Ketenimines are an important class of reactive species and useful synthetic intermediates. During the last two decades several practical and versatile approaches to ketenimines have been developed, leading to exhaustive investigations on ketenimine chemistry and the discovery of a variety of highly efficient reactions. Five types of reactions for ketenimines have been reported, including nucleophilic additions (ketenimines can be used as both electrophiles and nucleophiles), radical additions, cycloaddition reactions, electrocyclic ring closure reactions, and σ rearrangements. Furthermore, numerous complex organic compounds, particularly the biologically interesting heterocycles, have been constructed using these methodologies. The review of these accomplishments is presented here.

The thriving chemistry of ketenimines

Structurally diverse pyridinium salts are quite familiar structures in many natural products and bioactive pharmaceuticals. Over the centuries, these privileged scaffolds have played an intriguing role in a wide range of research topics and, thus, this review aims at highlighting the pyridinium salts in terms of their synthetic routes, reactivity and their importance as pyridinium ionic liquids, as pyridinium ylides, as anti-microbial, anti-cancer, anti-malarial and anti-cholinesterase inhibitors, as well as their applications in materials science and biological issues related to gene delivery.

Pyridinium salts: from synthesis to reactivity and applications

Progress in 1,3-dipolar cycloadditions in the recent decade: an update to strategic development towards the arsenal of organic synthesis

Synthesis of 2-Aminoindolizines by 1,3-Dipolar Cycloaddition of Pyridinium Ylides with Electron-Deficient Ynamides

Highly controlling selectivity of copper(I)-catalyzed azide/alkyne cycloaddition (CuAAC) between sulfonyl azids and normal alkynes or propynoates

A series of 4-arylsulfonylimino-4,5-dihydrofurans (14 examples) were efficiently synthesized in good to excellent yields by using the copper-catalyzed three-component reaction between sulfonyl azides, phenylacetylene, and β-ketoesters in tetrahydrofuran (THF) at 40 °C for 8 h in the presence of triethylamine (TEA). A plausible mechanism for this process is proposed.

Copper-Catalyzed Multicomponent Reaction: Synthesis of 4-Arylsulfonylimino-4,5-dihydrofuran Derivatives

New route synthesis of indolizines via 1,3-dipolar cycloaddition of pyridiniums and alkynes

DMAP-catalyzed cascade reaction: one-pot synthesis of benzofurans in water

A facile and efficient synthesis of N-sulfonyl-N,N-disubstituted amidines has been achieved via a CuI-catalyzed three-component free-radical coupling reaction of tertiary amines and arenesulfonyl azides with terminal alkynes in the presence of azodiisobutyronitrile (AIBN). The reaction mechanism of this reaction has also been studied.

Syntheses of N-sulfonyl-N,N-disubstituted amidines via a three-component free-radical coupling reaction of tertiary amines and arenesulfonyl azides with terminal alkynes

A series of benzofurans were efficiently synthesized in good to excellent yields using 4-dimethylaminopyridine (DMAP) catalyzed cascade reaction between salicylaldehydes and halogenated ketones in water at 80 °C opened atmosphere.

Kai Ju

Papers

Copper-Catalyzed Multicomponent Reaction: Synthesis of 4-Arylsulfonylimino-4,5-dihydrofuran Derivatives

New route synthesis of indolizines via 1,3-dipolar cycloaddition of pyridiniums and alkynes

DMAP-catalyzed cascade reaction: one-pot synthesis of benzofurans in water

Syntheses of N-sulfonyl-N,N-disubstituted amidines via a three-component free-radical coupling reaction of tertiary amines and arenesulfonyl azides with terminal alkynes

DMAP-Catalyzed Cascade Reaction: One-Pot Synthesis of Benzofurans in Water.