How is Avatrombopag Impurity 8 (CAS: 570407-42-0) typically synthesized?

Avatrombopag Impurity 8 is synthesized through a multi-step process involving Friedel-Crafts alkylation and subsequent ring-opening reactions. Common catalysts include Lewis acids such as aluminum chloride. The synthetic route produces a high yield of the desired impurity with good selectivity. However, the process requires careful control of reaction conditions to avoid formation of undesired by-products.