75665-89-3Relevant academic research and scientific papers
Preparation method and application of apocynin and derivatives of apocynin
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Paragraph 0059-0062, (2020/01/12)
The invention belongs to the technical field of chemical biology, and particularly relates to a preparation method of apocynin and derivatives of the apocynin and an application of the apocynin and the derivatives of the apocynin in skin care products. The apocynin and the derivatives of the apocynin provided by the invention can promote collagen synthesis, help skin damage repair, and can be usedin the skin care products.
Comparison of a series of laccase mediators in the electro-oxidation reactions of non-phenolic lignin model compounds
Shiraishi, Takumi,Sannami, Yumi,Kamitakahara, Hiroshi,Takano, Toshiyuki
, p. 440 - 446 (2013/10/01)
The electro-oxidations of non-phenolic lignin model compounds in an electrolytic mediator system (EMS) have been investigated with several laccase mediators, including N-hydroxyphthalimide (NHPI), 1-hydroxybenzotriazole (HBT), violuric acid (VLA), 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS), under the same reaction conditions. In the bulk electrolyses of the monomeric model compound [1-(4′-ethoxy-3′-methoxyphenyl)ethanol (1G)], oxidation with NHPI gave the corresponding Cα=O product (2G) in high yield, whereas the oxidations with HBT, VLA, and TEMPO afforded 2G in moderate yields. The highest reaction selectivity for the guaiacylunits was found in the oxidation conducted in the presence of ABTS, although the yield was low. In the bulk electrolyses of the dimeric model compound [4-ethoxy-3-methoxyphenylglycerol- β-guaiacyl ether (3G)], the oxidation with NHPI gave the corresponding Cα=O product (4G) in high yield, whereas the oxidations with HBT, VLA, and TEMPO gave 4G in low yields. In contrast, the oxidation with ABTS gave a Cα-Cβ cleavage product (5G) in 5.5% yield. The selectivity of the mediators in the EMS reaction effectively reflected the mechanisms of their reactions, as reported for the laccase mediator system. NHPI was confirmed to be the best mediator in the present system for the selective Cα-carbonylation of the non-phenolic β-O-4 structures in lignin.
Hydrogenolysis of β-O-4 lignin model dimers by a ruthenium-xantphos catalyst
Wu, Adam,Patrick, Brian O.,Chung, Enoch,James, Brian R.
, p. 11093 - 11106 (2012/10/30)
Hydrogenolysis reactions of so-called lignin model dimers using a Ru-xantphos catalyst are presented (xantphos = 4,5-bis(diphenylphosphino)-9,9- dimethylxanthene). For example, of some nine models studied, the alcohol, 2-(2-methoxyphenoxy)-1-phenylethanol (1), with 5 mol% Ru(H)2(CO) (PPh3)(xantphos) (18) in toluene-d8 at 135 °C for 20 h under N2, gives in ～95% yield the C-O cleavage hydrogenolysis products, acetophenone (14) and guaiacol (17), and a small amount (1H NMR spectroscopy. The in situ Ru(H)2(CO)(PPh 3)3/xantphos system gives similar findings, confirming a recent report (J. M. Nichols et al., J. Am. Chem. Soc., 2010, 132, 12554). The active catalyst is formulated 'for convenience' as 'Ru(CO)(xantphos)'. The hydrogenolysis mechanism proceeds by initial dehydrogenation to give the ketone 4, which then undergoes hydrogenolysis of the C-O bond to give 14 and 17. Hydrogenolysis of 4 to 14 and 17 also occurs using the Ru catalyst under 1 atm H2; in contrast, use of 3-hydroxy-2-(2-methoxyphenoxy)-1-phenyl-1- propanone (7), for example, where the CH2 of 4 has been changed to CHCH2OH, gives a low yield (≤15%) of hydrogenolysis products. Similarly, the diol substrate, 2-(2-methoxyphenoxy)-1-phenyl-1,3-propanediol (9), gives low yields of hydrogenolysis products. These low yields are due to formation of the catalytically inactive complexes Ru(CO)(xantphos)[C(O)C(OC 6H4OMe)C(Ph)O] (20) and/or Ru(CO)(xantphos)[C(O)CHC(Ph)O] (21), where the organic fragments result from dehydrogenation of CH 2OH moieties in 7 and 9. Trace amounts of Ru(CO)(xantphos)(OC 6H4O), a catecholate complex, are isolated from the reaction of 18 with 1. Improved syntheses of 18 and lignin models are also presented.
Acetylation of aromatic ethers using acetic anhydride over solid acid catalysts in a solvent-free system. Scope of the reaction for substituted ethers
Smith, Keith,El-Hiti, Gamal A.,Jayne, Anthony J.,Butters, Michael
, p. 1560 - 1564 (2007/10/03)
The acetylation of aryl ethers using acetic anhydride in the presence of zeolites under modest conditions in a solvent-free system gave the corresponding para-acetylated products in high yields. The zeolite can be recovered, regenerated and reused to give almost the same yields as that given when fresh zeolite is used.
Singlet oxygen in the photodegradation of lignin models
Crestini, Claudia,D'Auria, Maurizio
, p. 7877 - 7888 (2007/10/03)
The photochemical oxidation of lignin models in the presence of singlet oxygen was studied. The treatment of the non-phenolic β-O-4 aryl ether derivatives 6, 7, and 8 in the presence of both oxygen and Rose Bengal gave products deriving from a formal β-C-O cleavage formation. By this way. the derivatives 12, 13, and 15 were obtained. The photochemical oxidation of the phenolic β-O-4 aryl ether 9 gave the same type of product confirming that, in this case, the presence of the carbonyl group is not indispensable to have the cleavage reaction. The use of the model compound 10 showed that, when the phenoxy part of the molecule shows a lower reactivity towards singlet oxygen, the oxidation of the phenol moiety to hydroquinone call occur. The photochemical behaviour of these model compounds can be rationalised from a reaction of singlet oxygen with the phenoxy part of the molecule.
Photophysics and photochemistry of a lignin model molecule containing α-carbonyl guaiacyl and 4-hydroxy-3-methoxybenzyl alcohol moieties
Castellan, Alain,Grelier, Stephane,Kessab, Larbi,Nourmamode, Aziz,Hannachi, Yacine
, p. 1131 - 1138 (2007/10/03)
A lignin model molecule (DCOOH), incorporating an α-carbonyl guaiacyl part and a 4-hydroxy-3-methoxybenzyl alcohol moiety linked by an n-hexane chain, has been synthesized. The electronic absorption spectra in the ground and excited states (flash photolysis) and the luminescence properties in dilute solutions (alcohol and alkane) and in hydroxypropylcellulose (HPC) film were studied at room temperature and at 77 K in comparison with models representing the two ends. They show that in nonpolar and very good hydrogen donor solvents there is interaction between the excited carbonyl and the phenolic group, the chain probably being in a folded conformation. In alcoholic solvents and in HPC films, an intermolecular interaction between the carbonyl chromophore and the hydroxy group of the solvent was observed, the hexamethylene chain being in an extended conformation. UV irradiation of the dimer and the carbonyl monomer, incorporated in an HPC film, show similar reactivity which appears to involve an intermolecular hydrogen abstraction by the excited-state carbonyl group from the surrounding medium. The reactivity of the carbonyl derivatives in isopropyl alcohol and tetrahydrofuran (THF) was found to be similar to that observed for the films. In THF, two isomeric photoadducts between the carbonyl monomer (MCOET) and tetrahydrofuran were isolated and characterized. In alkane solvents, UV irradiation of the dimer leads to the appearance of a new band in the long wavelength range characteristic of the production and oxidation of phenoxyl radicals, which are oxidized to coloured structures such as quinones. The main conclusion of the study is that for the first time, it is shown that in the solid state the carbohydrate matrix does not tend to promote the oxidation process between the carbonyl and the phenol. This result is important for the understanding of the mechanism of photoyellowing of lignin-rich pulps.
Reactions of α,β-Unsaturated Ketones with Nucleophiles
Akhtar, M. Shamim,Seth, M.,Bhaduri, A. P.
, p. 71 - 72 (2007/10/02)
Selective loss of an acetyl group from 4-acetoxy-3-methoxycarbonyl or acetyl-4-substitutedphenylbut-3-ene-2-ones is shown to occur during their reactions with nucleophiles.
An Unambiguous Synthesis of Melannein
Ahluwalia, V. K.,Kapur, Kanchan,Manchanda, Saroj
, p. 186 - 188 (2007/10/02)
Melannein (6-hydroxy-7-methoxy-4-(3'-hydroxy-4'-methoxyphenyl)coumarin, I) and its O,O-diethyl ether (II) have been synthesised.The steps involved in the synthesis of I and II are the respective condensation of o-methoxyhydroquinone with ethyl m-benzyloxy-p-methoxybenzoylacetate (XI) and ethyl m-ethoxy-p-methoxybenzoylacetate (III) in absolute ethyl alcohol in the presence of dry hydrogen chloride gas.The isomeric O,O-diethyl ether of melannein, viz. 6-ethoxy-7-methoxy-4(4'-ethoxy-3'-methoxyphenyl)coumarin (VI) has also been prepared by the condensation of o-methoxyhydroquinone with ethyl p-ethoxy-m-methoxybenzoylacetate (VII).The esters (III), (VII) and (XI) have been prepared by the reaction of the appropriate acetophenone derivatives with diethyl carbonate in the presence of sodium hydride.
