Convenient synthesis of (Z)-3-(1-aryl-2-nitrovinyl)-indoles

3-(1-Aryl-2-nitrovinyl)-indoles were previously described in the literature only once as side products of an unrelated process as mixtures of Z- and E-isomers. Herein, we discovered a new process toward their synthesis where substituted indoles are combined with 2-nitroacetophenones in acetic acid in the presence of 10 mol% H2SO4 to give 70–90% yields of such compounds possessing exclusively or predominantly Z-geometry. The latter was established through NOESY and x-ray studies of individual products.