Convergent Synthesis of Functionalized Indolines from Alkyl Aryl Tertiary Amines and Diazoesters via Visible Light-Driven [4+1]-Annulation Approach

In this study, we present a novel methodology for synthesizing functionalized indolines. Our approach involves functionaliz-ing the sp3 C–H bond of amines through the ⍺-amino radical/iminium ion. This methodology does not rely on expensive metal catalysts, oxidants, photo-redox catalysts, and additives. Instead, it involves a visible-light-induced single-electron transfer (SET) and hydrogen atom-transfer (HAT) mediated [4+1]-annulation strategy between alkyl aryl tertiary amines and diazoesters. Mechanistic studies, including spin-trap, radical trap, and deuterium labeling experiments, have provided com-pelling evidence for the unique role of diazoester in this process. They act as an oxidant for SET, facilitate the generation of aminium ions from alkyl aryl tertiary amines, act as a HAT reagent/deprotonation for the generation of ⍺-amino radi-cal/iminium ion, and serve as a reactant to access the functionalized indolines. We have impressively synthesized a variety of substituted functionalized and polycyclic indolines. Importantly, we have also demonstrated the scalability of our approach through the successful scale-up reaction, indoline containing 1,3-bis diols, functionalized indoles synthesis stepwise, and one-pot from alkyl aryl amines.