Visible-Light-Mediated (sp³)Cα–H Functionalization of Ethers Enabled by Electron Donor–Acceptor Complex

Abstract

A synthetically beneficial visible-light-mediated protocol has been disclosed to achieve C−H amination of readily available feedstocks cyclic and acyclic ethers. A rarely identified Nbromosuccinamide−tetrahydrofuran electron donor−acceptor complex served as an initiator to functionalize both α-diazoketones and dialkyl azodicarboxylates. This developed methodology gives an alternative and milder way to construct the C−N bond and can be explored for the formation of C−C bond to perform arylation and allylation reactions.

Visible-Light-Induced Oxyalkylation of 1,2,4-Triazine-3,5(2H, 4H)-diones with Ethers via Oxidative Cross-Dehydrogenative Coupling

“…Therefore, it would be a challenging but highly attractive task to explore a mild and transition-metal-free methodology for cross-dehydrogenative-coupling (CDC) α-C–H bond of diverse ethers avoiding the use of peroxides. Recently, visible-light-induced functionalization of the C–H bond has gained a lot of attention as an eco-friendly access to a wide variety of organic scaffolds . Organic dyes, such as eosin Y, rose bengal (RB), 2- tert -butylanthraquinone (2- t -Bu-AQN), have been recognized as perfect alternatives to transition-metal catalysts due to their inexpensiveness, excellent photocatalytic performance, and low toxicity features.…”

Exploiting N-Centered Umpolung Reactivity of α-Iminomalonates for the Synthesis of N-Sulfenylimines and Sulfonamides

“…A significant red-shift occurred in the visible spectral region in its optical absorption spectrum while adding NaOAc to this mixture, diagnostic of an electron-donor–acceptor (EDA) complex between iminomalonate 1i and benzenethiolate ( 2a -Na) (see Supporting Information section 5.2 for the UV–visible data). Based on literature precedence, , we contemplated that the formation of EDA complex must direct the reaction toward a radical pathway. A radical scavenging experiment was performed by adding (2,2,6,6-tetramethylpiperidin-1-yl)­oxyl (TEMPO) to the reaction mixture, where an increasing amount of TEMPO led to a diminishing yield of product 3u .…”

Visible-Light-Induced Hydrogen Atom Transfer En Route to Exocylic Alkenylation of Cyclic Ethers Enabled by Electron Donor–Acceptor Complex

“…In this context, several reports were also documented where the photocatalyst undergoes oxidative quenching to assist the peroxy radical formation for desired hydrogen atom abstraction . Apart from oxygen radical-based HAT reagents, nitrogen-centered radicals from N -hydroxy succinimides, thiyl radicals from thiols, conjugated ketyl radicals from aromatic ketones, and halogen radicals produced from halide salts are also frequently used for abstracting the hydrogen atom from the C­(sp 3 )–H bond . Despite having this broad library of attractive synthetic procedures for ether functionalization, most of the aforementioned methods suffer from several shortcomings.…”