Issue Date: June 11, 2007
Silver mediates C–H aminations
Nitrogen-containing functional groups abound in natural products and pharmaceutical chemistry, which is why methods to directly transform C–H bonds into C–N functional groups are so useful. Chuan He and colleagues at the University of Chicago now report a new pathway for such conversions: the first intermolecular amination of saturated C-H bonds facilitated by a silver-based catalyst (Angew. Chem. Int. Ed., DOI: 10.1002/anie.200700760). Although other metal catalysts can perform this trick, the new catalyst is more reactive and cost-efficient, the researchers note. The team prepared the catalyst by combining silver(I) trifluoromethanesulfonate with 4,7-diphenyl-1,10-phenanthroline ligands. With an iminoiodane (C6H5I=NR, R = p-nitrosulfonyl) as the nitrogen source, the catalyst activates benzylic C–H bonds to form amines in moderate yields (one shown) and converts otherwise inert cycloalkanes to amines in low yields. What makes this catalyst productive when other silver-based versions have failed? The researchers' preliminary mechanistic studies show that it's the catalyst's unusual disilver(I) core with the phenanthrolines stacked one above the other.
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