How is 2',4',5',7'-Tetrabromo-4,5,6,7-tetrachloro-3',6'-dihydroxy-3H-spiro[2-benzofuran-1,9'-xanthen]-3-one (CAS: 13473-26-2) typically synthesized?

2',4',5',7'-Tetrabromo-4,5,6,7-tetrachloro-3',6'-dihydroxy-3H-spiro[2-benzofuran-1,9'-xanthen]-3-one is synthesized through a multi-step process involving bromination, chlorination, and hydroxylation reactions. Commonly, the synthesis involves starting materials such as xanthenone, which undergoes bromination and chlorination reactions sequentially, followed by hydroxylation. The reaction conditions include the use of Lewis acids and strong bases, and the process is optimized for high yield and selectivity.