Highly StereoselectiveSynthesis of α‑Oxoketene <i>N,X</i>-Acetals(<i>X</i> = O, S, or N) under MildConditions

A straightforward synthesis of α-oxoketene <i>N,X</i>-acetals (<i>X</i> = O, S, or N) from β-oxoamides has been described. The oxyphosphonium intermediates are quickly generated <i>in situ</i> from β-oxoamides in the presence of Hendrickson reagent and triflic anhydride (Tf₂O) in a chemoselective manner and undergo a chemoselective nucleophilic substitution with phenols, thiophenols, or aromatic amines to deliver the desired products with high stereoselectivity. The one-pot synthetic protocol features readily available starting materials, mild conditions, simple execution, and a wide range of synthetic potentials of the products.