摘要：苄基C-H键氧化在C-H键活化中发挥了重要作用。在氧化产物中，芳基酮被认为是天然产物，活性药物成分，农用化学品和其他复杂有机分子合成的关键结构基元和有用的前体。

苄基C-H键热力学强且化学惰性；因此，他们的直接激活是困难的。用于苄基C-H键氧合的经典氧化方法需要有毒和昂贵的试剂作为苛刻条件下的催化剂或强氧化剂。然而，由于其三重态基态，双氧在温和条件下直接是对于苄基C-H键的氧化反应的非反应性氧化剂。因此，用双氧作为末端氧化剂的直接苄基C-H键活化仍然是主要挑战。在可见光照射下用分子氧光催化活化碳氢化合物是相对于结构复杂，合成步骤繁琐，价格昂贵的传统催化策略的原子经济和环境友好的替代方法。

在温和的反应条件下，我们开发了一种绿色高效的由核黄素四乙酸脂(RFT)，N-羟基琥珀酰亚胺(NHS)和FeCl3·6H2O组成的协同光催化体系，用于可见光催化苄基C-H键氧化的方法。与之前关于使用黄素作为光催化剂的C-H键激活的程序相比，我们使用廉价的三氯化铁和NHS代替昂贵的三氟甲磺酸钪或仿生非血红素铁络合物，进一步扩大了底物范围。 此外，我们还提出了该光催化体系中C-H键氧化的可能的自由基机理。

关键词：苄基C-H键氧化；核黄素四乙酸酯；可见光；N-羟基琥珀酰亚胺

Visible Light-Driven Riboflavin Tetraacetate Catalyzes the Oxidation of benzyl C-H Bonds

Abstract: The oxidation of  benzylic C-H bonds systems have played a prominent role in C-H bond activation. Among the oxidation products, Aryl ketones are recognized as key structural motifs and useful precursors for synthesis of natural products, active pharmaceutical ingredients, agrochemicals and other complicated organic molecules.

 Benzylic C−H bond is thermodynamically strong and chemically inert; thus, their direct activation is difficult. Classical oxidation methods for benzylic C−H bond oxygenation require toxic and expensive reagents as catalysts or strong oxidants under harsh conditions. However, dioxygen is directly an unreactive oxidant toward the oxidation of the benzylic C−H bonds under mild conditions due to its triplet ground state. Therefore, direct benzylic C−H bond activation with dioxygen as the terminal oxidant remains a primary challenge. The photocatalytic activation of hydrocarbons with molecular oxygen under visible light irradiation is an atomic economic and environmentally friendly alternative to complex catalytic structures, complicated synthesis steps, and expensive conventional catalytic strategies.

A green and highly efficient cooperative photocatalytic system which consists of riboflavin tetraacetate(RFT), N-Hydroxysuccinimide(NHS) and FeCl3·6H2O has been developed for C−H bond oxygenation with visible light under mild reaction conditions. Compared to the previous procedures about C−H bond activation by using flavins as photocatalyst, we use cheap ferric chloride and NHS instead of expensive scandium triflate or biomimetic non-heme iron complex, further expand the substrate scopes. In addition, a possible radical mechanism for the C−H bond oxygenation in this photocatalytic system is proposed by us.

Key Words: benzylic C-H bonds oxidation; RFT; visible light; NHS

目录

1 引言 1

1.1 核黄素的简介 1

1.2 研究内容及创新点 1

1.3 文献综述 2

1.3.1 可见光驱动黄素催化苄醇氧化 3

1.3.2 可见光驱动RFT协同光催化苄基C-H键氧化 6

2 实验部分