The importance of aryl isocyanates in organic synthesis stems from the possibility to easily transform these molecules into carbamates and ureas � functional groups that are present in a number of biologically active compounds (pharmaceuticals, agrochemicals) and polymeric materials (polyurethanes). Unfortunately, existing methods for the synthesis of aryl isocyanates have a number of limitations, such as narrow substrate scope, low yields, harsh conditions and the use of toxic reagents. To address these shortcomings, a new method for the synthesis of aryl isocyanates from aryl halides and triflates via palladium catalyzed cross-coupling with sodium cyanate was recently developed by our group.1The scope of this method is broad and includes substrates possessing a number of common functional groups as well as a variety of heterocyclic substrates. The method allows for the efficient one-pot synthesis of unsymmetrical N,N'-di- and N,N,N'-trisubstituted ureas, aryl S-thiocarbamates and aryl carbamates, including a number of important carbamate protecting groups.Mechanistic insights for this transformation were obtained through a series of competition experiments with different ArX (X = I, Br, Cl) substrates as well as stoichiometric studies of the elementary steps within the proposed catalytic cycle. These studies revealed the first example of reductive elimination from the complex bearing an aryl and an isocyanate groups to efficiently form an aryl isocyanate species. 1. Vinogradova, E. V.; Fors, B. P.; Buchwald S. L. J. Am. Chem. Soc. 2012  ,134, 11132.

Palladium-catalyzed cross-coupling of aryl chlorides and triflates with sodium cyanate: A practical synthesis of unsymmetrical ureas, aryl carbamates and S-thiocarbamates

245th National Meeting (2013)

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