Arene C–H functionalisation using a removable/modifiable or a traceless directing group strategy
The use of coordinating moieties as directing groups for the functionalisation of aromatic carbon–hydrogen (C–H) bonds has become an efficient strategy for the selective construction of new carbon–carbon (C–C) and carbon–heteroatom (C–X) bonds in arenes. However many directing groups cannot be easily removed/modified from the products after C–H functionalisation, thus limiting the structural diversity of the products. This limitation can be overcome by employing removable/modifiable or traceless directing groups which can be easily attached to the starting materials and detached from the products. In this tutorial review, we give an overview of recent advances in this emerging field which have dramatically increased the synthetic applicability of C–H functionalisation processes.