Formation of 3,4-dihydro-α-carbolines from 2-aminoindole

In the condensation of 2-aminoindole with ,-unsaturated oxo compounds, in contrast to ordinary aromatic amines and a number of heterocyclic amines, the direction of cyclization is reversed. The general scheme of the reaction includes the reaction of the position of 2-aminoindole with the activated double bond of the oxo compound via a mechanism of the Michael type and condensation of the carbonyl group of the unsaturated carboline structure, which subsequently undergoes aromatization. The intermediate 3,4-dihydro--carbolines were produced and isolated; this made it possible in a number of cases to establish the structures of the final -carbolines. The structures of the 3,4-dihydro compounds were confirmed by the set of spectral characteristics. Data from the UV, IR, PMR, and mass spectra are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 945–951, pp. 945–951, July, 1977.