- Asymmetric Henry reaction catalyzed by a copper tridentate chiral schiff-base complex
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A series of copper-tridentate chiral Schiff-base complexes were prepared and employed in an asymmetric Henry reaction, affording the corresponding adducts in good yields and with high enantioselectivities (up to 96% ee).
- Lai, Guoyin,Wang, Sujing,Wang, Zhiyong
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Read Online
- Synthesis, structure and stability of a chiral imine-based Schiff-based ligand derived from L-glutamic acid and its [Cu4] complex
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Studies of the stability of a ligand derived from L-glutamic acid and ortho-vanillin and its new [Cu4] complex are presented. The [Cu4] complex contains a heterocubane [CuII4O4] core and pendant carboxylic groups increasing its solubility in water, also under basic conditions. The stability of the complex in different solvents is confirmed with ESI-MS studies and such experiments as successful recrystallization. The complex is stable also under physiological conditions whereas the ligand is partly decomposed to L-glutamic acid and ortho-vanillin.
- Muche, Simon,Levacheva, Irina,Samsonova, Olga,Biernasiuk, Anna,Malm, Anna,Lonsdale, Richard,Popio?ek, ?ukasz,Bakowsky, Udo,Ho?yńska, Ma?gorzata
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- ortho-Hydroxylation of Aromatic Aldehydes: A Short Synthesis of 2-Hydroxypyrene-1-carbaldehyde
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A new methodology for the ortho-hydroxylation of aromatic aldehydes via ortho-lithiated aromatic amino alkoxides provides easy access to 2-hydroxypyrene-1-carbaldehyde, a valuable precursor for biologically important pyrenofurans and pyrenocoumarins.
- Einhorn, Jacques,Luche, Jean-Louis,Demerseman, Pierre
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- Molecular modeling and snake venom phospholipase A2 inhibition by phenolic compounds: Structure-activity relationship
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In our earlier study, we have reported that a phenolic compound 2-hydroxy-4-methoxybenzaldehyde from Janakia arayalpatra root extract was active against Viper and Cobra envenomations. Based on the structure of this natural product, libraries of synthetic structurally variant phenolic compounds were studied through molecular docking on the venom protein. To validate the activity of eight selected compounds, we have tested them in in vivo and in vitro models. The compound 21 (2-hydroxy-3-methoxy benzaldehyde), 22 (2-hydroxy-4-methoxybenzaldehyde) and 35 (2-hydroxy-3-methoxybenzylalcohol) were found to be active against venom-induced pathophysiological changes. The compounds 20, 15 and 35 displayed maximum anti-hemorrhagic, anti-lethal and PLA2 inhibitory activity respectively. In terms of SAR, the presence of a formyl group in conjunction with a phenolic group was seen as a significant contributor towards increasing the antivenom activity. The above observations confirmed the anti-venom activity of the phenolic compounds which needs to be further investigated for the development of new anti-snake venom leads.
- Alam, Md. Iqbal,Alam, Mohammed A.,Alam, Ozair,Nargotra, Amit,Taneja, Subhash Chandra,Koul, Surrinder
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- Iron-catalyzed arene C-H hydroxylation
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The sustainable, undirected, and selective catalytic hydroxylation of arenes remains an ongoing research challenge because of the relative inertness of aryl carbon-hydrogen bonds, the higher reactivity of the phenolic products leading to over-oxidized by-products, and the frequently insufficient regioselectivity. We report that iron coordinated by a bioinspired L-cystine-derived ligand can catalyze undirected arene carbon-hydrogen hydroxylation with hydrogen peroxide as the terminal oxidant. The reaction is distinguished by its broad substrate scope, excellent selectivity, and good yields, and it showcases compatibility with oxidation-sensitive functional groups, such as alcohols, polyphenols, aldehydes, and even a boronic acid. This method is well suited for the synthesis of polyphenols through multiple carbon-hydrogen hydroxylations, as well as the late-stage functionalization of natural products and drug molecules.
- Cheng, Lu,Wang, Huihui,Cai, Hengrui,Zhang, Jie,Gong, Xu,Han, Wei
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- Enantioselective Hydroboration of Ketones Catalyzed by Rare-Earth-Metal Complexes Supported with Phenoxy-Functionalized TsDPEN Ligands
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Six novel chiral rare-earth-metal complexes bearing the phenoxy-functionalized TsDPEN ligand H3L1 (H3L1 = N-((1R,2R)-2-((3,5-di-Tert-butyl-2-hydroxybenzyl)amino)-1,2-diphenylethyl)-4-methylbenzenesulfonamide) were synthesized successfully and well characterized. The solid-state structures of four tetranuclear rare-earth-metal complexes [RE2L13]2 (RE = Nd (1), Sm (2), Eu (3), Gd (4)) and the dual-core yttrium complex Y2L13 (5) were determined by X-ray diffraction, respectively. The structure of lanthanum complex 6 was speculated by the 1H DOSY spectroscopy in THF-d8 together with DFT calculations. Complexes 1-5 were employed to catalyze the enantioselective hydroboration of ketones and α,β-unsaturated ketones using pinacolborane (HBpin) as a reductant, and complex 1 gave better outcomes in comparison to the others. The corresponding secondary alcohols were obtained in excellent yields and moderate ee values. The same results were also achieved using the combined catalyst system of the neodymium amide Nd[N(SiMe3)2]3 with the phenoxy-functionalized TsDPEN ligand H3L1 in a 1:1.5 molar ratio.
- Yu, Qishun,Lu, Chengrong,Zhao, Bei
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supporting information
p. 2529 - 2537
(2021/07/28)
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- Phosphine-catalyzed sequential (2+3)/(2+4) annulation of γ-vinyl allenoates: Access to the synthesis of chromeno[4,3-: B] pyrroles
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A phosphine-catalyzed cascade (2+3)/(2+4) cyclization reaction of γ-vinyl allenoates with aldimine esters has been developed to provide a series of chromeno[4,3-b]pyrrole derivatives that contain three contiguous stereogenic centers. The method gives a good yield, excellent chemoselectivity and diastereoselectivity under mild conditions.
- Huang, You,Li, Xiaohu
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supporting information
p. 9934 - 9937
(2021/10/12)
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- Method for preparing aldehyde compounds through photocatalytic oxidation cracking β - hydroxyl compound C-C bond
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The invention provides a method for preparing aldehydes from C-C bonds of beta-hydroxy compounds by photocatalytic oxidative cracking. According to the method, the beta-hydroxy compounds are taken asa substrate, oxygen-containing gas is taken as an oxygen source, and C-C bond cracked products, namely, corresponding aldehydes can be generated under illumination in presence of a catalyst. The conditions are mild, the oxidation efficiency and the product yield are high, and the oxygen-containing gas is taken as the oxygen source under the illumination condition, so that the method is economical,environmentally friendly and green, meets the strategy of sustainable developed energy and has broad application prospect.
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Paragraph 0078-0079
(2020/07/29)
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- Solvent-free, microwave assisted oxidation of alcohols with 4-hydroxypyridinium chlorochromate functionalized silica gel
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4-Hydroxypyridinium chlorochromate functionalized silica gel was found to be an efficient and reusable oxidant for the very fast oxidation of primary and secondary alcohols to the corresponding carbonyl compounds under solventfree conditions and microwave irradiation in excellent yields.
- AHMADI, Sayed Ali,GHALEHBANDI, Shermineh Sadat,GHAZANFARI, Dadkhoda,SHEIKHHOSSEINI, Enayatollah
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p. 283 - 289
(2020/10/06)
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- The invention relates to a catechol is raw material of synthetic small bo hong alkali method (by machine translation)
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The invention relates to a catechol is raw material of synthetic small bo hong alkali method, relates to a method for drug synthesis, in order to catechol as raw materials, with the catechol 2 - methyl chloride selective methylation reaction get O-methoxyphenol, continue to selective hydroformylation reaction to obtain the 2 - hydroxy - 3 - methoxybenzaldehyde; with the catechol 2 - methyl chloride methylene compounds obtained by reaction of pepper link, to continue to work with 2 - chloroethylamine catalytic addition reaction pepper ethylamine; the pepper ethylamine with 2 - hydroxy - 3 - methoxybenzaldehyde in a nickel-based catalyst "one-pot" condensation under the conditions of the hydrogenation reaction, the reaction product is hydrochloric acid, cooling of the crystal, and filtering to obtain the hydrochloride condensate; will be hydrochloride compression compound refined, continue to work with the glyoxal, under the condition of a copper-based catalyst, a cyclization reaction is carried out, the reaction product after passing through the refining process, hydrochloric acid, cooling crystallization, filtration washing to obtain the product of the ABS red alkali. The industrialization of this invention fully synthetic production of the ABS red alkali, to create a small bo hong alkali drug chemical synthesis method. (by machine translation)
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- Phosphine-Catalyzed [3+2] Annulation of β-Sulfonamido-Substituted Enones with Sulfamate-Derived Cyclic Imines
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Phosphine-catalyzed [3+2] annulation of β-sulfonamido-substituted enones and sulfamate-derived cyclic imines has been developed, giving a series of imidazoline derivatives in moderate to excellent yields with good to excellent diastereoselectivities. A scale-up reaction worked well under mild reaction conditions. A possible mechanism was proposed on the basis of the results obtained.
- Shi, Wangyu,Zhou, Leijie,Mao, Biming,Wang, Qijun,Wang, Chang,Zhang, Cheng,Li, Xuefeng,Xiao, Yumei,Guo, Hongchao
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supporting information
p. 679 - 685
(2019/01/24)
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- Method for total synthesis of berberine with guaiacol as raw material
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The invention discloses a method for total synthesis of berberine with guaiacol as a raw material. According to a drug synthesis method, guaiacol serves as the raw material, 2-hydroxy-3-methoxybenzaldehyde is obtained through a selective formylation reaction, 2,3-dimethoxybenzaldehyde is obtained through a methylation reaction, pentamethyleneamine is obtained through a methylenenation reaction with catechol as a raw material, and homopiperony lamine is obtained through a one-step catalytic addition reaction; 2,3-dimethoxybenzaldehyde and homopiperony lamine are subjected to a one-pot condensation hydrogenation reaction under the condition of a nickel-based catalyst, hydrochloric acid is added to a reaction product, a crystal substance is cooled, after the reaction product is refined, hydrochloric acid is added, and cooling crystallization and filtration washing are conducted to obtain the product berberine. According to the method, the technology is simplified, and the use of toxic cyanide is avoided; 2,3-dimethoxybenzaldehyde and homopiperony lamine are subjected to a one-pot condensation hydrogenation and salifying technology, the time is saved, the energy is saved, and the costis lowered; in the technological process, solvents are recycled.
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Paragraph 0015
(2019/04/26)
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- Method for in situ preparing o-vanillin by taking pyrocatechol as raw material
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A method for in situ preparing o-vanillin by taking pyrocatechol as the raw material and relates to production methods of drug materials. The method comprises, firstly, taking the pyrocatechol with apurity degree of 99 w% as the raw material; secondly, taking absolute ethyl alcohol as solvent and polyethylene glycol and sodium hydroxide as catalysts; thirdly, taking acetonitrile as solvent, triethylamine as acid-binding agent and magnesium chloride as catalysts; fourthly, adding sodium chloride into reaction liquid, performing chromatographic layering, and removing a water layer; fifthly, cooling raffinate down to -10 DEG C for freezing concentration, and performing rotary evaporation and separation to obtain oily 2-hydroxy-3-methoxybenaldehyde. The raw material applied is a bulk organicraw material of the pyrocatechol, which is easy to acquire and low in price; by means of the technical processes of methylation and then formylation, the method for in situ preparing the o-vanillin bytaking the pyrocatechol as the raw material can shorten the technical process and reduce the cost, thereby being applicable to industrial production of the o-vanillin, overcoming the limitation of yield of the o-vanillin and achieving significant economic and social benefits.
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Paragraph 0013; 0016-0018
(2019/05/02)
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- The invention relates to a raw material for the preparation of the ABS guaiacol red alkali method (by machine translation)
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The invention relates to a raw material for the preparation of the ABS guaiacol red alkali method, relates to a pharmaceutical preparation method, the present invention in order to guaiacol as raw materials, through the selective hydroformylation reaction to obtain the 2 - hydroxy - 3 - methoxybenzaldehyde; to catechol as raw materials, the reaction methylene compounds pepper link, catalytic addition a footwork of to the pepper ethylamine; 2 - hydroxy - 3 - methoxy benzaldehyde with pepper ethylamine in a nickel-based catalyst "one-pot" condensation under the conditions of the hydrogenation reaction, the reaction product is hydrochloric acid, cooling of the crystal, the hydrochloride compression compound crystal refined, continue to work with the glyoxal, under the condition of a copper-based catalyst, a cyclization reaction is carried out, the reaction product after passing through the refining process, hydrochloric acid, cooling crystallization, filtration washing to obtain the product of the ABS red alkali. The invention catechol as raw materials, the reaction process for preparing methylene compounds after the pepper link, one-step catalytic addition reaction pepper ethylamine, shorten the technological process, overcomes the use of toxic cyanide, process green; process solvent recycling. (by machine translation)
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Paragraph 0016
(2019/05/15)
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- Co-immobilization of Laccase and TEMPO in the Compartments of Mesoporous Silica for a Green and One-Pot Cascade Synthesis of Coumarins by Knoevenagel Condensation
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Co-immobilization of bio- and chemocatalysts produces sustainable, recyclable hybrid systems that open new horizons for green cascade approaches in organic synthesis. Here, the co-immobilization of laccase and 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) in mesoporous silica was used for the one-pot aqueous synthesis of 30 coumarin-3-carboxylate derivatives under mild conditions through the condensation of in situ oxidized 2-hydroxybenzyl alcohols and malonate derivatives. A maximum yield was obtained after incubating at pH 6.0 and 45 °C for 24 h. An efficient organic synthesis was catalyzed by the hybrid catalyst in 10 % organic solvent. More than 95 % of the initial activity of the enzyme was preserved after 10 cycles, and no significant catalyst deactivation occurred after 10 runs. This new system efficiently catalyzed the in situ aerobic oxidation of salicyl alcohols, followed by Knoevenagel condensation, which confirmed the possibility of producing efficient hybrid catalysts by co-immobilization of catalytic species in mesoporous materials.
- Mogharabi-Manzari, Mehdi,Amini, Mohsen,Abdollahi, Mohammad,Khoobi, Mehdi,Bagherzadeh, Ghodsieh,Faramarzi, Mohammad Ali
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p. 1542 - 1546
(2018/02/28)
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- Enantioselective Construction of Tetrahydroquinazoline Motifs via Palladium-Catalyzed [4 + 2] Cycloaddition of Vinyl Benzoxazinones with Sulfamate-Derived Cyclic Imines
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A palladium-catalyzed enantioselective [4 + 2] cycloaddition reaction of vinyl benzoxazinones with sulfamate-derived cyclic imines is described, affording the tetrahydroquinazolines bearing several functional rings in high yields (up to 99% yield) with good to excellent diastereoselectivities and excellent enantioselectivities (up to 96% ee). This reaction represents the first Pd-catalyzed asymmetric decarboxylative cycloaddition of vinyl benzoxazinones with imines.
- Wang, Chang,Li, Yan,Wu, Yang,Wang, Qijun,Shi, Wangyu,Yuan, Chunhao,Zhou, Leijie,Xiao, Yumei,Guo, Hongchao
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supporting information
p. 2880 - 2883
(2018/05/29)
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- Synthesis of chiral salalen ligands and their in-situ generated Cu-complexes for asymmetric Henry reaction
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Chiral salalen ligands derived from (S)-proline and derivatives of salicyaldehydes were synthesized, and their in-situ generated Cu (II) complexes were evaluated in the asymmetric Henry reaction. Salalen ligand of different substituents on the phenyl moiety showed remarkable effect on the enantioselectivity of nitro-aldol product of 4-nitrobenzaldehyde and nitromethane. Cu (II) complex generated in situ with (S)-2-(tert-butyl)-6-((2-(((2-hydroxy-3-methylbenzylidene)amino)methyl)pyrrolidin-1-yl)methyl) phenol (10?mol%) and Cu (OAc)2.H2O (10?mol%), found to be better catalyst for nitro-aldol reaction between 4-nitrobenzaldehyde and nitromethane, gave corresponding product in 85% yield and 88% enantiomeric excess (ee) in isopropanol at 35°C after 40?hours. The catalyst also used for the Henry reaction with different substituted benzaldehydes and corresponding products were obtained in 22% to 99% yields with 66% to 92% ee. Henry reaction of 4-nitrobenzaldehyde and prochiral nitroethane gave anti-selective product (dr?=?79/21; anti/syn) in a 91% yield with 80% ee.
- Dixit, Ashish,Kumar, Pramod,Singh, Surendra
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p. 1257 - 1268
(2018/09/25)
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- Synthesis and characterization of lanthanide complexes prepared with 2-((E)-(1-hydroxy-2-methylpropan-2-ylimino)methyl)-6-methoxyphenol
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Rare-earth complexes of the general formula [Ln(H2L1)2(NO3)3] [Ln?=?Gd (1), Ho (2) or Nd (3)] were prepared from an o-vanillin derived Schiff base ligand, 2-((E)-(1-hydroxy-2-methylpropan-2-ylimino)methyl)-6-methoxyphenol (H2L1). The single-crystal X-ray diffraction studies and SHAPE analyses of the Gd(III) and Ho(III) complexes show that the complexes are ten-coordinate and exhibit distorted tetradecahedron geometries. The phenolate oxygen-bridged dinuclear complex, [Ce2(H2L1)(ovan)3(NO3)3] (4, ovan?=?monodeprotonated o-vanillin), was obtained from the reaction of Ce(NO3)3?6H2O with H2L1. X-ray analysis revealed that hydrolysis of H2L1 occurred to yield o-vanillin, which bridged two cerium atoms with the Ce?Ce distance equal to 3.8232(6) ?. The Ce(III) ions are both ten-coordinate, but have different coordination environments, showing tetradecahedron and staggered dodecahedron geometries, respectively. With proton migration occurring from the phenol group to the imine function, complexation of the lanthanides to the ligand gives the Schiff base a zwitterionic phenoxo-iminium form.
- Abrahams, Abubak'r,Madanhire, Tatenda,Hosten, Eric,Betz, Richard
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p. 1994 - 2014
(2017/06/27)
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- Phosphine-Catalyzed [4 + 2] Annulation of Allenoate with Sulfamate-Derived Cyclic Imines: A Reaction Mode Involving γ′-Carbon of α-Substituted Allenoate
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A phosphine-catalyzed [4 + 2] cycloaddition of cyclic α-substituted allenoates with sulfamate-derived cyclic imines has been reported. Using dibenzylphenylphosphine as the nucleophilic catalyst, the reaction worked efficiently to yield various fused multicyclic heterocyclic compounds in high yields with excellent diastereoselectivities. It undergoes a new reaction mode involving γ′-carbon of α-substituted allenoate.
- Mao, Biming,Shi, Wangyu,Liao, Jianning,Liu, Honglei,Zhang, Cheng,Guo, Hongchao
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supporting information
p. 6340 - 6343
(2017/12/08)
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- SMALL MOLECULE INHIBITORS OF TLR2 SIGNALING
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The present invention is drawn to therapeutics and methods of inhibiting signaling by TLR2. The invention provides a method of treating an inflammatory disease or condition in a subject comprising administering to the subject a therapeutically effective amount of a compound of the invention or salt, solvate, hydrate, prodrug, metabolite, or combination thereof.
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Page/Page column 31
(2016/12/12)
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- Zeolites as Shape-Selective Catalysts: Highly Selective Synthesis of Vanillin from Reimer-Tiemann Reaction of Guaiacol and Chloroform
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Reimer-Tiemann reaction of guaiacol and chloroform was carried out in the presence of various zeolites. Vanillin was afforded as major product in a high selectivity. Zeolites played an important role of shape-selective catalysts in the reactions. Among the examined zeolites, ZSM-5 showed the best result to give the desired product vanillin in 85 % selectivity and 58 % yield. Graphical Abstract: [Figure not available: see fulltext.]
- Ren, Shenyong,Wu, Zhenhua,Guo, Qiaoxia,Shen, Baojian
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p. 712 - 714
(2015/08/04)
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- Synthesis of salicylaldehydes from phenols via copper-mediated duff reaction
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A copper-mediated Duff reaction for ortho-selective formylation of phenols has been developed. In the presence of copper species, significant improvements of yield and ortho-selectivity of the Duff formylation were achieved, which provides an easy access to salicylaldehydes from phenols.
- Fu, Xue-Wen,Pu, Wen-Chen,Zhang, Guo-Lin,Wang, Chun
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p. 8147 - 8158
(2015/02/19)
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- Insertion of arynes into the carbon-oxygen double bond of amides and its application into the sequential reactions
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The reaction of arynes, generated from ortho-(trimethylsilyl)aryl triflates, with the CO bond of formamides gave salicylaldehyde derivatives via the formation of formal [2+2] adducts. The sequential transformation of arynes into ortho-disubstituted arenes, o-aminoalkylphenols or o-hydroxyalkylphenols, was achieved by one-pot procedure using dialkylzincs.
- Yoshioka, Eito,Miyabe, Hideto
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experimental part
p. 179 - 189
(2012/02/15)
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- A facile demethylation of ortho substituted aryl methyl ethers promoted by AlCl3
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An efficient and practical demethylation of ortho substituted aryl methyl ethers using AlCl3 has been developed. This method gives a high conversion, is simple to operate and is cost-effective. A mechanism involving the complexation of AlCl3 with the OMe and the adjacent electron withdrawing group is proposed. Many functional groups can be tolerated in the demethylation process, and 29 examples gave a demethylated product in a yield of 90-98%.
- Du, Zhen-Ting,Lu, Jing,Yu, Hong-Rui,Xu, Yan,Li, An-Pai
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experimental part
p. 222 - 227
(2010/08/04)
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- The development of benzimidazoles as selective rho kinase inhibitors
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Rho Kinase (ROCK) is a serine/threonine kinase whose inhibition could prove beneficial in numerous therapeutic areas. We have developed a promising class of ATP-competitive inhibitors based upon a benzimidazole scaffold, which show excellent potency toward ROCK (IC50 10 nM). This report details the optimization of selectivity for ROCK over other related kinases such as Protein kinase A (PKA).
- Sessions, E. Hampton,Smolinski, Michael,Wang, Bo,Frackowiak, Bozena,Chowdhury, Sarwat,Yin, Yan,Chen, Yen Ting,Ruiz, Claudia,Lin, Li,Pocas, Jennifer,Schr?ter, Thomas,Cameron, Michael D.,LoGrasso, Philip,Feng, Yangbo,Bannister, Thomas D.
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scheme or table
p. 1939 - 1943
(2010/09/03)
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- Selective demethylation and debenzylation of aryl ethers by magnesium iodide under solvent-free conditions and its application to the total synthesis of natural products
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An efficient selective demethylation and debenzylation method for aryl methyl/benzyl ethers using magnesium iodide under solvent-free conditions has been developed and applied to the synthesis of natural flavone and biphenyl glycosides. A variety of functional groups including glycoside were tolerated under the reaction conditions. Experimental results indicated that the removal of an O-benzyl group was easier than that of an O-methyl group, regardless of wherever they were meta or para to the carbonyl. Thus selective debenzylation can be achieved for substrates bearing both benzyloxy and methoxy groups.
- Bao, Kai,Fan, Aixue,Dai, Yi,Zhang, Liang,Zhang, Weige,Cheng, Maosheng,Yao, Xinsheng
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scheme or table
p. 5084 - 5090
(2010/04/03)
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- Method for producing optically active salicylaldimine copper complex
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There is provided a method for producing an optically active salicylaldimine copper complex, which method is characterized in that an optically active amino alcohol compound represented by the following formula (1) is reacted with copper hydroxide (II) in an organic solvent. wherein R1 and R2 which are the same or different, each represent lower alkyl groups and the like which may be substituted, X1 and X2 which are the same or different, each represent a hydrogen atom, lower alkyl groups and the like, and the symbol * designates an asymmetric carbon atom.
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- Does the DABCO-catalysed reaction of 2-hydroxybenzaldehydes with methyl acrylate follow a Baylis-Hillman pathway?
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Evidence is presented which supports the intermediacy of dipolar Baylis-Hillman-type adducts in the synthesis of coumarin and chromene derivatives from the reaction of 2-hydroxybenzaldehydes with methyl acrylate in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO).
- Kaye, Perry T.,Musa, Musiliyu A.,Nocanda, Xolani W.,Robinson, Ross S.
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p. 1133 - 1138
(2007/10/03)
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- Selective regeneration of carbonyl compounds from aldoximes and ketoximes, catalyzed by FeCl3 and SeO2
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An oxidative deblocking procedure of aldoximes using FeCl3 and ketoximes using SeO2 in aprotic solvent is reported. Reaction yields are competitive as compared to previous methods. Reactions are easy to work and conditions are mild. Some important features of FeCl3 are mentioned.
- Hangarge,Mane,Chavan,Shingare
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p. 1302 - 1304
(2007/10/03)
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- Flash vacuum pyrolysis of methoxy-substituted lignin model compounds
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The flash vacuum pyrolysis (FVP) of methoxy-substituted fi-O-4 lignin model compounds has been studied at 500 °C to provide mechanistic insight into the primary reaction pathways that occur under conditions of fast pyrolysis. FVP of PhCH2CH2OPh (PPE), a model of the dominant β-O-4 linkage in lignin, proceeds by C-O and C-C cleavage, in a 37:1 ratio, to produce styrene plus phenol as the dominant products and minor amounts of toluene, bibenzyl, and benzaldehyde. From the deuterium isotope effect in the FVP of PhCD2CH2OPh, it was shown that C-O cleavage occurs by homolysis and by 1,2- elimination in a ratio of 1.4:1, respectively. Methoxy substituents enhance the homolysis of the β-O-4 linkage, relative to PPE, in o-CH3O- C6H4OCH2CH2Ph (o-CH3O-PPE) and (o-CH3O)2-C6H3OCH2CH2Ph ((o- CH3O)2-PPE) by a factor of 7.4 and 21, respectively. The methoxy- substituted phenoxy radicals undergo a complex series of reactions, which are dominated by 1,5-, 1,6-, and 1,4-intramolecular hydrogen abstraction, rearrangement, and α-scission reactions. In the FVP of o-CH3O-PPE, the dominant product, salicylaldehyde, forms from the methoxyphenoxy radical by a 1,5-hydrogen shift to form 2-hydroxyphenoxymethyl radical, 1,2-phenyl shift, and β-scission of a hydrogen atom. The 2-hydroxyphenoxymethyl radical can also cleave to form formaldehyde and phenol in which the ratio of 1,2-phenyl shift to β-scission is ca. 4:1. In the FVP of o-CH3O-PPE and (o-CH3O)2- PPE, products (ca. 20 mol %) are also formed by C-O homolysis of the methoxy group. The resulting phenoxy radicals undergo 1,5- and 1,6-hydrogen shifts in a ratio of ca. 2:1 to the aliphatic or benzylic carbon, respectively, of the phenethyl chain. In the FVP of (o-CH3O)2-PPE, o-cresol was the dominant product. It was formed by decomposition of 2-hydroxy-3- hydroxymethylbenzaldehyde and 2-hydroxybenzyl alcohol, which are formed from a complex series of reactions from the 2,6-dimethoxyphenoxy radical. The key step in this reaction sequence was the rapid 1,5-hydrogen shift from 2- hydroxy-3-methoxybenzyloxy radical to 2-hydroxymethyl-6-methoxyphenoxy radical before β-scission of a hydrogen atom to give the substituted benzaldehyde. The 2-hydroxybenzyl alcohols rapidly decompose under the reaction conditions to o-benzoquinone methide and pick up hydrogen from the reactor walls to form o-cresol.
- Britt, Phillip F.,Buchanan III,Cooney, Mark J.,Martineau, Dan R.
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p. 1376 - 1389
(2007/10/03)
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- A mild and chemoselective dealkylation of alkyl aryl ethers by cerium(III) chloride-NaI
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The alkoxy groups present ortho to carbonyl group in alkoxybenzaldehydes are selectively deprotected in high yields leaving other alkoxy groups unaffected by cerium(III) chloride-NaI in refluxing acetonitrile under neutral reaction conditions.
- Yadav,Subba Reddy,Madan,Riaz Hashim
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p. 738 - 739
(2007/10/03)
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- Reimer-Tiemann reactions of guaiacol and catechol in the presence of β-cyclodextrin
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Fairly high selectivities with respect to para-product are achieved when guaiacol and catechol are subjected to Reimer-Tiemann reaction in the presence of β-cyclodextrin (BCD).Although the presence of BCD does not enhance the total aldehyde production, it reduces the proportion of other isomeric aldehydes formed in favour of the para-product.Thus the reaction in the presence of BCD yields 32percent more vanillin in the case of guaiacol and 25percent more protocatechuic aldehyde in the case of catechol in comparison to the one in the absence of BCD.
- Divakar, S.,Maheswaran, M. M.,Narayan, M. S.
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p. 543 - 546
(2007/10/02)
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- REACTION OF MERCAPTOACETIC ACID AND CHLOROACETYL CHLORIDE WITH BENZALAMINO THIAZOLYL COUMARINS
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2-Aryl-3--4-thiazolidinones (III), have been synthesized by the reaction of Schiff's bases (II) derived from 3-(2-amino-4-thiazolyl)-2H-1-benzopyran-2-ones (I) with mercaptoacetic acid.The Schiff's bases on reaction with chloroacetyl chloride in the presence of triethylamine in dioxane gave chloroacetamido derivative (IV) instead of expected compound V.
- Veerabhadraiah, Udarapu,Rajeswar Rao, Vedeela,Padmanabha Rao, Tadepalcy Venkata
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p. 535 - 539
(2007/10/02)
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- Dealkylation of Activated Alkyl Aryl Ethers Using Lithium Chloride in Dimethylformamide
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Alkyl aryl ethers having electron-withdrawing substituents in the ortho or para positions are esily cleaved with lithium chloride in dimethylformamide.
- Bernard, Angela M.,Ghiani, M. Rossella,Piras, Pier Paolo,Rivoldini, Antonio
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p. 287 - 289
(2007/10/02)
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- THE DEALKYLATION OF ORTHO-ALKOXY AROMATIC KETONES AND ALDEHYDES
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A new one-pot protection and subsequent dealkylation of certain alkoxyaromatic carbonyl compounds is described.
- Gillies, Bylain,Loft, Michael S.
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p. 191 - 196
(2007/10/02)
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- Regioselective Mono-O-alkylation of some Pyrocatechoxide Dianions
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In dimethyl sulphoxide the dianions derived from 2,3- or 3,4-dihydroxybenzaldehydes and 4-methylesculetin afford products corresponding to alkylation at the less acidic site while the monoanions give the isomeric phenols.
- Kessar, Satinder V.,Gupta, Yash P.,Mohammad, Taj,Goyal, Manju,Sawal, Kewal K.
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p. 400 - 401
(2007/10/02)
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- Process of preparing hexahydropyrimidines
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This invention relates to hexahydropyrimidines (HHP) of the formula STR1 where R' is a substituted group and R is hydrogen or a substituted group; the process of preparing and the uses therefor, particularly as deterioration inhibitors in hydrocarbon fuels.
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