Chemoselectivity in Esterification Reactions – Size Matters after All

Dedicated to Herbert Mayr on the occasion of his 70^th birthday

Abstract

The reaction of carboxylic acid chlorides with secondary alcohols carrying either flexible alkyl or rigid aryl substituents was studied through a series of competition experiments. Aliphatic acid chlorides react preferentially with the aryl-substituted alcohols, while acid chlorides derived from aromatic carboxylic acids react with very low selectivity. Catalysis by 9-azajulolidine (TCAP) increases the selectivity strongly, while solvent and temperature effects are only moderate. The size of the alcohol substituents seems to impact selectivities only for rigid aryl substituents, and highest selectivities have been found for 1-(1-pyrenyl)ethanol.

Key words

chemoselective esterification - acyl chlorides - organocatalysis - competition experiments - dispersion energy donor

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