The given compound is an acid anhydride. Acid anhydrides are named as (acid)1(acid)2−anhydride where (acid)1 and (acid)2 are the acidic parts where carbonyl carbon is also counted. In the given compound, (acid)1 is benzoic acid while (acid)2 is propanoic acid. Hence its IUPAC name is benzoic propanoic anhydride.