Copper‐Catalyzed Three‐Component Synthesis of 2‐Iminodihydrocoumarins and 2‐Iminocoumarins

Abstract

An efficient synthesis of N-sulfonyl-substituted 2-imino-3,4-dihydrocoumarins and 2-iminocoumarins via a copper-catalyzed multicomponent reaction of sulfonyl azides with terminal alkynes and b-(ortho-hydroxyphenyl)-a,b-unsaturated ketones or ortho-hydroxyphenylpropiolates has been developed. The cascade process involves trapping the keteimine by a nucleophilic addition and an intramolecular Michael addition. This methodology could well be extended to the concise synthesis of the polysubstituted piperidine scaffold.

Application of the polyacrylonitrile fiber as a support for the green heterogeneous base catalyst and supported phase-transfer catalyst

“…23,24 Nevertheless, most of the currently used methods for the synthesis of iminocoumarins suffer from several shortcomings, including the use of non-recoverable catalysts, highpower microwaves, long periods of reaction time, troublesome procedures as well as limited substituents. [25][26][27] Exploiting efficient approaches to iminocoumarins would be of great interest and value. Thus the efficacy of the PANF-PA function as heterogeneous base catalyst was evaluated via Knoevenagel condensation-cyclization between salicylaldehydes and activated nitriles to afford a wide variety of iminocoumarins (Scheme 2).…”

Preparation of 1,2-substituted benzimidazoles via a copper-catalyzed three component coupling reaction

“… 14 The ketenimine intermediate generated by copper-catalyzed terminal alkyne and sulfonyl azide could be take reaction simultaneous employing of pronucleophiles (Nu–H) and electrophiles (E) by designing the substrates. The o -hydroxy or o -amino electrophiles-containing benzene was the best strategy for the substrates, such as salicylaldehydes/ o -hydroxyl-acetophenones, 15 2-acetyl aniline, 16 phenolic schiffs' bases, 17 α-( ortho -hydroxyphenyl)-α,β-unsaturated ketones/ o -hydroxy-phenylpropiolates, 18 o -hydroxybenzonitrile 19 ( Scheme 1a ) etc . However, two pronucleophiles (Nu–H) simultaneous nucleophilic addition with the ketenimine intermediate is rare.…”

Copper-Catalyzed Diversity-Oriented Synthesis (DOS) of 4-Amino-2H-chromen-2-imines: Application of Kemp Elimination toward O-Heterocycles

“…16 Copper-catalyzed tandem cyclization of ketenimine intermediates with different dipole nucleophile–electrophile building blocks such as 2-hydroxylacetophenones and 2-hydroxyphenylpropiolates has so far been explored to construct 2-iminocoumarins or similar fused O-heterocycles. 17 Recently, the Zhang and Yi’s group reported an expedient synthesis of 4-amino-2 H -chromen-2-imines by the combination of copper-catalyzed CuAAC reaction with 2-hydroxybenzonitriles. 18 The development of novel dipole nucleophile–electrophile building blocks for difunctionalization of the intermediate species can be expected, thus expanding the synthetic applications of useful cyclic molecules in step-economic domino reactions.…”

“…The key to the success of CuAAC is the in situ generation of a reactive ketenimine intermediate, which could be chemo- and regioselectively transformed into various heterocyclic molecules as disclosed by the groups of Chang and Wang, and recently among others . Copper-catalyzed tandem cyclization of ketenimine intermediates with different dipole nucleophile–electrophile building blocks such as 2-hydroxylacetophenones and 2-hydroxyphenylpropiolates has so far been explored to construct 2-iminocoumarins or similar fused O-heterocycles . Recently, the Zhang and Yi’s group reported an expedient synthesis of 4-amino-2 H -chromen-2-imines by the combination of copper-catalyzed CuAAC reaction with 2-hydroxybenzonitriles .…”