2015
DOI: 10.1039/c5cc02541a
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Base-free Knoevenagel condensation catalyzed by copper metal surfaces

Abstract: For the first time Knoevenagel condensation has been catalyzed by elemental copper with unexpected activity and excellent isolated yields. Inexpensive, widely available copper powder was used to catalyze the condensation of cyanoacetate and benzaldehyde under mild conditions. To ensure general applicability, a wide variety of different substrates was successfully reacted.

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Cited by 62 publications
(39 citation statements)
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“…Still, we rely on that the intermediate I was formed in the presence of ZnCl 2 , which undergoes Michael‐type addition with NMSM to give species II . Then, the intramolecular O‐cyclization of species II provides the desired compound 4 via intermediate III by the elimination of ─MeSH.…”
Section: Resultsmentioning
confidence: 99%
“…Still, we rely on that the intermediate I was formed in the presence of ZnCl 2 , which undergoes Michael‐type addition with NMSM to give species II . Then, the intramolecular O‐cyclization of species II provides the desired compound 4 via intermediate III by the elimination of ─MeSH.…”
Section: Resultsmentioning
confidence: 99%
“…Further, undesired side-reactions such as oligomerization may occur with relatively low reaction temperatures, and catalyst recovery is challenging. 6 As reported, the Knoevenagel condensation reaction 2,7,8 can take place on ethyl malonate (as substrate) bound to the Wang resin, however, product cleavage requires triuoroacetic acid, leading to excess pollution when it afforded pure coumarin-3-carboxylic acid derivatives. 9 To overcome those drawbacks mentioned above, numerous efforts have been made to develop better heterogeneous Knoevenagel catalysts, for example, metal-salt, nanoparticle catalyst, modied zeolites, ionic liquids or magnetic base analogues.…”
Section: Introductionmentioning
confidence: 95%
“…In addition, the electrical dynamic perturbation may have a role in the improvement of the transport properties and polarization of the reaction medium. The metallic (stainless steel type 316) electrodes themselves may have a role in this sequential Knoevenagel and hetero‐Diels–Alder reaction . Furthermore, the addition of NaCl to increase the medium conductivity and the initial heating rate may also have an effect in the reaction rate and selectivity.…”
Section: Ohmic Heating In Organic Synthesismentioning
confidence: 99%
“…The metallic (stainless steel type 316) electrodes themselves may have ar ole in this sequential Knoevenagel and hetero-Diels-Alder reaction. [33,34] Furthermore, the addition of NaCl to increaset he medium conductivity and the initial heatingr ate may also have an effect in the reaction rate and selectivity.I ti sr ecognized that salts with small cations are known to enhance the hydrophobic effect (saltingout effect) that could facilitate the Diels-Alder reactions in water. [35][36][37] Despite the low concentration of the salt aqueous solution (0.028 m)w hen compared to those described in the literature [35][36][37] we did not exclude this effect.…”
Section: Conceptmentioning
confidence: 99%