Functionalization of five-membered heteroaromatics generally proceeds at the C2- and/or C5-position, whereas C3- and C4-positions are less reactive. The aim of our work was to selectively functionalize five-membered heterocycles with the use of two different transition metals (ruthenium and palladium) and quinoline as a directing group. We performed Ru-catalyzed C–H arylation of 2-heteroarylquinolines. Additionally, the formation of a five-membered ruthenacycle was proved, which was confirmed by crystal structure analysis of the complex. Further, Pd-catalyzed arylation of heterocycle was carried out. We studied the regioselectivity of the performed reactions and optimized the reaction conditions for each step of the reaction. We wanted to achieve the highest possible conversion to the final diarylated products. In both steps, the reactions of 2-heteroarylquinolines were carried out with different aryl bromides, which included both electron-withdrawing and electron-donating groups.
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