A Primary Amide-Functionalized Heterogeneous Catalyst for the Synthesis of Coumarin-3-carboxylic Acids via a Tandem Reaction

Abstract

A crystalline primary amide-based bifunctional heterogeneous catalyst, {[Cd 2 (2-BPXG)(Fum) 2 (H 2 O) 2 ]•2H 2 O} n (1) (where, 2-BPXG = 2,2′-((1,4-phenylenebis(methylene)) bis((pyridin-2-ylmethyl)azanediyl)) diacetamide and Fum = fumarate), has been developed for the one-pot synthesis of a series of potentially biologically active coumarin-3-carboxylic acids at room temperature via a Knoevenagel-intramolecular cyclization tandem reaction. Catalyst 1 is prepared at room temperature from a one-pot self-assembly process in 81% yield and high purity within a few hours and has a ladder-like polymeric architecture based on single-crystal X-ray diffraction. Additional characterization of 1 includes elemental analysis, infrared spectroscopy, thermogravimetric analysis, and powder X-ray diffraction. Based on the optimized conditions, it is determined that 1 is highly efficient (conditions: 2 mol % catalyst, 3 h, and 26−28 °C in methanol) for this reaction. Its recyclability up to five cycles without significant loss of activity and structural integrity is also demonstrated. Using both electron-donating and electron-withdrawing substituents on the salicylaldehyde substrate, seven different derivatives of coumarin-3-carboxylic acid were made. Additionally, the monoamine oxidase (MAO) inhibitor, coumarin-3-phenylcarboxamide, has also been synthesized from coumarin-3-carboxylic acid obtained in the catalysis process. A detailed mechanism of action is also provided.

CdO Nanostructures as Acid–Base Bifunctional Heterogeneous Catalysts for Making Coumarin-3-carboxylic Acids at Room Temperature

“…33 Furthermore, its ester and amide derivatives are also biologically valuable. 34 Considering the importance of coumarin-3-carboxylic acids, among the several pathways the most exploited method is the Knoevenagel-Intramolecular cyclization tandem reaction of substituted ortho-hydroxyaryl aldehydes and Meldrum's acid aided by a variety of catalysts. 35 Until recently, its synthesis involved mainly homogeneous catalysts, such as FeCl 3 36 and ammonium acetate.…”

“…It also plays an important role in the field of neurology for various disorders such as epilepsy and chronic nerve pain . Furthermore, its ester and amide derivatives are also biologically valuable …”

“…Therefore, it objects to the economic significance of the catalytic procedure. On the other hand, the utilization of acid clay (montmorillonitric clay) catalyst, 38 Yb(OTf) 3 , 39 NaNbO 3 40 as well as a metal−organic framework (MOF), Cd-MOF; 34 as heterogeneous catalysts for this reaction is limited. Additionally, these also have some limitations due to higher catalyst amount (up to 8 mol %), reaction time (up to 24 h), or the requirement of external energy source (microwave radiation).…”

A paradigm shift in the room-temperature self-assembly of tunable metal–organic frameworks composed of flexible neutral linkers with six N-donor atoms and a curved dicarboxylate

“…For some time, our group has been exploring the eld with the goal of generating diverse MOFs from three components, where a suitable combination of exible neutral bis(tridentate) linkers with six N-/O-donor atoms and readily available dicarboxylates is reacted with metal salts in a self-assembly process under ambient conditions. [26][27][28][29][30][31][32][33] We have also developed an understanding of the role played by the ratio of the metal ion, and neutral and anionic multitopic linkers in the self-assembly process to obtain such MOFs. With a bis(tridentate) ligand, a 1 : 1 ratio of a metal salt to the ligand generates either a discrete mononuclear complex or a polymer, both of which do not allow the third component like a dicarboxylate to bind to the hexacoordinated metal center for a desired three-component MOF; on the other hand, a 2 : 1 ratio of a metal salt to the ligand provides each metal center of the dimetal subunit with open coordination sites for the binding of the third component like a dicarboxylate (Scheme S1 †).…”

Two Zn(II)/Cd(II) Coordination Polymers as Recyclable Heterogeneous Catalysts for an Efficient Room-Temperature Synthesis of α-Aminonitriles via the Solvent-Free Strecker Reaction

“…In this regard, the unsaturated metal centers (UMCs) that can be either pre-existing or created upon activation, as Lewis acid sites, provided a direction for the development of new catalysts. , The first such example was reported by Fujita and co-workers in the cyanosilylation reaction of benzaldehyde with cyanotrimethylsilane to produce cynohydrins . Inspired by this breakthrough development, there have been various successful attempts for the utilization of MOFs/CPs for the cyanosilylation reaction and other similar reactions, such as Mukaiyama-aldol reaction, Knoevenagel condensation, ring-opening reaction, redox reaction, and carbon dioxide (CO 2 ) fixation. − Moreover, the use of MOFs/CPs as the heterogeneous catalyst in multicomponent reactions to synthesize biologically and pharmacologically essential products is also explored. − …”