Novel Hybrid Prins/Aza‐Prins Oxocarbenium/N‐Acyliminium Cascade: Expedient Access to Complex Indolizidines

Abstract Heavy silyl enol ethers (mostly TIPS and TBS) combine with cyclic N ‐alkenyl N ‐acyliminium salts generated in situ from their N,O‐acetal precursors, to furnish highly functionalized indolizidines through an unprecedented double Mukaiyama–Mannich–Prins cascade transformation. This novel cascade annulation process demonstrates a promising scope, and takes place mostly catalytically with interesting stereocontrol. Furthermore, an appealing facet of this chemistry is emphasized with a bicatalytic approach by which the Mannich–Prins cascade follows a Ru‐catalyzed N ‐allylamide to N ‐( E )‐propenyl isomerization of the aminal counterpart in a one‐pot operation.