Silver-catalysed intramolecular cyclisation of 2-alkynylacetophenones and 3-acetyl-2-alkynylpyridines in the presence of ammonia

Silver catalysed/microwave assisted domino reactions of 2-alkynyl-acetophenones and 3-acetyl-2-alkynylpyridines in the presence of ammonia are widely described. In most cases the reaction give a mixture of the imino- and carbo-cyclisation products, with a general preference for the former. A plausible mechanism is proposed and the dual activity of silver salts is supported by NMR experiments.