1,3-Bis(carboxymethyl)imidazolium Chloride as a Metal-Free and Recyclable Catalyst for the Synthesis of N-Allylanilines by Allylic Substitution of Alcohols

Abstract

in preparative scale [e.g. 3.30 g of N-(1,3-diphenylallyl)-4-nitroaniline]. The catalyst could be reused up to 15 cycles without loss of activity, proving its robustness.

Anion‐Dependent Imidazolium‐Based Catalysts for Allylation of Aniline with Tunable Regioselectivity

“…The temperature has also an influence in the reaction selectivity. In our previous work, we proved that both the ortho ‐ and the para ‐allylanilines (i. e. 4 aa and 5 aa ) can be formed, in low selectivity, from the N ‐allyl substituted product 3 aa by increasing the temperature and the reaction time (Table , entries 4 and 5), using bcmim‐Cl as catalyst. Interestingly, the use of the imidazolium iodide analogue as catalyst (10 mol%) in our model reaction, resulted in a drastic change in the selectivity and product 5 aa was formed in 77% conversion after 6 h (Table , entry 11).…”

“…This catalysts deactivation could be attributed to their degradation. It has been proven that the effectiveness of the catalyst depends, in part, on the halide, bearing in mind that the zwitterion [1,3‐bis(carboxymethyl)imidazole, bcmim ] is inactive for this type of transformation . We pondered the premise that the amount of halide could decrease during the reaction and/or the work‐up, the less bound the halide is to the cation, the easier the dissociation.…”

“…Likewise, the amount of bromide in bcmim‐Br was reduced to less than 11%, compared with a fresh sample, after the fifth cycle. For comparison, a recycled sample of bcmim‐Cl , which holds its activity for 15 cycles, contains 16% of the initial amount of chloride after fifteen cycles . Although, the higher robustness of the chloride salt is vindicated, it should be noted that the reactivation of all three different catalysts can be easily performed by treatment in the corresponding acid medium.…”

“…Considering that the reactions are performed in the absence of any solvent, it is postulated that the catalysts facilitate the interactions between the reactants. The presence of the carboxy groups in the imidazolium catalyst, that enables the formation of hydrogen bonds with the reagents, is key to the catalytic process, although the interaction of the halide with the reagents appears to be also crucial . Thus, it can be proposed that these bcmim‐X salts, which are ionic organic solids (IOS), establish favorable interactions by acting both as hydrogen donors and hydrogen acceptors.…”

Effective and Sustainable Access to Quinolines and Acridines: A Heterogeneous Imidazolium Salt Mediates C–C and C–N Bond Formation

“…According to our research work on the use of catalytic systems based on carboxy‐functionalized imidazole derivatives, we considered the possibility of using 1,3‐bis(carboxymethyl)imidazolium chloride ( bcmim‐Cl ) as a heterogeneous catalyst in the coupling of 2‐aminophenyl‐carbonyl compounds with ketones for the synthesis of quinolines. This salt bcmim‐Cl is an ionic organic solid (IOS), which can be then more easily separated from the reaction mixture . Moreover, we hypothesized that the functionalized imidazolium salt can establish favorable interactions with the reactants, in a similar way that occurs with the components of a low transition temperature mixtures (LTTM) or deep eutectic solvents (DES), favoring the reaction between reactants in the absence of any solvent (Figure ).…”