The silylation of butane-2,3-dione(I) with TMSCl and TEA in hot DMF gives the silylated enol (II), which is cyclized with dimethyl acetylenedicarboxylate (III) in refluxing toluene to yield 4,5-bis(trimethylsilyloxy)-3,6-dihydrophthalic acid dimethyl ester (IV). The condensation of (IV) with aniline (V), with simultaneous aromatization in refluxing acetic acid affords 4,5-bis(phenylamino)phthalic acid dimethyl ester (VI), which is hydrolyzed with LiOH in methanol and anhydrized with acetic anhydride in toluene giving the corresponding phthalic anhydride (VII). Finally this compound is treated with ammonium formate at 140-50 C to furnish the target phthalimide.

The silylation of butane-2,3-dione(I) with TMSCl and TEA in hot DMF gives the silylated enol (II), which is cyclized with dimethyl acetylenedicarboxylate (III) in refluxing toluene to yield 4,5-bis(trimethylsilyloxy)-3,6-dihydrophthalic acid dimethyl ester (IV). The condensation of (IV) with 4-fluoroaniline (V), with simultaneous aromatization in refluxing acetic acid affords 4,5-bis(4-fluorophenylamino)phthalic acid dimethyl ester (VI), which is hydrolyzed with LiOH in methanol and anhydrized with acetic anhydride in toluene giving the corresponding phthalic anhydride (VII). Finally this compound is treated with ammonium formate at 140-50 C to furnish the target phthalimide.