Synthesis, Characterization, and Catalytic Reactivity of a Highly Basic Macrotricyclic Aminopyridine

The synthesis methods, physicochemical and structural characteristics, and catalytic reactivity of new macrocyclic proton chelators, N,N ',N ''-tris(p-tolyl)azacalix[3](2,6)(4-pyrrolidinopyridine) and N,N ',N ''-tris(p-tolyl)azacalix[3](2,6)(4-piperidinopyridine), are studied. The introduction of pyrrolidino and piperidino groups into the pyridine unit enables the enhancement of the synergistic proton affinity of the cavity of the macrotricycle giving a high basicity (pK(BH+) = 28.1 and 27.1 in CD3CN), resulting in a catalytic activity for the Michael addition of nitromethane with alpha,beta-unsaturated carbonyl compounds.