Synthesis of Benzazepines by Gold-Catalysed Reactions of N-Allenylamides

The gold-catalysed reactions of alleneamides give different products depending on the substrate and the reaction conditions. In particular, N-(2-alkynylphenyl)-N-allenyltosylamides give benzazepines when using gold(III) catalysts in the presence of nucleophiles. This sequential process may follow two different reaction pathways, and these are discussed. Metal coordination to the alkyne followed by nucleophilic attack of the allene and trapping of the intermediate with NuH accounts for the formation of 4, but coordination to the allene and addition of NuH to give 3, which can decompose into other products and also form 4, is postulated as a better explanation for these results. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)