An efficient procedure for the synthesis of spiro [3H-indole-3,4′ (1 ′H) pyrano [2,3-C] pyrrole]-5′-carbonitriles using solid inorganic supports and microwave activation

Microwave irradiation accelerates the Michael condensation of 3-dicyanomethylene-2H-indole-2-one with 2-pyrrolidone/N-methyl-2-pyrrolidone (i) adsorbed on neutral alumina in "dry media" (ii) using absolute ethanol as energy transfer medium. 3-Dicyanomethylene-2H-indol-2-one was synthesized under microwave irradiation using indole-2,3-dione and malononitrile. The results were compared with those obtained following the classical method. The advantages obtained by the use of microwave irradiation are demonstrated.