alumina is found to promote the conjugate addition of indoles to nitroalkenes in solventlessconditions at 60 °C. Nitroalkenes can be replaced by nitro alcohols that are converted into nitroolefins under the reaction conditions. Alternatively, a tandem nitroaldol-dehydration allows the utilization of nitroalkanes and aldehydes as remote precursors of reactive nitroalkenes in a ‘one–pot’ synthesis of 3-substituted
Improved preparation of alkyl 2-(3-indolyl)-3-nitroalkanoates under fully heterogeneous conditions: stereoselective synthesis of alkyl (E)-2-(3-indolyl)-2-alkenoates
the presence of basic alumina affords ethyl 2-(3-indolyl)-3-nitroalkanoates that are central intermediates for the preparation of tryptamines and carboline alkaloids. A base promoted elimination of nitrous acid from these nitroindolyl derivatives readily produces ethyl 2-(3-indolyl)-2-alkenoates with high E stereoselectivity. The latter compounds can be used as Michael acceptors in intra- and intermolecular