Annulation of 1-methylisoquinoline with pyrrolylacetylenic ketones: catalyst-free stereoselective synthesis of (E)-acylethenylpyrrolo[1',2':3,4]imidazo[2,1-a]isoquinolines

1-Methylisoquinoline undergoes stereoselective annulation with pyrrolylacetylenic ketones (MeCN, 80–82 °C) to provide (E)-acylethenylpyrrolo[1’,2’:3,4]imidazo[2,1-a]isoquinolines in up to 92% yield. In the case of 5-arylpyrrolylacetylenic ketones, instead of the above cyclization, the dimerization of the starting ketones to give dipyrrolopyrazines in 38 and 39% yields occurs.