Issue Date: October 1, 2012
Biaryls Spun From Gold
When chemists want to link two aryl groups, they usually turn to cross-coupling methods that marry aryl halides with aryl metallics. Chemists at the University of Bristol, in England, now offer an alternative: a direct arylation that joins arenes to aryl silanes in a site-selective manner (Science, DOI: 10.1126/science.1225709). Developed by Liam T. Ball, Guy C. Lloyd-Jones, and Christopher A. Russell, the reaction uses a gold catalyst and a mild oxidant formed in situ from iodobenzene diacetate and camphorsulfonic acid. The arylation site is predictable on the basis of electrophilic aromatic substitution pathways. The reaction proceeds at room temperature and works in the presence of functional groups such as reactive halogens, which normally can’t be carried through cross-coupling reactions and used in subsequent reactions. Using robust aryl silanes as substrates, rather than aryl metallics, offers a couple of advantages, the researchers say. The silane can be installed early in the synthesis, and it’s not as air sensitive or toxic as conventional aryl metallics can be. To demonstrate the reaction’s utility, the Bristol team used it to make the nonsteroidal anti-inflammatory compound diflunisal.
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