A process for the electrochemical direct C-H arylation of quinazolinones and aryl tetrafluoroborate diazonium salts with ionic liquid [EMIM]BF4 (1-ethyl-3-methylimidazolium tetrafluoroborate):H2O (2:1) as electrolyte was developed for the synthesis of 2-arylquinazolinones, and a series of 2-arylquinazolinones were synthesized with moderate to good yields. This method was applied for the synthesis of a key intermediate of an IKK β inhibitor CU160 and a quinazolinone alkaloid 2-(1H-indol-3-yl) quinazolin-4(3H)-one. The mild and green synthesis scheme provides an effective alternative to the traditional synthesis of 2-arylquinazolinone. © 2023 American Chemical Society