Highly Efficient Polyacrylonitrile Fiber Catalysts Functionalized by Aminopyridines for the Synthesis of 3-Substituted 2-Aminothiophenes in Water

Abstract

Four aminopyridine (AP) functionalized polyacrylonitrile fibers (PANAPFs) were developed. UV–vis, FTIR, EA, and SEM were used to demonstrate the successful preparation of the fiber catalysts. Among the prepared catalysts, the PANp‑AP‑3F (with a C3 chain linker) and PANp‑AP‑6F (with a C6 chain linker) exhibited the best catalytic activity to efficiently catalyze the Gewald reaction of ethyl cyanoacetate and 2,5-dihydroxy-1,4-dithiane in water with yields up to 92% under a low catalyst dosage of 1 mol %. The influences of the position and length of the linker, i.e., the carbon chain between the fiber backbone and the aminopyridine moiety, on the catalytic activities were investigated in detail. In addition, the selected catalyst PANp‑AP‑3F was applied to the Gewald reaction of a series of active nitriles and 2,5-dihydroxy-1,4-dithiane and reused without further treatments. A possible mechanism and a microenvironment promoting process were conceived to explain the excellent catalytic properties of this catalytic system. Furthermore, the PANp‑AP‑3F performed well in a scaled-up experiment indicating its potential application in industry.

Modified polyacrylonitrile fiber as a renewable heterogeneous base catalyst for Henry reaction and Gewald reaction in water

“…The 2‐aminothiophene derivatives are promising compounds in the design of varieties of dyes, conducting polymers, pharmaceuticals, and other compounds . Improving the Gewald reaction of α‐sulfanylaldehydes with active nitriles is an important method to prepare 2‐aminothiophene derivatives . So, we applied the C‐PANF‐Na to the Gewald reaction of 2,5‐dihydroxy‐1,4‐dithiane with ethyl cyanoacetate and the results were listed in the Table .…”

“…In our previous works, PANF has been used as an outstanding organic support for heterogeneous catalysts which have excellent performance in water for Knoevenagel condensation, Friedel–Crafts alkylation, asymmetric Michael addition, nucleophilic addition, and Gewald reaction, and so on . In this work, PANF was crosslinked with hydrazine hydrate and then hydrolyzed by NaOH.…”

“…Many efforts have been made to develop heterogeneous catalysts based on various inorganic materials such as zeolites, metal oxides, mesoporous materials, silicas, and so on. And organic materials like polymers, – cellulose, sporopollenin, starch, and chitosan, and so on.…”

Catalytic Deoxygenative Coupling of Aromatic Esters with Organophosphorus Compounds

“…PdCl2 was obtained from FUJIFILM Wako Pure Chemical Corporation. Phenyl thiophene-2-carboxylate (1A), [1] phenyl thiophene-3-carboxylate (1B), [1] phenyl furan-2-carboxylate (1C), [1] phenyl oxazole-4-carboxylate (1D), [2] phenyl picolinate (1E), [1] phenyl isonicotinate (1F), [1] phenyl pyrazine-2-carboxylate (1H), [1] phenyl isoquinoline-1-carboxylate (1J), [3] phenyl 2-phenylquinoline-4-carboxylate (1L), [1] phenyl 4-methylbenzoate (1M), [4] phenyl 1-naphthoate (1N), [5] phenyl 6-methoxy-2-naphthoate (1O), [5] phenyl anthracene-2-carboxylate (1P), [6] phenyl [1,1'-biphenyl]-2-carboxylate (1Q), [5] phenyl [1,1'-biphenyl]-4-carboxylate (1R), [5] phenyl 4'-(tert-butyl)-[1,1'-biphenyl]-4-carboxylate (1S), [7] phenyl 4-methoxybenzoate (1T), [4] phenyl benzo[d] [1,3]dioxole-5-carboxylate (1U), [5] phenyl 4-(trifluoromethoxy)benzoate (1V), [8] phenyl 4-(trifluoromethyl)benzoate (1W), [4] phenyl 4-cyanobenzoate (1Y), [4] phenyl 3-(dimethylamino)benzoate (1Z), [5] phenyl 4-vinylbenzoate (1AA), [9] phenyl 4-acetylbenzoate (1AB), [10] methyl phenyl terephthalate (1AC), [5] phenyl 4-(N,N-dipropylsulfamoyl)benzoate (1AI), [6] [2] methyl thiophene-2-carboxylate (5A), [11] thiophene-2-carbaldehyde (5B), [12] 4-(trifluoromethyl)phenyl thiophene-2-carboxylate (5C), [13] phenyl thiophene-2-carbothioate (5E), [14] and 2-(phenoxymethyl)thiophene (5F) [15] were synthesized according to procedures and the spectra matched with those of compounds reported in the literature.…”

“…the ligand was changed from dcypt to various phosphine ligands,the highest yield of 3A was obtained (89% yield) without any decarbonylative product 4A (using dcype, Table 1, entries [8][9][10][11][12][13][14][15][16]. It should be noted that the reaction hardly proceeds without the Pd metal or the ligand (Table 1, entries 17 and 18).…”