CO2Chem - Redox-Neutral Photocatalytic CH Carboxylation of Hydrocarbons with CO2

近年来，人们在通过技术过程模拟生物光合作用方面做出了巨大努力，目的是将太阳能转化为化学储存的能量。在这样的方法中产生的富含能量的分子通常是来自作为费-托方法的进料的二氧化碳或合成气（H2/CO）的还原的二氢、甲烷或甲醇。相比之下，使用二氧化碳的太阳能驱动的有价值化学品合成仍处于非常早期的发展阶段。到目前为止，二氧化碳仅在很小程度上用作化学合成的原材料，但聚合物生产的工业项目已显示出该方法的可行性和可持续性。本项目旨在为饱和烃与二氧化碳的光化学、氧化还原中性C-H羧化反应开发合成和机理基础。我们的初步数据清楚地表明，二氧化碳是一个有价值的试剂在官能化的C-H键，其中二氧化碳是正式插入到碳氢键。芳烃、苯乙烯以及苄基或α-羰基C-H键的氧化还原中性羧化反应已经实现。所开发的方法是非常有价值的，并证明在合成药物分子，如布洛芬，从简单的芳烃前体和二氧化碳的有用。然而，应该清楚地指出，现有的两种方法都排除了使用最丰富的非活化C（sp3）-H键。为了应对这一挑战，我们提出了新的合成策略的基础上光催化产生的烷基自由基和地球丰富的金属络合物，以提供C-H羧化在一个整体的氧化还原中性的过程。申请人在钴催化和加氢裂化方面的综合经验将用于建立将非活性脂族烃转化为具有二氧化碳作为C1合成子的官能化化学品的方法。

Recent years have seen large efforts in mimicking biological photosynthesis by technical processes with the goal of converting solar energy into chemically stored energy. The energy-rich molecules produced in such processes are typically dihydrogen, methane or methanol from the reduction of carbon dioxide or syngas (H2/CO) as feed for the Fischer-Tropsch process. In contrast, the solar-driven synthesis of valuable chemicals using carbon dioxide is still at a very early stage of development. So far, carbon dioxide is only used to a small extent as a raw material in chemical synthesis, but industrial projects in polymer production have shown the feasibility and sustainability of the approach. This project aims to develop the synthetic and mechanistic basis for the photochemical, redox-neutral C-H carboxylation of saturated hydrocarbons with carbon dioxide. Our preliminary data clearly show that carbon dioxide is a valuable reagent in functionalizations of C-H bonds in which carbon dioxide is formally inserted into the carbon hydrogen bond. The redox neutral carboxylation of arenes, styrenes as well as benzylic or α-carbonyl C-H bonds was already realized. The developed methods are highly valuable and proved useful in the synthesis of drug molecules, such as ibuprofen, from simple arene precursors and carbon dioxide. It should be clearly stated, however, that both existing methods preclude the use of the most abundant, non-activated C(sp3)-H bonds. In order to address this challenge, we propose new synthetic strategies based on photocatalytically generated alkyl radicals and earth-abundant metal complexes to provide C-H carboxylation in an overall redox-neutral process. The combined experience of the applicants in cobalt-catalysis and photocatalysis will be used to establish methodologies for the conversion of non-activated aliphatic hydrocarbons into functionalized chemicals with carbon dioxide as a C1 synthon.