2‐Hydroxy‐3‐(Pyrrolidin‐1‐yl)‐Indolines: A Platform for Accessing Decorated Deaminokynurenines Enabled by a Double Tautomeric Control

Abstract In this study we introduce indoline hemiaminals as phenacyl bromide surrogates for the synthesis of deaminokynurenine derivatives through cyclic‐linear tautomeric intermediates. The reaction proceeds through a tandem process involving the ring opening of indoline hemiaminals, generating transient acyclic aldehydes which are then trapped with in situ generated enolate species. Our protocol overcomes traditional dilemma in production of polar‐mismatch 1,4‐dicarbonyl compounds by utilizing a transient highly electrophilic linear aldehyde and late‐stage transposition of carbonyl moiety. The synthetic utility of our transformation was demonstrated by follow‐up transformations, including the first total synthesis of quinoline‐2,4‐dione alkaloid.