Synthesis of N-(indol-3-yl)-N′,N′-dialkylamidines by the vilsmeier reaction with 3-aminoindoles

3-Aminoindoles substituted at C-2 and C-5 of the indole ring are converted by the action of Vilsmeier complexes into N-(indol-3-yl)-N,N-dialkylamidines. When C-2 is unsubstituted, the formylation proceeds but not the acetylation of this position. N-(Indol-3-yl)-N,N-dimethylacetamidine reacts with the complex obtained from DMF and POCl₃ to give 2-dimethylamino-3-formyl--carboline. The optimal conditions were found for the conversion of amidines to amides.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 76–81, January, 1985.