We selected the synthesis of amide 1 as a test reaction for evaluating a range of ester solvents. Using 10 mol% B(OCH2CF3)3 catalyst, the reaction could be performed in a range of ester solvents under Dean-Stark reaction conditions though the yields were somewhat variable (Table , entries 2-7). A very low yield was obtained in ethyl acetate (entry 2), and n-propyl acetate (entry 3) or n-butyl acetate (entry 4) offered relatively little improvement. Pleasingly, iso-propyl acetate (entry 5) and tert-butyl acetate (entry 6) gave significantly improved yields with the latter being particularly effective, even though these solvents have lower boiling points than their unbranched isomers. The yield of amide 1 could be further improved in tertbutyl acetate by increasing the concentration of the reaction mixture to 1 M, leading to a reduction in the solvent requirements of the process. Finally, the nitrile solvents propionitrile (entry 8) and butyronitrile (entry 9) were also effective for the amidation reaction, potentially offering useful more-polar alternative solvents. It should be noted that the most effective solvents have relatively low boiling points and form azeotropes with a high proportion of water present, with tert-butyl acetate (bp 97 °C; 22 wt% H2O in azeotrope) and propionitrile (bp 97 °C; 24 wt% H2O in azeotrope) being most effective. 11 This may reflect a balance between the need for efficient water removal from the reaction and the greater levels of catalyst decomposition which may take place at higher reaction temperatures. A selection of other simple amidation catalysts (entries 10-13) were also evaluated in t BuOAc, with only an arylboronic acid being effective. Scheme 2: Scope of the catalytic amidation reaction in tert-butyl acetate. All reactions were performed using 10 mol% catalyst unless otherwise indicated. Yields given in parentheses/brackets are for the synthesis of the same amide in TAME/PhMe.