Intermolecular Hydroamination

By: William Sommer, Aldrich ChemFiles 2009, 9.5, 3.

Aldrich ChemFiles 2009, 9.5, 3.

In 2003, Mizushima et al. reported the first intermolecular hydroamination of alkynes with primary amines.6 This new procedure, using gold as catalyst, allowed access to ketimides using relatively mild conditions. It is important to note that prior to this report, one of the most common procedures for the hydroamination of alkynes was through the aminomercuration of the alkynes followed by demercuration. The alternative to this procedure using gold catalysts is more environmentally friendly. For this reaction, Tanaka et al. use an acid promoter with PPh3AuCl. As low as 0.01 mol % of catalyst is needed for the reaction to occur with yields up to 99%. Various arylacetylenes substituted by electron-withdrawing and donating groups were reacted with numerous anilines resulting in excellent yields (Scheme 2). This first report of intermolecular hydroamination of alkynes using gold catalysts was the most efficient catalyst system.

Scheme 2.

In 2006, Dake and coworkers utilized this method to synthesize a variety of pyrroles (Scheme 3) to understand the role of silver salts and gold complexes.1 In this example, alkynes are reacted with an amine to produce the corresponding pyrrole using various gold catalysts. The authors concluded that silver or gold catalysts facilitate the reaction between amines and alkynes.

Scheme 3.

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  1. Harrison, T. J. et al. J. Org. Chem. 2006, 71, 4525.

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