This journal is © 2020 The Royal Society of Chemistry. The nucleophilic γ-phenylation and γ-alkylation of α,β-unsaturated amides have been developed. This umpolung reaction allows the regioselective introduction of phenyl and alkyl groups to a vinylketene N,O-acetal, which is generated in situ from an α,β-unsaturated N-alkoxyamide, followed by N-O bond cleavage in a two-step, one-pot process.