Molecular Design of Organic Superbases, Azacalix[3](2,6)pyridines: Catalysts for 1,2- and 1,4-Additions

The molecular design, characteristics, and catalytic
activity of
macrocyclic amino compounds, azacalix[3]­(2,6)­pyridine derivatives,
were studied. The introduction of an electron-donating group on the
pyridine moiety and bridging amino phenyl group enabled the enhancement
of the basicity of azacalix[3]­(2,6)­pyridine up to pKBH+ = 29.5 in CD3CN. These derivatives
were shown to be efficient catalysts for 1,4-addition reactions of
nitroalkanes or primary alcohols to α,β-unsaturated carbonyl
compounds and 1,2-addition reactions of nitroalkanes to aromatic aldehydes.