Advances on the Synthesis and Application of α,β-Unsaturated Nitrones

Abstract

Nitrones, served as one of the most important 1,3-dipoles in organic synthetic chemistry, can participate in various organic synthetic reactions to synthesize various heterocyclic compounds, such as nucleophilic addition, cycloaddition reaction, rearrangement reaction, C-H bond activation, etc. They are very important organic building blocks for the further construction of complex molecules. In recent years, α,β-unsaturated nitrone has attracted widespread attention from synthetic chemists because of its α,β-unsaturated bond containing rich chemical transformations, and can take part in various new chemical conversions to construct new structural heterocyclic compounds. The new strategies for the preparation of α,β-unsaturated nitrones in the past ten years, and their applications to construct nitrogen heterocyclic compounds, including O-transfer reaction, addition of nucleophiles and radical reagents, and various cycloaddition reactions, are reviewed.

Cinchonidine-Catalyzed Synthesis of Oxazabicyclo[4.2.1]nonanones from N-Aryl-α,β-unsaturated Nitrones and 1-Ethynylnaphthalen-2-ols

“…In 2020, Jiang and co-workers reported a [4 + 3] cycloaddition of nitrones with 1-ethynylnaphthalen-2-ols and subsequent [3,3]-rearrangement of N–O bonds and dehydration to afford polycyclic indoles by quinine catalysis (Scheme -A) . Based on the easily dearomative 1-ethynylnaphthalen-2-ols and our studies of the reactivity of α,β -unsaturated nitrones, , we proposed that a hydrogen-bonding bifunctional catalyst could catalyze the cycloaddition of α,β-unsaturated nitrones to vinylidene o -quinone methides generated from 1-ethynylnaphthalen-2-ols to produce seven-membered N–O vinyl intermediates. Then it will undergo a selective [1,3]-rearrangement on the N -atom rather than a [3,3]-rearrangement on the phenyl ring owing to the lower steric hindrance of the styrenyl group connecting to the N , O -acetal .…”

Synthesis of N-Vinyl Cinnamaldehyde Nitrones through Atropisomeric Quinoxaline-Derived N,N,O-Ligand-Promoted Chan-Lam Reaction

“…Nitrones, as an important class of 1,3-dipoles in cycloaddition, have been extensively used as building blocks in the construction of various heterocycles . Some of them have been successfully applied in the total synthesis of natural products by [3 + 2] cycloaddition .…”

Synthesis of Azetidine Nitrones and Exomethylene Oxazolines through a Copper(I)-Catalyzed 2,3-Rearrangement and 4π-Electrocyclization Cascade Strategy

“…Nitrone not only serves as an important unit in natural products and biologically active molecules but also is extensively used as a useful 1,3-diploe toward the construction of N-heterocycles in organic synthesis . Many strategies have been developed to prepare acyclic nitrones through condensation, oxidation, elimination, or coupling reactions, and so on.…”