Deep Eutectic Solvents for Simple and Sustainable Organometallic Catalysis

溶剂在合成中起着基础性的作用。不幸的是，许多常用的挥发性有机溶剂(VO)对人类和/或环境有害。一些卤化和极性非质子化溶剂，如二甲基甲酰胺、N-甲基-2-吡咯烷酮和1，2-二氯乙烷，已被归类为REACH下的“高度关注物质”。然而，寻找合适的替代品是一件具有挑战性的事情。寻找环境友好的溶剂是当前可持续化学的一个热门话题。近年来，深共晶溶剂(DES)作为一种新型的反应介质出现。DES与离子液体(ILS)有关，通常主要由离子组成。它们通常是季铵盐(如氯化胆碱)与金属盐(如氯化锌)或氢键供体(如尿素)结合而形成的共晶混合物。它们具有较低的蒸汽压，良好的热稳定性，并能够溶解一系列溶质。然而，与许多ILS不同的是，它们廉价、无毒、可生物降解，而且从潜在的可再生原料合成路线相对较短。因此，作为VOS的可持续替代品，它们具有许多理想的特性。研究表明，使用DES作为溶剂，即使在水存在的情况下，也可以发生涉及高活性有机金属试剂(如格氏试剂或烷基锂试剂)的反应。这是非常令人惊讶的，因为这些条件会迅速降解传统溶剂中的有机金属。该项目将在这些观察的基础上进一步发展新的催化反应，使用DES作为温和条件下的可持续溶剂，而不受大气湿度或氧气的保护。

Solvents play a fundamental role in synthesis. Unfortunately, many commonly used volatile organic solvents (VOS) are harmful to humans and/or the environment. Some halogenated and polar aprotic solvents such as dimethylformamide, N-Methyl-2-pyrrolidone and 1,2-dichloroethane are already categorised as "substances of very high concern" under REACH. However, suitable alternatives are challenging to find. The search for environmentally benign solvents is currently a hot topic in sustainable chemistry. Recently, deep-eutectic solvents (DES) have emerged as novel reaction media. DES are related to ionic liquids (ILs) and are usually composed predominantly of ions. They are often formed by combination of a quaternary ammonium salt (e.g. choline chloride, ChCl) with a metal salt (e.g. ZnCl2) or hydrogen-bond donor (e.g. urea) to form eutectic mixtures. They have low vapour pressures, good thermal stabilities and are able to dissolve a range of solutes. However, in contrast to many ILs, they are cheap, non-toxic, biodegradable and have relatively short synthetic routes from potentially renewable feedstocks. As such, they have many desirable characteristics as sustainable alternatives to VOS.It has been shown that using DES as solvents allows reactions involving highly reactive organometallic reagents (e.g. Grignard or alkyllithium reagents) to take place even in the presence of water. This is very surprising, as these conditions would rapidly degrade the organometallic in conventional solvents. This project will take these observations further and develop novel catalytic reactions using DES as sustainable solvents under mild conditions, with no protection from atmospheric moisture or oxygen.