TBD-catalysed solventless synthesis of symmetrically N,N′-substituted ureas from primary amines and diethyl carbonate

Symmetrically N,N′-substituted ureas were obtained from primary amines in very good yields under solvent-less conditions using diethyl carbonate (DEC) as the carbonylation reagent and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as the base catalyst. The products are precipitated directly from the reaction mixture after a volatile organic compound (VOC) free aqueous work-up. The catalyst can be recovered and reused.