Isatoic anhydride

Isatoic anhydride is an organic compound derived from anthranilic acid. A white solid, it is prepared by reaction of anthranilic acid with phosgene.

Reactions
Hydrolysis gives carbon dioxide and anthranilic acid. Alcoholysis proceeds similarly, affording the ester:
 * C6H4C2O3NH +  ROH  →   C6H4(CO2R)(NH2)  +  CO2

Amines also effect ring-opening. Active methylene compounds and carbanions replace oxygen giving hydroxyquinolinone derivatives. Deprotonation followed by alkylation gives the N-substituted derivatives. Sodium azide gives the benzimidazolone via the isocyanate. Isatoic anhydride is used as a blowing agent in the polymer industry, an application that exploits its tendency to release CO2.

Uses
Isatoic anhydride has been used as a precursor for the synthesis of methaqualone and related 4-quinazolinone-based pharmaceutical drugs, including:
 * 1) Tioperidone
 * 2) Tranilast
 * 3) Pelanserin
 * 4) Diproqualone
 * 5) Antrafenine
 * 6) SJ-733
 * 7) Nicafenine
 * 8) Molinazone
 * 9) Cloperidone
 * 10) SGB 1534