Synthesis and recovery of pyridine- and piperidine-based camphorsulfonamide organocatalysts used for Michael addition reaction
Two new pyridine-based asymmetric bifunctional organocatalysts containing one or two camphorsulfonamide units were synthesized. Asymmetric Michael addition of pentane-2,4-dione to β-nitrostyrene was catalyzed by these organocatalysts. During our experiments, influence of the solvent and temperature on the yield and enantioselectivity was studied. Using monocamphorsulfonamide derivative the S enantiomer of the corresponding Michael adduct was gained with moderate yield (up to 51 %) and low enantiomeric excess (up to 18 %). Organic solvent nanofiltration was successfully applied for the recovery of these organocatalysts. Furthermore, pyridine camphorsulfonamide was reduced to its piperidine derivative. Using piperidine monosulfonamide derivative racemic Michael adduct was obtained with excellent yield (up to 89 %). Beside its organocatalytic relevance, piperidine monosulfonamide derivative may also possess biological activity.