Coumarin-naphthohydrazone ligand with a rare coordination mode to form Mn(II) and Co(II) 1-D coordination polymers: synthesis,characterization, and crystal structure

The hydrazone (E)-3-hydroxy-N’-(1-(2-oxo-2H-chromen-3-yl)ethylidene)-2-naphthohydrazide (H₂L) was synthesized from the reaction of 3-acetylcoumarin and 3-hydroxy-2-naphthoic hydrazide in methanol. Compounds [Mn(H₂L)(NO₃)₂(CH₃OH)]·CH₃OH (1a), [Mn(HL)(NO₃)(CH₃OH)]_n (1b), [Co(HL)(NO₃)(CH₃OH)]_n (2), and [Cu(HL)(NO₃)] (3) were obtained by reaction of an equimolar amount of H₂L with nitrate salts of Mn(II), Co(II), or Cu(II) in methanol. The reaction of ligand and Mn(NO₃)₂·4H₂O was also carried out in the presence of sodium azide which led to the 1-D coordination polymer, [Mn(HL)(N₃)(CH₃OH)]_n (4). All of the synthesized compounds were characterized by elemental analyses and spectroscopic methods. Single-crystal X-ray analysis of 1–4 indicated that H₂L is neutral (in 1a) or mononegative ligand (in 1b, 2, 3 and 4). In 1b, 2 and 4 the 1-D polymeric chain is found by a rare coordination mode of this kind of hydrazone ligand since the naphtholic oxygen is coordinated to the neighboring metal ions while the NH moiety of hydrazone remains intact, also confirmed by FT-IR spectroscopic studies. The thermal stability of 2 and 4 were also studied from 30–1000 °C.     

Synthesis and in-vitro antioxidant activities of some coumarin derivatives containing 1,2,3-triazole ring

A new green protocol was developed for the S-alkylation of 2-mercapto-1,3,4-oxadiazole by the reaction of 5-substituted-2-mercapto-1,3,4-oxadiazole with propargyl bromide in sodium bicarbonate in water. The newly synthesized 5-[(substitutedphenoxy)methyl]-2-[(prop-2-yn-1-yl)sulfanyl]-1,3,4-oxadiazole when reacted with azidomethyl coumarins underwent regioselective reaction yielding 4-(((4-((5-((substitutedphenoxy)methyl)-1,3,4-oxadiazol-2-yl)sulfanylmethyl)-1H-1,2,3-triazol-1-yl)methyl)-6-methyl)-2H-chromene-2-one or 1-((4-((5-((substitutedphenoxy)methyl)-1,3,4-oxadiazol-2-yl)sulfanylmethy)-1H-1,2,3-triazol-1-yl-)methyl)-3H-benzo[f]chromene-3-one. Structures of the newly synthesized compounds were confirmed by spectral and analytical data. The compounds were screened for their in-vitro antioxidant property.     

Multi-targeted directed ligands for Alzheimer’s disease: design of novel lead coumarin conjugates

Alzheimer’s Disease (AD) is a neurodegenerative disease characterized by central nervous system insults with progressive cognitive (memory, attention) and non-cognitive (anxiety, depression) impairments. Pathophysiological events affect predominantly cholinergic neuronal loss and dysfunctions of the dopaminergic system. The aim of the current study was to design multi-targeted directed lead structures based on the coumarin scaffold with inhibitory properties at two key enzymes in disease relevant systems, i.e. acetylcholinesterase (AChE) and monoamine oxidase B (MAO-B). Conventional and microwave synthetic methods were utilized to synthesize coumarin scaffold-based novel morpholino, piperidino, thiophene and erucic acid conjugates. Biological assays indicated that the coumarin–morpholine ether conjugate BPR 10 was the most potent hMAO-B inhibitor. The coumarin–piperidine conjugates BPR 13 and BPR 12 were the most potent inhibitors of eeAChE at 100 μM and 1 μM, respectively. Molecular modelling studies were conducted with Accelrys^® Discovery Studio^® V3.1.1 utilising the published hMAO-B (2V61) and hAChE (4EY7) crystal structures. Compound BPR 10 occupies both the entrance and substrate cavities of the active site of MAO-B. BPR 13 resides in both the peripheral anionic site (PAS) and the catalytic anionic site (CAS) of hAChE. This study demonstrated that the coumarin scaffold serves as a promising pharmacophore for MTDLs design.     

Reversible photodimerization of coumarin derivatives dispersed in poly(vinyl acetate)

Four photoreactive coumarin derivatives were successfully synthesized from 7-hydroxy-coumarin and 7-hydroxy-4-methylcoumarin, i.e., 7-propionyloxy-4-methylcoumarin (M₁), 7-palmitoyloxy-4-methylcoumarin (M₂), 7-propionyloxycoumarin (M₃), and 7-palmitoy-loxycoumarin (M₄). Reversible photodimerization (350 or 300 nm) and photocleavage (254 nm) of these coumarin derivatives dispersed in poly(vinyl acetate) (PVAc) were investigated by tracing their UV absorbance variations at 310 nm. The M₂ and M₄ with long palmitoyl chain show much better photoreaction reversibility than M₁ and M₃ with short propionyl chain. Moreover, photodimerization rate (under 350 nm) of M₂ is greater than 200 times of that of M₁. This has been explained by the formation of suitable conformation for revers-ible photodimerization due to the hydrophobic interactions. Photodimerization of M₂ is ca. 3 times quicker than that of M₄, indicating 4-methyl substitution enhances pho-todimerization. The influence of photodimerization wavelength (350 and 300 nm) and photosensitizer (benzophenone) have also been investigated in detail. © 1995 John Wiley & Sons. Inc.     

DFT and TD‐DFT investigation of IR and UV spectra of solvated molecules: Comparison of two SCRF continuum models

We report the calculation of liquid‐phase infrared (IR) and ultraviolet (UV) spectra in the framework of the solute's response to the reaction field of several solvents. In particular, we compare these two properties for the multipolar expansion model developed in the Nancy continuum model (NCM) and the polarized continuum model (PCM) scheme developed in Pise and Naples. All calculations are carried out at the (TD‐)DFT/6–311G(2d,2p) level of theory. The cavity size used for modeling the solute effects on the IR and UV spectra are examined. To calibrate the solute cavity size, we have investigated the IR spectra of coumarin and of a set of 14 additional solutes of different size and polarity in several dielectrical surroundings. It turns out that: (i) PCM and NCM present an identical behavior when a common cavity is used to calibrate the models; and (ii) for both NCM and PCM models, the IR spectra are highly sensitive to the solute and solvent polarity. The UV/VIS investigation of coumarin derivatives demonstrates that both models provide close estimates of λ_max independent of the solute cavity size. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Reactions of 2(3)-ethoxycarbonyl-5,6,7,8-tetrafluorochromones with methylamine

2-Ethoxycarbonyl-5,6,7,8-tetrafluorochromone reacts with methylamine differently, depending on the solvent nature and the amount of the amine: in DMSO and MeCN, the fluorine atom at the C(7) atom is initially replaced and then the C(2) and/or C(9) are attacked, while in ethanol, the reaction involves the C(2) atom with opening of the pyrone ring. The reaction of 3-ethoxycarbonyl-5,6,7,8-tetrafluoro-2-methylchromone with methylamine results, regardless of the solvent, in opening of the chromone ring and the formation of intermediate ethyl 3-(3,4,5,6-tetrafluoro-2-hydroxyphenyl)-2-(1-methylamino)ethylidene-3-oxopropionate, which undergoes intramolecular cyclization to give 5,6,7,8-tetrafluoro-3-(1-methyl-amino)ethylidene-3,4-dihydro-2H-benzopyran-2,4-dione. Dedicated to Academician N. S. Zefirov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2093–2098, September, 2005.     

香豆素合成工艺的改进

香豆素是一种用途广泛的香料,虽然已有多种合成方法,但国内仍采用以水杨醛为原料的路线(产率为60%左右),提高产率是改进其合成工艺的关键。我们曾以氟化钠代替乙酸钠作催化剂,以水杨醛和乙酐为原料合成了香豆素,提高了产率。本文又采用两     

Photodimerization of Coumarin Functionalized Poly(alkyl Acrylate) and Poly(alkyl Methacrylate) Random Copolymers: Influence of Copolymer Composition on Photocrosslinking

Coumarin‐containing poly(alkyl (meth)acrylates) were prepared via 70–80% esterification of hydroxy‐containing acrylic copolymers, then solution cast into thin films and photocrosslinked via the dimerization of coumarin derivatives with UVA light. The coumarin‐modified polymers crosslinked upon exposure and exhibited gel fractions between 74 and 99%. Coumarin dimerization efficiency increased with higher polymer mobility at the irradiation temperature. The effects of light intensity and irradiation time in photo‐dimerized systems followed the Bunsen‐Roscoe reciprocity law indicating that coumarin photodimerization depended only on dose. Thus, low intensities are overcome with longer times. This is an important advantage over photoinitiated free radical crosslinking which depends on irradiation intensity to the ½ power.     

Palladium-catalyzed cross-coupling reactions of coumarin derivatives: An overview

Coumarins are omnipresent in several plants and exhibit a plethora of pharmacological properties, making them an important scaffold in organic synthesis. Naturally, the chemistry of this motif has attracted ever-increasing attention, among which palladium-catalyzed coupling reactions are the most prevalent one. Numerous useful, easy, and concise syntheses and reactions have been achieved using palladium-catalyzed coupling reactions. This review focuses on recent advances in palladium-catalyzed cross-coupling reactions such as Suzuki, Heck, Stille, Sonogoshira etc. reactions of coumarin derivatives and covers the literature from 2001 to 2020.     

Synthesis of a new coumarin dye for pH independent staining of lysosomes

A novel coumarin analogue, synthesized from 2-formylcinnamic acid and resorcinol via acid catalyzed condensation and intramolecular rearrangement, is used for pH-independent staining of lysosome in live cells via lysosomal esterase mediated fluorogenic deacetylation.