Metal–Organic Framework Based on Copper and Carboxylate‐Imidazole as Robust and Effective Catalyst in the Oxidative Amidation of Carboxylic Acids and Formamides

Abstract

A metal-organic framework (MOF) based on copper and 1,3-bis(carboxymethyl)imidazole [Cu(bcmim)2] has been prepared up to gram-scale, using a precipitation methodology at room temperature. The MOF-Cu(bcmim)2 has proved to be a very efficient catalyst in the preparation of amides via an oxidative coupling between carboxylic acids and formamides in the presence of an oxidant, such as TBHP. The methodology for the preparation of amides has shown to be very robust regardless of the carboxylic acid, giving good conversions and selectivities. The heterogeneous catalyst has been recovered unaltered after the reaction, being easily separated from the reaction mixture and subsequently reactivated by suitable treatment. Moreover, the coupling reaction has been scaled up to gram-scale, being possible to prepare valuable products, such as fatty acid amides (i.e. 1-palmitoylpiperidine).

Comparative Study of Catalytic Systems Formed by Palladium and Acyl‐Substituted Imidazolium Salts

“…Regarding difunctionalized imidazole derivative, the synthesis of the zwitterion 1,3‐bis(carboxymethyl)imidazole (bcmim, 9 ) was performed by a multicomponent reaction between glycine and aqueous solutions of glyoxal and formaldehyde, isolating product 9 in 89% yield (Scheme ) . Subsequently, this zwitterion was transformed almost quantitatively into the corresponding imidazolium chloride 10 by acidic treatment (Scheme ).…”

Versatile Barium and Calcium Imidazolium‐Dicarboxylate Heterogeneous Catalysts in Quinoline Synthesis

“…In fact, catalyst bcmim‐Ba1 could be reused up to four times without appreciable loss of activity (entry 3), under both conventional and microwave heating. Partial deactivation of these heterogeneous catalysts could be due to the presence of by‐products remaining after the reaction . The standard washing (with EtOAc and Et 2 O) could be not sufficient to recover the original activity, and the use of other solvents and/or longer rinsing times may be required.…”

“…Partial deactivation of these heterogeneous catalysts could be due to the presence of by-products remaining after the reaction. [21] The standard washing (with EtOAc and Et 2 O) could be not sufficient to recover the original activity, and the use of other solvents and/or longer rinsing times may be required. Consequently, the barium-organic framework bcmim-Ba1 constituted the most rugged heterogeneous catalyst among those considered in the present study.…”

“…They can also be used in combination with metal salts, such as iron(III) chloride, to produce iron‐based Lewis acid ionic liquids (IBLAILs), which proved to be very versatile catalytic systems . Furthermore, we employed a metal‐organic framework based on imidazolium dicarboxylate as an efficient and robust catalyst for the oxidative coupling between carboxylic acids and formamides . On the other hand, the use of heterogeneous catalysts based on alkaline earth metals is quite scarce.…”

“…[20] Furthermore, we employed a metal-organic framework based on imidazolium dicarboxylate as an efficient and robust catalyst for the oxidative coupling between carboxylic acids and formamides. [21] On the other hand, the use of heterogeneous catalysts based on alkaline earth metals is quite scarce. Thus, following our interests, we have studied the catalytic activity of different heterogeneous catalysts based on alkaline earth, such as calcium and barium (bcmim-Ca and bcmim-Ba).…”