On the other hand, Zhao et al. and Yu et al. reported a direct C-H arylation using N-phthaloyl-L-alanine (19) without aminoquinoline in 2017. This reaction does not require aminoquinoline and is highly efficient and atom-economic, as it eliminates the need for aminoquinoline removal after C-H activation. Following Zhao's conditions, C-H biarylation was attempted using carboxylic acid 19 and aryl iodide 18. Investigation of various conditions revealed that Ac-Gly-OH, as an amino acid ligand, effectively promoted concerted metallation deprotonation (CMD) and provided the desired compound 22 with an isolated yield of 71%. The reaction mechanism is proposed as follows: the carboxylate of N-phthaloyl-L-alanine ( ), generated by Ac-Gly-OH and K2CO3, coordinates to Pd(II) to form intermediate 20 in the reaction system. This intermediate 20 is efficiently promoted by the acetyl group of Ac-Gly-OH, facilitating CMD and C-H metalation. Subsequently, oxidative addition of aryl iodide 18 leads to the formation of intermediate 21. Finally, reductive elimination results in the conversion of intermediate 21 into the desired product 22. It is worth mentioning that when Boc-Gly-OH was used as a ligand, only trace amounts of the desired compound 22 were obtained. These experimental results clearly indicate the essential role of the acetyl group in this reaction. Further optimization of this C-H biarylation is described in Figure .