How is Apixaban Impurity 84 (CAS: 14273-86-0) typically synthesized?

Apixaban Impurity 84 (CAS: 14273-86-0) is synthesized through a multistep process involving condensation, oxidation, and purification steps. The synthesis typically uses organic solvents like dichloromethane and water. Catalysts such as sulfuric acid are employed for the initial steps, and the process yields about 85% purity. The final product is isolated via recrystallization and characterized by spectroscopic methods.