Contribution of the Centrifugal Partition Chromatography (CPC) to the Purification of Zincke Reaction Products

Abstract

The Zincke reaction poses a difficulty when attempting to purify the crude mixtures and isolate reaction products in analytically pure form. This paper introduces the successful method of using the centrifugal partition chromatography (CPC) to isolate pyridinium salts garnered by this reaction returning good yields and high degrees of purity. Efficient purifications were obtained by using (n‐BuOH/MeOH/H2O) biphasic solvent systems. The CPC confirmed its suitability for isolating compounds prone to decompose during purification on solid stationary phases. It has also proved to be an efficient method for valorizing incomplete Zincke reactions.

Glutaconaldehyde as an Alternative Reagent to the Zincke Salt for the Transformation of Primary Amines into Pyridinium Salts

“…All chemicals and solvents were purchased from commercial suppliers (glutaconaldehyde dianil hydrochloride 6 was purchased from TCI) and were used as received; H 2 O used as solvent was distillated. Zincke salt 4·Cl was prepared according to the reported procedure . MW-assisted reactions were carried out with an Anton Paar Monowave 300 reactor, provided with an IR temperature sensor.…”

“…Zincke salt 4•Cl was prepared according to the reported procedure. 21 MW-assisted reactions were carried out with an Anton Paar Monowave 300 reactor, provided with an IR temperature sensor. The automated purification of pyridinum salts was performed on a C18 reversed-phase instrument (40 g cartridges).…”

“…Despite its frequent use, the Zincke salt 4·Cl is associated with various limitations. Using this reagent in excess results in a mixture of salts 4·Cl and 2·Cl , inseparable according to traditional chromatographic methods . Consequently, weakly nucleophilic amines need to be engaged in large excess to fully convert the reagent.…”

“…Using this reagent in excess results in a mixture of salts 4•Cl and 2•Cl, inseparable according to traditional chromatographic methods. 21 Consequently, weakly nucleophilic amines need to be engaged in large excess to fully convert the reagent. Even so, reaction times may be long, especially under conventional activation.…”