Synthesis of 1,2‐oxazaheterocycles containing an isoindolone moiety from N‐Hydroxyphthalimide

Syntheses of the isoindolobenzoxazinone 1a and thienoxazinoisoindolones 1b,c was developed from N-hydroxyphthalimide 3 and halogenomethylaryl derivatives. The resulting aryloxy phthalimides 4a-c were reduced to hydroxylactams 5a-c which cyclized in acidic conditions. A Wittig reaction on 5a using carbethoxymethylidenetriphenylphosphorane gave the corresponding acid 6 which treated in Friedel and Crafts conditions led to the isoxazolinone 8 by cleavage of the benzyl CO bond.