Transition metal catalyzed borylation reactions have an important place in organometallic chemistry. In recent years, these reactions have been extensively investigated and have become a versatile tool in the synthesis of new organic materials. C-H bonds can be easily transformed into C-B bonds by borylation reactions. In particular, iridium-catalyzed borylation includes significant advances such as mild reaction conditions, additive-free, high efficiency and being in a single step. In this thesis, the borylation of dihydroisoquinolines with a wide range of biological properties was performed for the first time. Investigating the extent of the reaction has led to the development of optimization studies. Besides, the effects of steric and electronic factors on selectivity are also shown. In this new methodology, C3-borylated products with high regioselectivity and yield were formed with the directing effect of the acyl group. The use of AsPh3 as a ligand is critical to the product selectivity of the method. When the reagent scope was investigated, it was determined that the functional group tolerance of the reactions was quite high. Finally, borylated dihydroisoquinolines have been converted into various intermediates by application studies.