Reaction of aldehydes with an excess of nitromethane in the presence of basic alumina as solid catalyst allows the one pot preparation of 1,3-dinitroalkanes. The synthesis proceeds through the nitroaldol reaction of nitromethane, which acts both as nucleophile and as solvent, to the aldehydes with the formation of β-nitroalkanols as intermediates that convert to nitroalkenes. Further nucleophilic behavior of the nitromethane produces the in situ conjugate addition of its carbanion to the formed nitroalkenes giving the one-pot synthesis of the title compounds. The catalyst shows general applicability with aliphatic, aromatic and heteroaromatic aldehydes.
1,3-dinitroalkanes - Michael additions - heterogeneous catalysis - alumina - one-pot
