Synthesis of 2H-Isoindole-4,7-diones by 1,3-Dipolar Addition of Oxazolium 5-Oxides to 1,4-Quinones

Article abstract of DOI:10.1021/jo01295a006

A general, convenient synthesis of 2H-isoindole-4,7-diones from readily available starting materials is described. 3-Methyl-2,4-diphenyloxazolium 5-oxide, formed by dehydrative cyclization of N-methyl-N-benzoyl-C-phenylglycine, combines with 1,4-quinones to produce 2H-isoindole-4,7-diones in moderate yields.Conversion of other N-acyl amino acids to the corresponding less stable oxazolium 5-oxides in solution using 1 equiv of acetic anhydride or dicyclohexylcarbodiimide and subsequent reaction with 1,4-quinones also affords 2H-isoindole-4,7-diones.