Palladium-Catalyzed Cross-Coupling of Aryl Chlorides and Triflates with Sodium Cyanate: A Practical Synthesis of Unsymmetrical Ureas
Ekaterina V. Vinogradova, Brett P. Fors and Stephen L. Buchwald*
*Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States, Email: sbuchwalmit.edu
E. V. Vinogradova, B. P. Fors, S. L. Buchwald, J. Am. Chem. Soc., 2012, 134, 11132-11135.
DOI: 10.1021/ja305212v (free Supporting Information)
An efficient method for palladium-catalyzed cross-coupling of aryl chlorides and triflates with sodium cyanate allows the synthesis of unsymmetrical N,N′-di- and N,N,N′-trisubstituted ureas in one pot and is tolerant of a wide range of functional groups. Insight into the mechanism of aryl isocyanate formation was gleaned through studies of the transmetalation and reductive elimination steps of the reaction.
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Pd2dba3 and the ligand were preheated in toluene at 120°C for 3 minutes before the introduction to the reaction mixture.
Ekaterina Vinogradova, May 5, 2012