocarbon mixtures, and controlled oxidation of phenols. Finally, we intend to develop an efficient photochemical approach for cyclodextrin-assisted selective C-H bond oxidation.

选择性碳氢键氧化是有机合成的重大挑战。直接选择性地断裂碳氢键，能够有效地提高反应效率和原子经济性。经过多年的努力,选择性碳氢键氧化的方法已取得重大进展，然而受底物结构的限制。超分子主-客体化学能够有效地提高有机反应的选择性。环糊精作为一种水溶性超分子化合物，具有内腔疏水外部亲水的特性，是理想的宿主分子。双环氧乙烷由酮和过硫酸氢钾复合盐制备而得到, 是一种常用的氧化剂，具有选择性强，可调控活性，对空气和水不敏感以及高效无毒，价廉的优点。在本项目中,以环糊精为超分子宿主,双环氧乙烷为氧化剂, 在室温下以水为溶剂进行选择性碳氢键氧化。并且通过金催化的三组分偶合反应和Mortia-Baylis-Hillman反应, 对环糊精进行修饰。研究环糊精及其衍生物对环状脂肪族碳氢键的选择性氧化、有机混合物的竞争性氧化,以及苯酚的控制性氧化。最后, 本课题组将研究环糊精协助进行选择性碳氢键活化的光化学。

在有机合成中，选择性氧化不活泼的碳氢键是目前面临的重大挑战之一。经过多年的努力, 基于电子因素、位阻因素和基于底物导向基团因素的选择性碳氢键氧化的方法已取得重大进展，但这些方法很大程度上仍受到底物本身的结构特质和氧化剂性质的限制。超分子主-客体化学能够有效地提高有机反应的选择性。环糊精作为一种水溶性超分子化合物，具有内腔疏水外部亲水的特性，是理想的宿主分子。Dioxirane是一种由酮和过硫酸氢钾复合盐（Oxone）制备而得到的常用氧化剂，具有选择性强，可调控活性，对空气和水不敏感以及高效无毒，价廉的优点。在本项目中，1）利用环糊精为超分子宿主, 以Oxone与酮现场生成的dioxirane为氧化剂, 在室温下以水为溶剂对各种环己烷底物进行选择性碳氢键氧化研究，；2）利用金催化的三组分偶合反应, 发展了一种简便并且高效合成具有炔丙基胺结构的β-环糊精的合成方法学；3）在研究环糊精辅助的选择性碳氢键活化的光化学研究中发展了一种有效的光氧化的酰胺键形成的方法；4）设计和合成了一系列在激发态下具有强氧化性的有机小分子染料并利用其作为光催化剂用于光氧化形成酰胺键的合成反应中。