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Highly Enantioselective Hydrogenation of Unsaturated Ureas
C. A. Busacca*, J. C. Lorenz, N. Grinberg, N. Haddad, H. Lee, Z. Li, M. Liang, D. Reeves, A. Saha, R. Varsolona, C. H. Senanayake
Boehringer-Ingelheim Pharmaceuticals Inc., Ridgefield, USA
19 March 2008 (online)
A family of P,N ligands is reported to achieve the hydrogenation of unsaturated urea esters with levels of enantioselection previously only attainable with P,P ligands. In contrast to unsaturated amino esters, the direct enantioselective hydrogenation of unsaturated ureas is not well investigated. The new catalytic hydrogenation system proved to tolerate a wide range of functional groups, including the hindered terminal alkene 4.