Facile clay-induced Fischer indole synthesis: A new approach to synthesis of 1,2,3,4-tetrahydrocarbazole and indoles

Preparation of 1,2,3,4-tetrahydrocarbazole and substituted indoles, using a solid acid catalyst (namely K-10 montmorillonite clay) via Fischer indole synthesis in methanol medium, is described. The results obtained by the thermal method are compared with those from microwave irradiation. Active participation by adjacent acidic and basic sites of clays is proposed.