N-(1,3-Dihydro-1,3-dioxo-5-isobenzofuranyl)acetamide; 4-(Acetylamino)phthalic anhydride;Apremilast Impurity 47;N-(1,3-Dioxo-1,3-dihydroisobenzofuran-5-yl)acetamide;4-acetamido-Phthalic anhydride