The general objectives of this project revolved around the recent research field of C-H bond functionalization. Research in this field aims to demonstrate and improve the modification of organic molecules via the activation and subsequent functionalization of C-H bonds, very common in most organic molecules. The abundance of such bonds make them a versatile handle to increase the complexity of organic compounds; moreover, as such modifications do not require pre-functionalized starting materials, they have the advantage, compared to other methods, to considerably reduce the waste generated during the chemical reaction. The reduction of chemical waste has obvious advantages for society, environment, and industry.
As C-H bonds are relatively unreactive, specific conditions need to be applied for the process to occur in an effective manner, such as transition metal catalysis, photochemistry, and use of oxidants.
Continuous flow chemistry is an alternative methods to perform chemical reactions. In comparison to the classical mixing-and-stirring method typically used, flow chemistry involves pushing the reactants and reagents into a (micro)channel, where the reaction conditions (temperature, pressure, etc) are applied. The advantages of this methods are multiple, including: better heat transfer, better mixing, better irradiation (for photochemical processes), higher safety, and the possibility to continuously monitor the process. In many cases, this results in faster and safer reactions, and better yields and selectivity. Furthermore, it is a continuous method, which makes it suitable for large scale processes.
Due to the low reactivity of C-H bonds, and the often low selectivity of their functionalization (due to the many C-H bonds present in a typical molecule), flow chemistry offer the potential to improve the efficiency and applicability of these transformations. The objectives of this project were to demonstrate the efficiency and applicability of continuous flow chemistry techniques to this field.
The work undertaken during the action demonstrates that indeed flow chemistry can be effective to improve the outcome of C-H functionalization reactions, with particular effects in reducing the reaction time required, and/or increase the productivity in a continuous process. Good part of this work for carried out for light promoted transformations, which offer even more waste-reducing alternatives than metal-catalysed reactions, and for which flow chemistry shows even better performances.
