Showing papers on "Pyran published in 2019"
TL;DR: The first (3+3)-annulation process of donor-acceptor cyclopropanes using synergistic catalysis is reported, to afford multiply substituted pyran scaffolds in high yield and diastereoselectivity.
Abstract: The first (3+3)-annulation process of donor-acceptor cyclopropanes using synergistic catalysis is reported. The Rh2 (OAc)4 -catalyzed decomposition of diazo carbonyl compounds generated carbonyl ylides in situ. These 1,3-dipoles were converted with donor-acceptor cyclopropanes, activated by Lewis acid catalysis, to afford multiply substituted pyran scaffolds in high yield and diastereoselectivity. Extensive optimization studies enabled access to 9-oxabicyclo[3.3.1]nonan-2-one and 10-oxabicyclo[4.3.1]decen-2-ol cores, exploiting solvent effects on intermediate reactivity.
78 citations
69 citations
49 citations
TL;DR: A D-π-A 4H-pyran derivative (AMP) containing dicyanomethylene, benzene, and 4-hydroxybenzene units was designed and synthesized in this paper.
Abstract: A D-π-A 4H-pyran derivative (AMP) containing dicyanomethylene, benzene, and 4-hydroxybenzene units was designed and synthesized, which exhibited an aggregation-induced emission property. This asymm...
42 citations
TL;DR: A novel approach for visible-light initiated synthesis of 2-amino-4H-pyran-3,5-dicarbonitrile derivatives via one-pot, three-component reaction of aldehydes or isatins, malononitrile and α-cyano ketones has been developed.
Abstract: A novel approach for the visible-light-initiated synthesis of 2-amino-4H-pyran-3,5-dicarbonitrile derivatives via a one-pot, three-component reaction of aldehydes or isatins, malononitrile, and α-cyano ketones has been developed. The reaction was carried out at room temperature in ethanol/water to give the corresponding products with a wide range of functional groups in high yields. This process did not require any additives or chromatographic separation and could be applied for gram-scale synthesis.
35 citations
TL;DR: Over the course of this study, two key methodological advances were made: a cost-effective procedure for ketone α,β-dehydrogenation using allyl-Pd catalysis, and a Pd-catalyzed protocol to convert epoxyketones to 1,3-diketones.
Abstract: We report the first total synthesis of (+)-granatumine A, a limonoid alkaloid with PTP1B inhibitory activity, in ten steps. Over the course of this study, two key methodological advances were made: a cost-effective procedure for ketone α,β-dehydrogenation using allyl-Pd catalysis, and a Pd-catalyzed protocol to convert epoxyketones to 1,3-diketones. The central tetrasubstituted pyridine is formed by a convergent Knoevenagel condensation and carbonyl-selective electrocyclization cascade, which was followed by a direct transformation of a 2H-pyran to a pyridine. These studies have led to the structural revision of two members of this family.
31 citations
TL;DR: In this paper, the effects of KCl and CaCl2 on the evolution of anhydro sugars in reaction intermediates were examined by using levoglucosan pyranose (LGA_Pyran), maltosan and cyclodextrin as model compounds.
30 citations
TL;DR: In this article, a magnetically recoverable Fe3O4@SiO2-BenzIm-Fc[Cl]/NiCl2 nanoparticle was also synthesized using a simple chemical coprecipitation approach.
27 citations
TL;DR: In this article, a magnetically recoverable Fe3O4@SiO2-BenzIm-Fc[Cl]/ZnCl2 nano-particle was synthesized using a simple chemical coprecipitation approach.
Abstract: In this study, a novel magnetically recoverable Fe3O4@SiO2-BenzIm-Fc[Cl]/ZnCl2 nano-particle was synthesized using a simple chemical coprecipitation approach. In the FT-IR spectroscopy of nano-particles, related absorption peaks appeared which confirmed the successful synthesis of nano-catalyst. In the EDX spectrum of the nano-catalyst, the expected elements on their regions appeared. The XRD diffusion patterns of nano-catalysts showed the crystalline dispersions of Fe3O4 magnetic nano-particles. According to the FE-SEM and TEM images, the nano-particles have relative mono-dispersity and the average size of nano-particles is around 35 nm. The catalytic activities of the novel magnetic nano-particle were evaluated in the one-pot three-component synthesis of a wide variety of pyran annulated bis-heterocyclic derivatives (38 compounds) under ultrasonic irradiation. A simple, facial and highly efficient ultrasound-assisted method has been introduced for the synthesis of fused bis-heterocyclic pyran derivatives by one-pot, three-component reactions at room temperature. A series of pyrano[3,2-c]chromene derivatives were synthesized using a novel nano-catalyst via the condensation reaction of different aldehydes, malononitrile and 4-hydroxycoumarin. Kojic acid was also used in the three-component reaction for the synthesis of pyrano[3,2-b]pyran derivatives. The method was successful in the synthesis of various pyrano[2,3-d]pyrimidine derivatives. Additionally, new ultrasound-assisted synthesis protocol was used for the synthesis of novel chromeno[2,3-d]pyrimidine derivatives via three-component condensation of aromatic aldehydes, orcinol and barbituric acid. The new catalytic method exhibits some notable advantages such as short reaction times, operational simplicity, green reaction conditions, high yields and easy work-up and purification steps. In addition, the novel magnetic nano-particle could be easily separated by an external magnet and reused for six times without significant loss of its catalytic activity in the reaction.
26 citations
TL;DR: In this article, a new acidic mesoporous catalyst (FSM-16/AEPC-SO3H) was successfully synthesized and characterized by FT-IR, TGA, XRD, SEM, TEM, EDS and BET techniques.
Abstract: A new acidic mesoporous catalyst (FSM-16/AEPC-SO3H) was successfully synthesized and characterized by FT-IR, TGA, XRD, SEM, TEM, EDS and BET techniques. The FSM-16/AEPC-SO3H showed excellent catalytic activity for the synthesis of 1,8-dioxo-octahydroxanthene and tetrahydrobenzo[b]pyran derivatives. The synthesized catalyst can also be recycled.
25 citations
TL;DR: In this article, the synthesis of pyranoquinolone-3-carbaldehydes, heterocyclic compounds which were constructed by modifying Vilsmeier-Haack reaction was described.
TL;DR: Highly efficient oxidative annulation of alkynes furnished diversely substituted pyran[2,3,4-4- de]chromene-2-one derivatives and related polycycles in moderate to high yield.
Abstract: Highly efficient oxidative annulation of alkynes furnished diversely substituted pyran[2,3,4-de]chromene-2-one derivatives and related polycycles in moderate to high yield. The reaction is catalyze...
TL;DR: In this article, an ionic liquid-based s-triazine-immobilized silica-coated Fe3O4 magnetic nanoparticles were used for one-pot three-component synthesis of 4,8-dihydropyrano[3,2-b]pyran derivatives in excellent yields.
Abstract: We have described a new method to heterogenize s-triazine catalyst by easy preparation of ionic liquid-based s-triazine-immobilized silica-coated Fe3O4 magnetic nanoparticles [Fe3O4@SiO2-s-triazinium chloride]. The structure of the newly prepared nanoparticles was characterized by Fourier transform infrared, X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray method, vibrating sample magnetometery and thermo-gravimetric analysis. These nanoparticles were identified as an efficient catalyst for one-pot three-component synthesis of 4,8-dihydropyrano[3,2-b]pyran derivatives in excellent yields. The catalyst was easily separated by magnetic decantation, and the recovered nanoparticles were reused for four fresh runs without any significant loss of catalytic activity. The synthesized dihydropyrano[3,2-b]pyrans were evaluated for their antioxidant and antifungal activities and found they are relatively active.
TL;DR: In this paper, the multicomponent reaction of 5-hydroxy-2-methyl-4H-pyran-4-one with carbonyl compounds and Meldrum's acid was studied.
Abstract: Herein, we report the studies of the multicomponent reaction of 5-hydroxy-2-methyl-4H-pyran-4-one with carbonyl compounds and Meldrum's acid. General methods for the synthesis of 6-methyl-3,4-dihydropyrano[3,2-b]pyran-2,8-diones, 3-(3-hydroxy-6-methyl-4-oxo-4H-pyran-2-yl)propanoic acid amides and esters, as well as 7-oxo-7H-furo[3,2-b]pyran-3-ylacetic acids were elaborated. An efficient synthesis of spiro-condensed dihydropyranones containing 5-hydroxy-2-methyl-4H-pyran-4-one fragment was developed.
TL;DR: The prepared organic-inorganic magnetic reagent was used as a reusable and new catalyst to promote the synthesis of tetrahydrobenzo[b]pyran and pyrano[2,3-d]pyrimidinone derivatives as important biologically active compounds.
Abstract: Immobilized NaHSO₄ on core/shell phenylene bridged periodic mesoporous organosilica magnetic nanoparticles (Fe₃O₄@Ph-PMO-NaHSO₄) as a new acidic magnetically separable nanocatalyst was successfully prepared in three steps: (i) preparation of Fe₃O₄ nanoparticles by a precipitation method, (ii) synthesis of an organic-inorganic periodic mesoporous organosilica structure with phenyl groups on the surface of Fe₃O₄ magnetic nanoparticles (MNPs) and (iii) finally adsorption of NaHSO₄ on periodic mesoporous organosilica (PMO) network. The prepared organic-inorganic magnetic reagent was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), N₂ adsorption-desorption and energy-dispersive X-ray (EDX) techniques. Finally, it was used as a reusable and new catalyst to promote the synthesis of tetrahydrobenzo[b]pyran and pyrano[2,3-d]pyrimidinone derivatives as important biologically active compounds. Eco-friendly protocol, high yields, short reaction times and easy and quick isolation of the products are the main advantages of this procedure.
TL;DR: The synthesis and the for β-secretase (BACE-1) inhibitory activity of new series of tetrahydrobenzo [b] pyran derivatives are reported and six compounds have shown significant IC50 values at micromolar level.
TL;DR: The DBU promoted domino annulation reaction of 2-aryl-3-nitrochromenes with two molecular 4-(N,N-dimethylamino)-1-phenacylpyridinium bromides in DMF resulted in unprecedented 1-benzoyl-2,4-diaryldibenzo[b,d]furane derivatives in good yields, in which the six-membered pyran ring was readily converted to the fivemembered furan ring as discussed by the authors.
Abstract: The DBU promoted domino annulation reaction of 2-aryl-3-nitrochromenes with two molecular 4-(N,N-dimethylamino)-1-phenacylpyridinium bromides in DMF resulted in unprecedented 1-benzoyl-2,4-diaryldibenzo[b,d]furane derivatives in good yields, in which the six-membered pyran ring was readily converted to the five-membered furan ring. On the other hand, the three-component reaction of ammonium acetate, 2-aryl-3-nitrochromenes and 4-(N,N-dimethylamino)-1-phenacylpyridinium bromides in refluxing ethanol afforded 2,6-diaryl-4-(2-hydroxyphenyl)pyridines in high yields.
01 Jan 2019
TL;DR: In this article, 3,3′-(butane-1,4-diyl)bis(1-methyl-1H-imidazol-3-ium) dichloride (C4(MIm)2]·2Cl) and 3, 3′-(Butane- 1,4)-diyl (bis) hydrogen sulfate (HSO4) were prepared via adequate, solvent-free methods and characterized using FT-IR, 1H NMR, 13C NMR and potentiometric titration techniques.
Abstract: In the present work, 3,3′-(butane-1,4-diyl)bis(1-methyl-1H-imidazol-3-ium) dichloride ([C4(MIm)2]·2Cl) and 3,3′-(butane-1,4-diyl)bis(1-methyl-1H-imidazol-3-ium) hydrogen sulfate ([C4(MIm)2]·2HSO4) were prepared via adequate, solvent-free methods and characterized using FT-IR, 1H NMR, 13C NMR, and potentiometric titration techniques. These reagents were investigated in the synthesis of 5-arylidene (thio)barbituric acids, 2-arylidene malononitriles, 4H-pyrans, and pyrano[2,3-d] pyrimidineones, and their catalytic activities were compared in the promotion of these reactions. Based on the obtained results, we found that [C4(MIm)2]·2Cl showed more catalytic efficiency where a basic or weak acidic media is needed. In contrast, [C4(MIm)2]·2HSO4 is a powerful catalyst in reactions needing acidic catalysts to enhance the reaction rate. Using these reagents, the products were formed under mild and eco-friendly conditions in excellent yields during short reaction times without needing column chromatography for work-up.
Journal Article•
TL;DR: In this article, a new pyran derivatives based on 8-hydroxyquinoline such as 2-Amino-4-phenyl-4H-pyrano [3,2-h] quinoline-3-carbonitrile (QP-H), 2.
Abstract: We have synthesized a new pyran derivatives based on 8-hydroxyquinoline such as 2-Amino-4-phenyl-4H-pyrano [3,2-h] quinoline-3-carbonitrile (QP-H), 2-Amino-4-(4chlorophenyl)-4H-pyrano-[3,2-h] quinoline-3-carbonitrile (QP-Cl), 2-Amino-4-(4methoxyphenyl)-4H-pyrano-[3,2-h]quinoline-3-carbonitrile (QP-OCH3) and 2-Amino-4-(4nitrophenyl)-4H-pyrano[3,2-h]quinoline-3-carbonitrile (QP-NO2). All the synthesized compounds were identified by elemental analysis data, IR, 1H and 13C NMR spectroscopy and were evaluated and screened “in vitro” by the disk diffusion technique against Grampositive and Gram-negative bacterial strains (E. coli (ATCC35218), S. aureus (ATCC29213), V. parahaemolyticus (ATCC17802), and P. aeruginosa (ATCC27853)). The preliminary screening results showed that all the compounds displayed a potential antibacterial activity against all the tested four Gram bacteria. The results revealed that most of the tested compounds have a very good antibacterial activity compared to the standard antibiotic (Penicillin G).
26 Nov 2019
TL;DR: Eleven new tetrahydrobenzo[b]pyran derivatives were synthesized via a three component reaction of different aromatic aldehydes, methyl cyanoacetate and 1,3-cyclohexadione with water as solvent under catalyst-free microwave irradiation, providing a clean access to the desired products by simple workup.
Abstract: Eleven new tetrahydrobenzo[b]pyran derivatives were synthesized via a three component reaction of different aromatic aldehydes, methyl cyanoacetate and 1,3-cyclohexadione, with water as solvent under catalyst-free microwave irradiation. The structures of all the new molecules were well analysed and their structures established by using various spectral techniques (1H NMR, 13C NMR, 15N NMR and HRMS). Various advantages of reported protocol are the ease of preparation, short reaction times (10 min), aqueous solvent and excellent yields (89–98%). Additionally, this method provides a clean access to the desired products by simple workup.
TL;DR: Pyran is fused into the planar donor moiety to enhance the extinction coefficient and reduce the bandgap, thus two acceptors PTTIC and PTBT-R are designed and synthesized as mentioned in this paper.
TL;DR: Studying the molecular mode of action of compound II15 revealed that the novel triketone structure is a proherbicide of its corresponding phenoxyacetic acid auxin herbicide, which has a herbicidal mechanism similar to that of 2,4-D.
Abstract: In order to develop a novel herbicide containing the β-triketone motif, a series of 4-hydroxyl-3-(2-phenoxyacetyl)-pyran-2-one derivatives were designed and synthesized. The bioassay results showed...
TL;DR: The construction of the pyran ring catalyzed by the cooperation of a flavin-dependent monooxygenase,XimD, and a SnoaL-like cyclase, XimE, in the biosynthesis of xiamenmycins is reported, which suggests a synergistic mechanism in which a group of four residues acts cooperatively as the general acid and base.
Abstract: The pyran ring is a very common structural unit of many natural, bioactive molecules that are widely found in plants, bacteria, and fungi. However, the enzymatic processes by which many of these pyran-containing molecules are formed are unclear. Herein, we report the construction of the pyran ring catalyzed by the cooperation of a flavin-dependent monooxygenase, XimD, and a SnoaL-like cyclase, XimE, in the biosynthesis of xiamenmycins. XimD catalyzes the formation of an epoxide intermediate that spontaneously transforms to furan and pyran products (43:1) in vitro. XimE then catalyzes the formation of the pyran ring in a 6-endo configuration from the epoxide to yield a benzopyran, xiamenmycin B. Further, we obtained the crystallographic structure of XimE, with and without product, which suggests a synergistic mechanism in which a group of four residues (Y46–Y90–H102–E136) acts cooperatively as the general acid and base. Subsequent structure-based analysis of possible viable substrates indicates that both X...
TL;DR: In this article, a simple, efficient, eco-friendly and catalyst-free procedure was developed for the construction of novel coumarin-spiro[indoline-3,4'-pyran] conjugates via three-component reactions of various syn...
Abstract: A simple, efficient, eco-friendly and catalyst-free procedure was developed for the construction of novel coumarin-spiro[indoline-3,4'-pyran] conjugates via three-component reactions of various syn...
TL;DR: Fe3O4 as mentioned in this paper is an effective, magnetic and novel heterogeneous reusable nanocatalyst used for synthesis of substituted 2.aminodihydropyrano [3,2]-pyran‐3.cyano in high yields via in situ reaction of azido kojic acid, malononitrile and various aldehydes.
Abstract: (Fe3O4@silica‐MCM‐41@DABCO) as an effective, magnetic and novel heterogeneous reusable nanocatalyst was used for synthesis of substituted 2‐aminodihydropyrano [3,2‐b]pyran‐3‐cyano in high yields via in situ reaction of azido kojic acid, malononitrile and various aldehydes.