2-Aminothiophene derivatives in a novel synthesis of phthalimidines

New aminophthalides were synthesized from o -formylbenzoic acid and substituted 2-aminothiophenes. Two of these compounds underwent recyclization in boiling Ac 2 O to give the previously unknown 3-acetoxy-2-(3-cyano-4,5-dimethylthiophen-2-yl)-1,3-dihydroisoindol-1-one and 3-acetoxy-2-(3-cyano-4,5-tetramethylenethiophen-2-yl)-1,3-dihydroisoindol-1-one. The possible reaction mechanism and factors preventing the recyclization, in particular, the formation of intramolecular hydrogen bonds in the starting phthalides, were discussed. Some reactions of the resulting compounds with C-nucleophiles in trifluoroacetic acid were investigated. Two derivatives containing 4-hydroxy-3,5-di- tert -butylphenyl substituents were studied by X-ray diffraction.