Issue Date: December 19, 2011
Palladium-catalyzed cross-couplings have become one of the most indispensable types of reactions in organic synthesis—they were the basis of the 2010 Nobel Prize in Chemistry. Chemists are still coming up with new applications for the method. In the latest example, Ryan M. Stolley, Wenxing Guo, and Janis Louie of the University of Utah report the first cross-couplings involving cyanamides (Org. Lett., DOI: 10.1021/ol203069p). Cyanamides are versatile N–C–N building blocks used to make guanidine-containing molecules, amidines, and a variety of heterocycles. These compounds find uses as antiviral and anticancer drugs, as well as organometallic ligands. Current methods to make cyanamides are sparse and tend to provide low yields, the researchers note. Louie’s team first screened precatalyst-ligand combinations and found that a palladium dibenzylideneacetone complex with the biphenyl phosphine ligand tert-butyl XPhos worked best. The Utah chemists then explored cyanamide cross-couplings with a range of aryl, heteroaryl, and vinyl partners. The reactions proceeded selectively under mild conditions within three hours in moderate to high yields, they report.
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