Convenient modification of the Leimgruber-Batcho indole synthesis: reduction of 2-nitro-β-pyrrolidinostyrenes by the FeCl3–activated carbon–N2H4∙H2O system
A new catalytic system containing ferric chloride, activated carbon, and hydrazine has been proposed for the reductive cyclization of β-dialkylamino-2-nitrostyrenes to give the corresponding indoles (Leimgruber-Batcho synthesis). Various substituted indoles may be obtained in high yield under these conditions.