Isocyanurate Formation During Oxazolidinone Synthesis from Epoxides and Isocyanates Catalysed by a Chromium(Salphen) Complex

Chromium(salphen) complex 10 is found to be a catalyst for the preparation of oxazolidinones from epoxides and isocyanates. Using the optimal reaction conditions (1.5 mol % of chromium(salphen) complex 10 at 80 °C in toluene for 4 hours), six epoxides were reacted with five isocyanates, providing 15 oxazolidinones in up to 90 % yield. With electron-deficient isocyanates, cyclotrimerisation of the isocyanate to the corresponding isocyanurates is a competing reaction, showing the importance of matching catalyst activity to that of the substrates.