The Cyano Group as a Traceless Activation Group for the Intermolecular [3+2] Cycloaddition of Azomethine Ylides: A Five‐Step Synthesis of (±)‐Isoretronecanol

The cyano group was used as a traceless activation group for the [3+2] cycloaddition of azomethine ylides in a two‐step process, thereby providing a highly effective approach to 5‐unsubstituted pyrrolidines. The transformation includes the silver acetate catalyzed intermolecular 1,3‐dipolar cycloaddition of α‐iminonitriles and an unprecedented sodium borohydride induced reductive decyanation reaction. A diverse array of substrates is amenable to this transformation. The methodology was further extended to a five‐step total synthesis of the pyrrolizidine natural product isoretronecanol.