Photoredox-Catalyzed Synthesis of α-Amino Acid Amides by Imine Carbamoylation

Abstract

An operationally simple protocol for the photocatalytic carbamoylation of imines is reported. Easily available, bench-stable 4-amido Hantzsch ester derivatives serve as precursors to carbamoyl radicals that undergo rapid addition to N-aryl imines. The reaction proceeds under blue light irradiation in the presence of the photocatalyst 3DPAFIPN and Brønsted/Lewis acid additives. Mechanistic studies indicated a photoredox mechanism that involves carbamoyl radicals.

Visible-light-mediated synthesis of α,β-diamino esters via coupling of N,N-dimethylanilines and glyoxalic oxime ethers

“…However, the direct α-aminoalkylation of glyoxalic oxime ethers using dimethylaniline remains unexplored. [31][32][33] Herein, we report the development of a Ru(bpy) 3 Cl 2 catalyzed, visible-light-mediated protocol for the synthesis of α,β-diamino esters via the coupling of glyoxalic oxime ethers and dimethylanilines. The reac-tion is general, employs readily available precursors and proceeds under mild conditions (Scheme 1d).…”

Photoinduced carbamoylation reactions: unlocking new reactivities towards amide synthesis

“…Following this publication by Paixa ˜o, Von Wangelin and co-workers reported a similar protocol, using imines 27 as radical acceptors, using BF 3 OEt 2 as a Lewis acid additive (Scheme 16). 79 Very recently, Wang and co-workers, inspired by the noteworthy importance of itaconate and its derivatives in the immune metabolism of inflammation and tumor via cysteine-protein conjugation via Michael reactions, developed a site-selective Scheme 14 Photoinduced synthesis of C4-functionalized pyridines and quinolones from N-amido pyridinium salts, using DHPs as radical sources and some selected examples of carbamoylated products.…”

“…Following this publication by Paixão, Von Wangelin and co-workers reported a similar protocol, using imines 27 as radical acceptors, using BF 3 OEt 2 as a Lewis acid additive (Scheme 16). 79…”

Taming photocatalysis in flow: easy and speedy preparation of α-aminoamide derivatives

“…The motif comprises an amine, a carbonyl group, and tunable substituents at the β- or even at the α-position. Unsurprisingly, several retrosynthetic disconnections might be suggested when sketching possible synthetic routes, which can be summarized in three main approaches: (1) amide bond formation (Scheme 1, magenta box); 5 (2) addition of a carbamoyl radical 6 or an anion 7 to imines (Scheme 1, blue box); and (3) electrophilic α-amination via an enol 8 (Scheme 1, yellow box).…”