Reactions of diazoalkanes with isocyanates. Synthesis of imidazolidine-2,4-diones, oxindoles, and oxazolidinones

Thermolysis of a 5,5-dialkyl-Δ 3 -1,3,4-oxadiazolin-2-one in nitrobenzene containing an aryl isocyanate at 150° C affords a 1,3-diaryl-5,5-dialkylimidazolidine-2,4-dione, an N-arylcarbamoyl-3,3-dialkyloxindole, and a 3-aryl-2-arylimino-5,5-dialkyl-1,3-oxazolidin-4-one. Those products arise from attack of a diazoalkane, generated insitu from the oxadiazolinone by thermal cycloreversion, on the isocyanate function. Two imidazolidine diones, three oxazolidinones, and 14 oxindoles were prepared.