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

Abstract

Quinoline and acridine derivatives have been prepared using a functionalized imidazolium salt as heterogeneous catalyst. Different ketones have been coupled with 2‐aminobenzaldehydes and 2‐aminoaryl ketones under solvent‐free conditions, employing 1,3‐bis(carboxymethyl)‐imidazolium chloride as a catalyst. The protocol is simple and effective for the synthesis of a variety of nitrogen containing heterocycles (> 35 examples) with moderate to excellent yields (up to 96 %), being possible to perform the reaction in preparative scale. Additionally, 3‐acetylquinolines have been transformed, under solvent‐free conditions, into quinolyl chalcone derivatives by means of the same catalyst. Thus, the catalytic system mediates both reactions effectively in a tandem procedure. Furthermore, the catalyst is easily separated from the reaction mixture and can be reused without loss of activity (up to 8 cycles) which remarks its sturdiness. The E‐factors are in the range of 14–23, both for the formation of quinolines and for the tandem reaction, which demonstrates the sustainability of the protocols described.

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

“…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.…”

“…We have proved that the imidazolium salt 1,3‐bis(carboxymethyl)imidazolium chloride ( bcmim‐Cl ), can be used as simple, efficient, regioselective and recyclable metal‐free catalyst for the preparation of N ‐allylanilines by allylic substitution of alcohols with anilines . Both the carboxyl and chloride moieties in the bcmim‐Cl are responsible of the favorable interactions with the reactants and key in the effective preparation of quinoline and acridine derivatives . We hypothesized that different counteranions in the imidazolium salt could result in a modification in the outcome of allylic substitution reaction of alcohols with anilines.…”

Recent synthetic efforts in the preparation of 2-(3,4)-alkenyl (aryl) quinoline molecules towards anti-kinetoplastid agents

“…Interest in the synthesis and chemistry of quinoline derivatives is not lost in our modern times, on the contrary, new methods and protocols for new quinoline molecules are constantly developing. 167,168 Always looking for more versatile and sustainable protocols, this development is now strongly related to the implementation of the concepts of green chemistry. Today, green construction of these heterocyclic molecules is the responsibility of organic chemists.…”

Ir(I)‐Catalyzed Synthesis of (E)‐4‐Benzylidenylacridines and (E)‐2‐Styrylquinoline‐3‐carboxamide through Sequential Suzuki–Miyaura Coupling, Dehydrogenative Friedländer Reaction, and sp3‐C–H Activation

“…In 2006, König et al reported that mannitol‐DMU‐NH 4 Cl (DES) mediated a Suzuki–Miyaura coupling reaction of biaryls using a palladium catalyst and Na 2 CO 3 as a base. Besides, literature protocols are available for Suzuki cross‐coupling reactions in DES . In 2019, Saavedra et al reported the Suzuki coupling reaction in ChCl:glycerol (1:2) utilizing a bipyridine‐palladium complex as a catalyst and NaHCO 3 as a base.…”