Abstract
This paper reports an easy characterization of carboxylic-trifluoroacetic mixed anhydrides by 1 H and 13 C NMR, and gives evidence that mixed anhydrides are produced instantaneously, at room temperature, from a carboxylic acid and trifluoroacetic anhydride and even from carboxylic anhydrides and trifluoroacetic acid. The esterification of phenol with the carboxylic- trifluoroacetic anhydrides is highly chemoselective, and affords pure products, in quantitative yields, and in the case of cholesterol, some cholesteryl trifluoroacetate is also produced.
Highlights
Esterification is a common procedure, widely reviewed,[1] to transform carboxylic acids or their derivatives into an ester functional group, to protect alcohols or to achieve molecular features
The common procedure to prepare mixed carboxylic-trifluoroacetic anhydrides is to heat a mixture of several equivalents of the carboxylic acid and trifluoroacetic anhydride (TFAA) during minutes to hours.[5]
We report an easy characterization of carboxylic-trifluoroacetic mixed anhydrides by 1H and 13C NMR
Summary
Esterification is a common procedure, widely reviewed,[1] to transform carboxylic acids or their derivatives into an ester functional group, to protect alcohols or to achieve molecular features. We report an easy characterization of carboxylic-trifluoroacetic mixed anhydrides by 1H and 13C NMR. Following the procedure above described for ATFAA, other carboxylic-trifluoroacetic anhydrides were prepared.
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