Asymmetric Organocatalytic Reactions under Ball Milling
In recent decades, the development of a large number of chemical processes has been carried out following the principles of “green chemistry”, which among other goals seeks to minimize the use of volatile and potentially toxic solvents. Not too long ago, the thought of carrying out chemical processes in the absence of solvent was considered impossible. However, nowadays there exist several mechanical activation techniques such as high-speed ball milling (HSBM) that may enhance substantially the efficiency of a chemical synthesis under more sustainable reaction conditions. In particular, the HSBM technique is a powerful tool to carry out solvent-free organic reactions with concomitant optimization of the use of energy. Indeed, HSBM activation may well be the “greenest” mechanical activation technique. In this chapter, we will review the use of the HSBM technique in asymmetric organocatalytic reactions under solvent-free conditions.