For high-throughput synthesis and purification of ethanolamines, the method to retain selectively the basic products as ammonium sulfonate salts on strong cation-exchange sorbents was also used . An 8x6 reaction array employing eight different amines and six different epoxides was performed, and the products were obtained with an average yield of 75 % and an average purity of >92 %.
If neither the desired product nor the reagents and impurities are ionizable, the ion-exchange methods shown above are not convenient. Nevertheless, the selective isolation of the desired compound using ion-exchange adsorbents can be performed using a "phase-switch" approach . To achieve this, "phase-switch" quenching reagents were used to transform a neutral compound into an ionizable species that could be captured by an ion-exchange solid support. The principle is amenable to both anion- and cation-exchange chromatography, depending on the quenching agent employed. An illustration of the method is given in Scheme 12.
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