Banik, B.K., Banerjee, B., Kaur, G., Saroch, S. and Kumar, R., 2020. Molecules, 25(24), p.5918.
Screening suitable catalysts plays an important role in the synthesis of various heterocyclic entities. At present, scientists prefer metal-free organic catalysts to avoid metal contamination in synthetic products. Tetrabutylammonium bromide (TBAB) has attracted great attention as a highly efficient homogeneous transfer catalyst. In TBAB, tetrabutylammonium salt can be dissolved in both aqueous and organic solvents, which helps to transport water-soluble anionic reactants to the organic phase.
Synthesis of 1,4-Dihydropyridine Catalyzed by TBAB
A series of 1,4-dihydropyridine derivatives were synthesized through one-pot pseudo four-component Hantzsch reaction, in which one equivalent of various aryl or heteroaryl aldehydes, two equivalents of ethyl acetate, and one equivalent of ammonium acetate were reacted. 10 mol% TBAB was used as an efficient phase transfer catalyst, with a reaction temperature of 60 °C and reaction conditions in an aqueous medium. Diverse aromatic aldehydes with excellent yields produce the desired products.
Synthesis of 2,4,5-Triaryl Imidazoles Catalyzed by TBAB
Under the condition of reflux, the catalytic amount of TBAB isopropanol was used to synthesize 2,4,5-triaryl imidazoles. After the reaction is completed, the reaction medium containing TBAB is reused for further operation. Aldehydes with electron-donating and electron-absorbing substituents can obtain the desired products in extremely high yields. All reactions were completed within 30 minutes.
Synthesis of 1,3-Dihydrobenzimidazol-2-ones and 1H-imidazo[4,5-b]pyridin-2(3H)-one Catalyzed by TBAB
1,3-dihydrobenzimidazol-2-ones was synthesized efficiently from urea and o-phenylenediamine in ethanol using TBAB as catalyst. Under the optimized reaction conditions, pyridine-2,3-diamine reacted with urea to give the corresponding 1H-imidazo [4,5-b]pyridin-2(3H)-one with a yield of 68%. All reactions can be completed in 15 minutes.
Wen, Y., Wang, T., Cheng, J., Pan, J., Cao, G. and Yang, Y., 2012. Electrochimica acta, 59, pp.64-68.
Secondary zinc-based batteries usually limit their performance and extensive commercialization because of the poor cycle characteristics of zinc anodes. The short cycle life of zinc anode is mainly due to the dendrite growth and the change of zinc electrode shape during charging. Lead ion and tetrabutylammonium bromide (TBAB) have been proved to be inhibitors of spongy zinc electrogrowth in mobile alkaline zincate solution.
Effects of Pb (II) and TBAB on Spongy Growth of Zinc
Adding TBAB to the electrolyte results in a flatter current-time response. With the increase of TBAB concentration, the increase of deposition current decreased during the test period. At the beginning of zinc deposition, a sharp decrease in current was observed, which may be caused by the formation of crystal nuclei. The higher the concentration of TBAB, the more obvious this phenomenon is. When the concentration of TBAB additive is 10-4 M or more, the current-time curve is almost flat. When the content of TBAB in the electrolyte is 10-4 M, the current-time curve is not only almost flat, but also the cathodic deposition current is close to the initial current in the blank solution. This shows that the addition of 10-4 M TBAB can effectively inhibit the formation of sponge zinc and does not significantly reduce the charging efficiency of the deposited zinc electrode.
Similar to the case of adding TBAB, the inhibition effect of lead ion on sponge zinc increased with the increase of lead concentration.
Synergistic Effect of Pb (II) and TBAB
At higher magnetic stirring speed, the mixed addition of lead ion and TBAB was further studied. The addition of 10-4 M lead ion or TBAB alone produced a gentle current-time response, but the increase of cathodic current was still obvious, especially the addition of TBAB. The almost flat current-time curve showed that the double addition of lead and TBAB produced a synergistic effect, and the optimum concentration was 10-4. This shows that the mixed addition of lead ion and TBAB has stronger corrosion inhibition ability to sponge zinc.
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