Lipase-catalyzed acetylations of 1-phenylethanol with vinyl acetate were monitored in situ by 1H NMR spectroscopy. Surprisingly, even under dry conditions (no added water) the major reaction was hydrolysis of the vinyl acetate, not acetylation of the substrate. Because this competing hydrolysis consumes water and releases acetic acid, the reaction conditions in lipase-catalyzed acylations are not constant, but vary with the reaction time. Addition of a chiral shift reagent reveals the enantiomeric purity of the starting alcohol and allows calculation of the enantiomeric ratio, E, for the reaction.
Bibliographical noteFunding Information:
We thank Dr. Françoise Sauriol (McGill University) for perfect technical support. H. K. Weber thanks the Austrian Science Foundation (FWF) for an Erwin-Schrödinger-Auslandsstipendium as a postdoctoral fellow at McGill University.
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