Anthranilic acid is prepared by the Hoffman rearrangement of thalamide with sodium hypochlorite bleach. The procedure forms sodium thalamide from thalamide and sodium hydroxide at cold temperature, then reacts with chilled sodium hypochlorite to generate an isocyanate intermediate that rearranges to sodium anthranilate on heating. After neutralization, the solution is acidified with glacial acetic acid to precipitate anthranilic acid, which is then filtered and dried. The crude product yield is about 12.4 g from 30 g starting material (roughly 44%), with higher yields reported in other variants (up to ~60%). Recrystallization from boiling water (water >95 C) can improve purity. Anthranilic acid is a versatile starting point for benzene derivatives, dyes, and quinazolinone heterocycles.
