The synthesis of a family of O-silylcarbamates from the corresponding silylamines has been achieved simply by heating the silylamine in supercritical carbon dioxide (scCO2), and these O-silylcarbamates have been shown to be effective precursors for the synthesis of a range of symmetrical and unsymmetrical ureas.

Palladium catalysed C-N bond formation in supercritical carbon dioxide has been accomplished. Carbamic acid formation is avoided in part through the use of an N-silylamine as the coupling partner. Employing a catalyst system of Pd2dba3(1 mol%) and 2-dicyclohexylphosphino-2',4',6'-triisopropyl-1,1'-biphenyl (X-Phos)(2 mol%) enabled the catalytic amination of aryl bromides and chlorides with N-silylanilines to be realised in excellent yield. Extension of the methodology to the N-arylation of N-silyldiarylamines, N-silylazoles and N-silylsulfonamides is reported.

Amines Q 0120Palladium-Catalyzed Aryl Amination Reactions in Supercritical Carbon Dioxide.-The investigation is carried out with a view to the processing and environmental benefits of supercritical CO2 as the solvent. -(SMITH*, C. J.; TSANG, M. W. S.; HOLMES, A. B.; DANHEISER, R. L.; TESTER, J. W.; Org. Biomol. Chem. 3 (2005) 20, 3767-3781; Dep. Chem., Univ. Cambridge, Cambridge CB2 1EW, UK; Eng.) -Nuesgen 09-077