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
Conjugate addition of activated methylene derivatives to beta-nitro acrylic esters in acetonitrile with DBU (2 equiv) as base, allows the one pot formation of polyfunctionalized alpha,beta-unsaturated esters. The procedure is based on a tandem 'Michael addition elimination' process favoured by the Simultaneous behaviour of the nitro group as both an electron-withdrawing and leaving group. (C) 2005 Elsevier Ltd. All rights reserved.