First Report About the Use of Micellar Keggin Heteropolyacids as Catalysts in the Green Multicomponent Synthesis of Nifedipine Derivatives

Abstract

Micellar Keggin heteropolyacid catalysts were prepared using hexadecyltrimethylammonium bromide (cetyltrimethylammonium bromide-CTAB), 1-hexadecylpyridinium chloride, and Keggin heteropolyacids H 3 PMo 12 O 40 and H 4 PMo 11 VO 40 as precursors. Four catalysts were prepared (PMo12C16, PMo11VC16, PMo12C 16Py, and PMo11VC16Py) and characterized by 31 P NMR, FT-IR, XRD, SEM analysis and textural properties (S BET ). The acidic characteristics of the catalysts were determined by potentiometric titration with n-butylamine. A series of bioactive 1,4-dihydropyridine derivatives such as nifedipine and nemadipine B were synthesized using these new materials, in a one-pot procedure in ethanol. This methodology requires a reaction time of 8 h, and a temperature of 78°C to obtain good to excellent yields of 1,4-dihydropyridine derivatives. The micellar Keggin catalysts are insoluble in polar media, which allows easy removal of the reaction products without affecting their catalytic activity. The leaching test showed that they have an excellent stability and can be used five times as heterogeneous catalysts without appreciable loss of the catalytic activity. Using the same material, unsymmetrical 1,4-dihydropyridines such as nitrendipine can be obtained through a sequence of steps in very good yield (78 %). Graphical Abstract

Mechanochemical enzymatic synthesis of 1,4‐dihydropyridine calcium antagonists and derivatives

“…Among them, 1,4‐DHP calcium antagonists such as felodipine, nifedipine and nitrendipine are recommended for the first line treatment of hypertension . Traditional syntheses of 1,4‐DHP calcium antagonists employ microwave irradiation, visible light or micellar Keggin heteropolyacids as catalysts . However, long reaction times, numerous experimental procedures and/or tedious procedures of catalyst preparation are drawbacks of these methods.…”

Vanadium-doped sodium phosphomolybdate salts as catalysts in the terpene alcohols oxidation with hydrogen peroxide

“…Indeed, Romanelli et al described that the formation of the peroxidemetal intermediate between the peroxide and the HPA catalyst (i.e., Mo or W addenda atoms) is more favorable in the presence of vanadium atom. 87,88 This benecial effect was ascribed to the reduction of the energy gap between HOMO and LUMO orbitals, provoked by the presence of one vanadium atom, which favors the reducibility of Keggin anions, as demonstrated in studies of molecular orbital performed with vanadium-doped phosphomolybdic acids. 89 It is important to highlight that even in the absence of vanadium, the reaction efficiently proceeded; indeed, it was more visible when a strong Brønsted acidity strength was present, which is translated into better catalytic performance, as in the case of H 3 PMo 12 O 40 -catalyzed reaction.…”

Nickel salt of phosphomolybdic acid as a bi-functional homogeneous recyclable catalyst for base free transformation of aldehyde into ester

“…[10][11][12][13][14][15][16] In particular, the use of HPAs and their related compounds as green catalysts is a eld of increasing worldwide importance and numerous studies have been carried out in basic and applied research in the last four decades. [17][18][19][20][21][22] For example, heteropoly acid-based ionic liquids (HPAILs) as novel functionalized ionic liquids have attracted increasing attention, 23,24 and have been reported as efficient and recyclable catalysts for lipophilic alkene epoxidation and alcohol selective oxidation with aqueous H 2 O 2 . [25][26][27][28] Recently, the development of multicomponent reactions (MCRs) and their applications for one-pot production of several important compounds has fostered the synthetic toolbox expansion.…”

“…[41][42][43][44][45][46] It is well known that HPAs possess a very strong acidity in form of protons, which can be changed by varying the chemical composition of the primary structure of the heteropolyanion. 17 These exchangeable protons can be easily replaced by other cations, without affecting primary structure. 47,48 Depending on the nature of cations (i.e.…”