NaI/PPh₃-catalyzed visible-light-mediated decarboxylative radical cascade cyclization of N-arylacrylamides for the efficient synthesis of quaternary oxindoles

Abstract

A practical NaI/PPh3-catalyzed decarboxylative radical cascade cyclization of N-arylacrylamides with redox-active esters is described, which is mediated by visible light irradiation. A wide range of substrates bearing different substituents and derived from ubiquitous carboxylic acids, including α-amino acids, were synthesized and examined under this very mild, efficient, and cost effective transition-metal-free synthetic method. These afforded various functionalized oxindoles featuring a C3 quaternary stereogenic center. Mechanistic experiments suggest a radical mechanism.

Silver-Catalyzed Cascade Radical Bicyclization Reaction: An Atom- and Step-Economical Strategy Accessing γ-Lactam Containing Isoquinolinediones

“…Next, formed intermediate B undergoes a radical addition to the double bond of 2a , generating a new radical C . This radical C underwent another intramolecular cyclization to form the intermediate D . Finally, D is oxidized by Ag­(II) via a single electron transfer (SET) process, accompanied by deprotonation, ultimately yielding desired product 3aa .…”

Recent advancements in iodide/phosphine-mediated photoredox radical reactions

“…Recently, independent research groups led by Li, Yang, and Patureau separately disclosed a novel approach to 3,3-disubstituted oxindoles 43 through an iodide/phosphine-catalyzed visible-light-mediated decarboxylative radical cascade cyclization of N -arylacrylamides 42 ( Scheme 18 ) [ 35 – 36 ]. Importantly, these methodologies could also be smoothly extended to the synthesis of isoquinolinediones, which borne a quaternary carbon center.…”

Photodecarboxylative C–H Alkylation of Azauracils with N-(Acyloxy)phthalimides

“…In this regard, Shang, Fu, and co-workers’ pioneering work on the photoinduced sodium iodide/triphenyl phophine-mediated alkylation of silyl enol ethers using NHPI esters captivated our attention . This method is particularly noteworthy, as it required a readily available, stable, and inexpensive donor system for the formation of an EDA complex under blue light irradiation and has exhibited immense applicability in a variety of alkylation processes . Accordingly, herein, we report a triphenylphosphine and sodium iodide-mediated alkylation of azauracils using NHPI esters under blue light-emitting diode irradiation (Scheme d).…”