Green and Practical Synthesis of Carbamates from Ureas and Organic Carbonates

Abstract

A practical method for the synthesis of carbamates from ureas and organic carbonates was developed with 100% atom economy using La₂O₃/SiO₂ as catalyst without any additional solvent. The scope of the protocol is demonstrated in the synthesis of 14 carbamates with various functional groups in excellent yields (76–95%).

Keywords:

• Atom economy
• carbamates
• carbonates
• clean synthesis
• lanthana
• urea derivatives

ACKNOWLEDGMENTS

This work has been financially supported by the National Natural Science Foundation of China (No. 20503037). We thank Bayer Material Science for financial support.

Notes

^a 5 mmol (1.12 g) DCU, 50 mg (0.3 mol La%) La₂O₃/SiO₂.

^b Conversion of DCU determined by GC-FID.

^c Chemoselectivity to MCC determined by GC-FID.

^d Isolated yield.

^e Commercial SiO₂ (200–300 mesh, BET surface area = 601.1 m²/g, pore volume = 0.74 cm³/g, average pore diameter = 4.93 nm). It was pretreated at 600 °C for 4 h and then cooled in a dryer before use.

^f The 12th run of a recovered catalyst.

^a 5 mmol disubstituted ureas, 75 mmol carbonates, 50 mg (0.3 mol La%) La₂O₃/SiO₂, 150 °C.

^b Isolated yield.

^c 120 °C.