Introduction of the pyrazolidine ring into the pyrrole ring of indole

The reaction of indoles with 1-acyl-5-hydroxypyrazolidines under heterogeneous catalysis conditions leads, depending on the structure of indole, to 2- and/or 3-(1-acyl-5-pyrazolidinyl)indoles. Thus, the formation of 2-pyrazolidinylindoles is the results of an unco-substitution at the 3-position of the indole, followed by migration of the pyrazolidine ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1207–1213, September, 1990.