Chemoselective transformations are acornerstone of efficient organic synthesis;h owever,a chieving this goal for even simple transformations,s uch as acylation reactions,i s often achallenge.W ereport that N-carbonylimidazoles enable catalytic chemodivergent aniline or alcohol acylation in the presence of pyridinium ions or 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), respectively.B oth acylation reactions display high and broad chemoselectivity for the target group.U nprecedented levels of chemoselectivity were observed in the DBUcatalyzede sterification:Asingle esterification product was obtained from amolecule containing primary aniline,alcohol, phenol, secondary amide,a nd N À Hi ndole groups.T hese acylation reactions are highly practical as they involve only readily available,inexpensive,and relatively safe reagents;can be performed on am ultigram scale;a nd can be used on carboxylic acids directly by in situ formation of the acylimidazole electrophile.

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Chemoselective transformations are a cornerstone of efficient organic synthesis; however, achieving this goal for even simple transformations, such as acylation reactions, is often a challenge. We report that N‐carbonylimidazoles enable catalytic chemodivergent aniline or alcohol acylation in the presence of pyridinium ions or 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU), respectively. Both acylation reactions display high and broad chemoselectivity for the target group. Unprecedented levels of chemoselectivity were observed in the DBU‐catalyzed esterification: A single esterification product was obtained from a molecule containing primary aniline, alcohol, phenol, secondary amide, and N−H indole groups. These acylation reactions are highly practical as they involve only readily available, inexpensive, and relatively safe reagents; can be performed on a multigram scale; and can be used on carboxylic acids directly by in situ formation of the acylimidazole electrophile.