Photocatalytic Azetidine Synthesis by Aerobic Dehydrogenative [2 + 2] Cycloadditions of Amines with Alkenes

Abstract

Photocatalytic dehydrogenative [2 + 2] cycloadditions between amines and alkenes were developed that allow for the stereoselective and high-yielding synthesis of functionalized azetidines. The oxidative formal Aza Paternò–Büchi reactions are induced by photoredox-catalyzed aerobic oxidation of dihydroquinoxalinones 1 as the amines, and in the presence of structurally diverse alkenes 3 intermolecular [2 + 2] cyclization to dihydro-1H-azeto[1,2-a]quinoxalin-3(4H)-ones 4 occurs. The utility of the method is illustrated by the selective conversion of amino acid derived dihydroquinoxalinones 1, including oxidation-prone lysine and tryptophan derivatives.

Photocatalysis as a green alternative toolkit for the construction of nitrogen-enriched heterocycles via the direct and indirect activation of alkynes/alkenes

“…Brasholz et al developed [2 + 2] cycloadditions between amines ( 776 ) and alkenes ( 778 ) that enable the stereoselective and high-yield production of functionalized azetidine ( 779 ) (Table 21L). 128 This study employed a two-stage, one-pot synthetic method, with the first phase involving converting amine ( 776 ) to imine ( 777 ) and the second involving cyclization. In this case, the iridium photocatalyst ( PC23 ) functioned as both a photoredox catalyst and a photosensitizer.…”

A Selenium Atom Involved Covalent Organic Framework for Window Ledge Photocatalytic Oxidation of Sulfides

“…The photo‐chemical conversion technology has attracted lots of attentions, which can take full advantage of the sustainable solar energy and alleviate the energy crisis. [ 1 ] As one of the most important applications, visible light driven photocatalytic organic transformations such as cycloaddition reaction, [ 2 ] photooxidation of sulfides [ 3 ] and aerobic cross‐dehydrogenative coupling (CDC) reaction [ 4 ] have exhibited great potential in the field of organic photosynthesis, which provides an eco‐friendly and energy‐saving platform for the “green” synthesis of chemical intermediate products and biological pharmaceutical agents. [ 5 ] To achieve high organic transformation efficiency, photocatalysts should be rationally designed and possess strong extinction coefficient, high exciton dissociation efficiency and fast charge‐transfer properties to effectively initiate the electron or hole injection process of the catalytic system.…”

Navigating Visible‐Light‐Triggered (aza and thia) Paternò‐Büchi Reactions for the Synthesis of Heterocycles

“…In 2022, Brasholz and co-workers studied intermolecular oxidative formal aza Paternò-Büchi reactions between dihydroquinoxalinones and diverse alkenes with 2 mol % Ir(ppy) 3 , and in the presence of air to yield functionalized azetidines (Scheme 15). [26] Based on the mechanism study, the authors proposed two reaction pathways. Path I was the [2 + 2] cycloaddition of energy transfer via triplet biradical intermediate to azetidines; path II was radical/polar crossover cyclization to azetidines.…”