Chemoselective α‑Trifluoroacetylation of Amides Using Highly Electrophilic Trifluoroacetic Anhydrides and 2,4,6-Collidine

Chemoselective α-acylation of tertiary amides proceeded
with
highly electrophilic acid anhydrides and weak bases under mild conditions.
β-Ketoamides containing trifluoroacetyl or perfluoroacyl groups
were selectively obtained even in the presence of other functional
groups such as ketone, ester, etc. Density functional theory calculations
suggest that 1-acyloxyenamine is the key intermediate for the chemoselective
α-acylation.