A solution of 2-[2-methoxy-3-(2-chlorophenoxy)phenyl]butyric acid (4.1 g) in acetic anhydride (10 ml) and hydriodic acid (55-58%, 20 ml) were treated in a similar manner to that of Example 10-(7). The resultant oily residue, i.e. 2-[2-hydroxy-3-(2-chlorophenoxy)phenyl]butyric acid was treated with acetic anhydride (10 ml) in a similar manner to that of Example 10-(7). The resultant crystalline residue was recrystallized from ethanol to give 3-ethyl-7-(2-chlorophenoxy)-2,3-dihydrobenzofuran-2-one (2.3 g). mp 78°-79° C.
