Uses
Caronic anhydride, also known as 6,6-Dimethyl-3-oxabicyclo[3.1.0]hexane-2,4-dione, is a pharmaceutical intermediate mainly used as a synthesis of Boceprevir, an oral protease inhibitor of hepatitis C. It is widely used in agricultural chemicals and other organic synthesis field.
Synthesis
Step 1: Ethyl dichlorochrysanthemate in ethyl acetate is ozonized at -5C until conversion exceeds 99%. Work-up, saponification, acidification, extraction, and concentration yield 3,3-dimethyl-1,2-cyclopropanedicarboxylic acid.
Step 2: The diacid is heated with acetic anhydride and sodium acetate at 170C to form the anhydride via dehydration. Work-up and recrystallization from toluene/petroleum ether give 6,6-dimethyl-3-oxabicyclo[3.1.0]hexane-2,4-dione (Caronic anhydride).
