Acetate assisted C-H activation: A computational and experimental study

从制药到塑料，各种各样的复杂有机分子在广泛的日常应用中都很重要。一般来说，这些分子的合成是由比较简单的起始材料完成的。这种起始材料的一个关键特征是具有反应性官能团。通常这是一个卤化基团，比如C-Cl键。然而，这种官能团的形成往往效率低下，并产生对环境有害的废物-在这种情况下是氯化废物。原则上，理想的官能团应该是碳氢键。含有碳氢键的起始材料丰富且极其便宜，因此不需要任何浪费的事先操作。不幸的是，碳氢键有一个巨大的缺点——它们通常极不活泼。然而，我们已经发现了一种方法，通过使用特定的金属配合物与特定的碱，醋酸盐结合，来增强C-H键的反应性。初步研究表明，带正电的金属可以攻击C-H键，使其容易被醋酸酯裂解。这个过程的结果是通过生成新的金属-碳键来“激活”碳氢键。金属-碳键一旦形成，就具有很强的反应性，并经历广泛的选择性转化，包括形成C-C键，这将允许合成更复杂的有机分子。基于我们的新金属促进的碳氢键活化加上碳碳键形成的催化过程将非常有吸引力，因为它既高效（避免了其他活性官能团的浪费形成）又环保（避免了副产物的形成）。在我们提出的工作中，我们的目标是了解我们观察到的C-H键容易激活背后的基本化学。我们将使用计算模型和实验化学来精确地研究促进这一过程的因素。一旦确定了这些因素，就可以包括在C-H活化的新催化剂的设计中。

A huge variety of complex organic molecules are important in a wide range of everyday applications - from pharmaceuticals to plastics. In general the synthesis of these molecules is achieved from somewhat simpler starting materials. A key feature of such startng materials is the presence of a reactive functional group. Often this will be a halogenated group, such as a C-Cl bond. However, the formation of such functional groups is often inefficient and generates environmentally damaging waste - in this case chlorinated waste.In principle, an ideal functional group would be a C-H bond. Starting materials containing C-H bonds are abundant and extremely cheap and so do not require any wasteful prior manipulation. Unfortunately, C-H bonds have one huge drawback - they are generally extremely unreactive. However, we have discovered a way to enhance the reactivity of C-H bonds by using certain metal complexes in combination with a particular base, acetate. Preliminary studies suggest that a positively charged metal can attack a C-H bond and make it susceptible to cleavage by acetate. The result of this process is to 'activate' the C-H bond by making a new metal-carbon bond. Once formed, metal-carbon bonds are very reactive and undergo a wide range of selective transformations, including the formation of C-C bonds that will allow the synthesis of more complicated organic molecules. A catalytic process based on our new metal-promoted C-H activation coupled followed by C-C bond formation would be extremely attractive as it is both extremely efficient (avoids wasteful formation of other reactive functional groups) and environmentally friendly (avoids the formation of byproducts). In our proposed work we aim to understand the fundamental chemistry that lies behind our observation of easy C-H bond activation. We shall use both computational modelling and experimental chemistry to investigate precisely what factors promote this process. Once identified these factors can be included in the design of new catalysts for C-H activation.