In situ slow release of isocyanates: synthesis and organocatalytic application of N-acylureas

A novel, efficient, and operationally simple one-pot synthesis of both, symmetrical and unsymmetrical N-acylureas from carboxamides and in situ generated isocyanates (from N,N-dibromo-p-toluenesulfonamide) in the presence of a mild base at rt is reported. The protocol avoids the tedious isolation and purification steps of hazardous isocyanates. The first application of these acylureas to the catalysis through hydrogen bonding is also demonstrated.