Aromatic motifs are vital components of many approved drugs as well as drugs under clinical trial. Substituted benzene ring, which constitutes 63% of aromatic ring-containing small-molecule drugs, is the most prevalent ring system in pharmaceuticals (Fig. ). However, under physiological conditions, organic compounds with more than two substituted benzene rings often have poor solubility, low target specificity, and low metabolic stability thus halting the entry of pharmaceutical candidates to the final phases of drug development. Substituting benzene rings with heteroaromatic units (e.g., pyridine, pyrimidine, etc.) often proves to be crucial in fine-tuning such molecular functions. As a result, heteroaromatic units are being increasingly incorporated in pharmaceutical candidates.