Achievement of regioselectivity in transition metal-catalyzed direct C–H (hetero)arylation reactions of heteroarenes with one heteroatom through the use of removable protecting/blocking substituents or traceless directing groups

This review with 453 references covers the literature up to the end of April 2015 on the transition metal-catalyzed direct C-H (hetero)arylation reactions of heteroarenes with one heteroatom in which high regioselectivity has been gained by the use of removable protecting/blocking substituents or traceless directing groups. Particular attention has been devoted to illustrate the typical features of these methods, and to summarize the synthetic procedures used for the introduction of removable protecting/blocking groups in the heteroarene substrates and their subsequent removal from the reaction products. The limitations related to the use of protecting/blocking substituents and directing groups, such as an increase in synthetic steps or the fact that, in many cases, the (hetero)arylation reactions assisted by directing groups involve only C-H bonds ortho to the directing group, will also be highlighted.