- Kinetic ( 18 O and 14 C) and Magnetic ( 13 C) Isotope Effects in the Photo-Fries Rearrangement of 4-Methoxyphenyl Acetate
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Kinetic isotope effects (KIE) were measured for the photorearrangement of 4-methoxyphenyl acetate (1) into 2-acetyl-4-methoxyphenol (2) in ethanol solution.The KIE for labeling the phenolic oxygen atom with 18 O was 1.0000+/-0.0023.The KIE for labeling with 14 C at the α-carbon atom of the acetyl group was measured in two ways: with recovered 1 (0.9988+/-0.0051) and with isolated 2 (1.007+/-0.008).Labeling with 13 C at the α-carbon atom led to a magnetic, inverse isotope effect (0.9511+/-0.0042).The results show that there is not a detectable activation barrier for breaking the ester bond and that 2 is formed by recombination of a caged radical pair which originates from an excited singlet state.Surprisingly, labeling of 1 with 14 C in the ortho position led to a KIE, measured with recovered 1, of 1.0286+/-0.0021.We attribute this to a reaction of 1, as yet unknown, which is not associated with rearrangement into 2.It is noteworthy that rearrangement is not the major reaction pathway.The larger part (over 60percent) of 1 is converted into polymeric material.The origin of the polymeric material lay in the scission product, 4-methoxyphenol (3), which was itself not obtained during the lengthy irradiations of the KIE work.Whether the KIE for ortho labeling is connected with polymer formation is not now known.
- Shine, Henry J.,Subotkowski, Witold
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Read Online
- Anchimerically Assisted Selective Cleavage of Acid-Labile Aryl Alkyl Ethers by Aluminum Triiodide and N, N-Dimethylformamide Dimethyl Acetal
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Aluminum triiodide is harnessed by N,N-dimethylformamide dimethyl acetal (DMF-DMA) for the selective cleavage of ethers via neighboring group participation. Various acid-labile functional groups, including carboxylate, allyl, tert-butyldimethylsilyl (TBS), and tert-butoxycarbonyl (Boc), suffer the conditions intact. The method offers an efficient approach to cleaving catechol monoalkyl ethers and to uncovering phenols from acetal-type protecting groups such as methoxymethyl (MOM), methoxyethoxymethyl (MEM), and tetrahydropyranyl (THP) chemoselectively.
- Sang, Dayong,Yue, Huaxin,Zhao, Zhengdong,Yang, Pengtao,Tian, Juan
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p. 6429 - 6440
(2020/07/14)
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- Selective ether bond breaking method of aryl alkyl ether
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The invention discloses a selective aryl alkyl ether cracking method, which comprises that aryl alkyl ether, aluminum iodide and an additive are subjected to a selective ether bond cleavage reaction in an organic solvent at a temperature of -20 DEG C to a reflux temperature to generate phenol and derivatives thereof. The method is mild in condition and simple and convenient to operate, is suitablefor cracking aryl alkyl ether containing o-hydroxyl and o-carbonyl and acetal ether, and can also be used for removing tertiary carbon hydroxyl protecting groups with higher steric hindrance, such astriphenylmethyl, tertiary butyl and the like.
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Paragraph 0176-0180
(2020/09/16)
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- Novel p-functionalized chromen-4-on-3-yl chalcones bearing astonishing boronic acid moiety as MDM2 inhibitor: Synthesis, cytotoxic evaluation and simulation studies
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Background: Novel 4-[3-(6/7/8-Substituted 4-Oxo-4H-chromen-3-yl)acryloyl]phenyl-boronic acid derivatives (5a-h) as well as other 6/7/8-substituted-3-(3-oxo-3-(4-substituted-phenyl)prop-1-enyl)-4H-chromen-4-one derivatives (3a-u) have been designed as p53-MDM2 pathway inhibitors and reported to possess significant cytotoxic properties against several cancer cell lines. Objectives: The current project aims to frame the structure-anticancer activity relationship of chromen-4-on-3-yl chalcones (3a-u/5a-h). In addition, docking studies were performed on these chromeno-chalcones in order to have an insight into their interaction possibilities with MDM2 pro-tein. Methods: Twenty-nine chromen-4-on-3-yl chalcone derivatives (3a-u/5a-h) were prepared by utilizing silica supported-HClO4 (green route with magnificent yield) and tested against four cancer cell lines (HCT116, MCF-7, THP-1, NCIH322). Results: Among the series 3a-u, compound 3b exhibited the highest anticancer activity (with IC50 values ranging from 8.6 to 28.4 μM) overall against tested cancer cell lines. Interestingly, para-Boronic acid derivative (5b) showed selective inhibition against colon cancer cell line, HCT-116 with an IC50 value of 2.35 μM. Besides the emblematic hydrophobic interactions of MDM2 inhibi-tors, derivative 5b was found to exhibit extra hydrogen bonding with GLN59 and GLN72 residues of MDM2 in molecular dynamics (MD) simulation. All the compounds were virtually nontoxic against normal fibroblast cells. Conclusion: Novel compounds were obtained with good anticancer activity especially 6-Chlorochromen-4-one substituted boronic acid derivative 5b. The molecular docking study proposed good activity as a MDM-2 inhibitor suggesting hydrophobic as well as hydrogen bonding interactions with MDM2.
- Bhatia, Richa Kaur,Coutinho, Evans C.,Garg, Ruchika,Kancherla, Satyavathi,Kaur, Maninder,Madan, Jitender,Pissurlenkar, Raghuvir R. S.,Singh, Lakhwinder,Yadav, Manmohan
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p. 212 - 228
(2020/03/10)
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- Design, synthesis and docking study of pyridine and thieno[2,3-b] pyridine derivatives as anticancer PIM-1 kinase inhibitors
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A series of pyridine and thieno[2,3-b]pyridine derivatives have been designed and synthesized as anticancer PIM-1 kinase inhibitors. Thirty-seven compounds were selected by NCI to be tested initially at a single dose (10 μM) in the full NCI 60 cell line panel. Compound 5b showed potent anticancer activity and was tested twice in the five-dose assay which confirmed its potent antitumor activity (GI50 values 0.302–3.57 μM) against all tested tumor cell lines except six cell lines where they showed moderate sensitivity. This compound was sent to NCI biological evaluation committee and still under consideration for further testing. In addition, the most active anticancer compounds in each series, 5b, 8d, 10c, 13h, and 15e, were evaluated for their PIM-1 kinase inhibitory activity. Compound 8d was the most potent one with IC50 = 0.019 μM followed by 5b, 15e, 10c and 13h with IC50 values 0.044, 0.083, 0.128 and 0.479 μM respectively. Moreover, docking study of the most active compounds in PIM-1 kinase active site was consistent with the in vitro activity.
- Abdelaziz, Marwa E.,El-Miligy, Mostafa M.M.,Fahmy, Salwa M.,Mahran, Mona A.,Hazzaa, Aly A.
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p. 674 - 692
(2018/08/02)
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- 5′-Chloro-2,2′-dihydroxychalcone and related flavanoids as treatments for prostate cancer
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Several flavonoids and their biosynthetic precursor chalcones were designed and synthesized to improve the biological effects of the lead compound 2′-hydroxyflavonone against androgen receptor (AR)-dependent transcriptional stimulation. Newly synthesized chalcones 19 and 26 suppressed AR-dependent transcription as well as DHT-dependent growth stimulation at a low micromolar level. These compounds were also effective against ligand-independent constitutively active mutant AR derived from castration-resistant PCa (CRPC). Compounds 19 and 26 showed broad spectrum antiproliferative activity at 5–10 μM against multiple tumor cell lines including androgen-independent and taxane-resistant prostate cancer as well as a multidrug-resistant subline. Mode of action studies suggested that 19 induced sub-G1 accumulation in PC-3 cells by disrupting the microtubule network without affecting cell cycle progression. Furthermore, the in vivo effectiveness of chalcone 19 was confirmed in a xenograft model antitumor assay. Thus, chalcone 19 has the potential to be a bifunctional lead for treatment of AR-dependent PCa at lower doses as well as AR-independent PCa, including CRPC, at higher doses.
- Saito, Yohei,Mizokami, Atsushi,Tsurimoto, Hiroyuki,Izumi, Kouji,Goto, Masuo,Nakagawa-Goto, Kyoko
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supporting information
p. 1143 - 1152
(2018/09/10)
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- One-pot two-step synthesis of 3-iodo-4-aryloxy coumarins and their Pd/C-catalyzed annulation to coumestans
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An efficient protocol for the synthesis of various coumestans from the intramolecular annulation of 3-iodo-4-aryloxy coumarins through C-H activation has been developed. When 3-iodo-4-aryloxy coumarins were treated with 10% Pd/C (0.3 mol% Pd) in the presence of sodium acetate, the corresponding coumestans were produced in good to excellent yield. Reusability of the palladium catalyst was investigated in up to three consecutive cycles and it was found that the yield of the reaction was almost unaltered. Sequential iodination and O-arylation of 4-hydroxy coumarins leading to the 3-iodo-4-aryloxy coumarins were also achieved in a one-pot two-step process starting from aryl iodides in high yield. Pivalic acid was revealed to be the most effective additive for the later method to produce 3-iodo-4-phenoxy coumarins. Different functional groups bearing electron-donating as well as withdrawing groups are also tolerant to the reaction conditions.
- Panda, Niranjan,Mattan, Irshad
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p. 7716 - 7725
(2018/03/01)
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- Acid-Functionalised Magnetic Ionic Liquid [AcMIm]FeCl4 as Catalyst for Oxidative Hydroxylation of Arylboronic Acids and Regioselective Friedel–Crafts Acylation
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An acid-functionalised, magnetic, room-temperature ionic liquid, 1-acyl-3-methylimidazolium tetrachloroferrate ([AcMIm]FeCl4), was synthesised and its optical, magnetic, and thermal properties were investigated. The magnetic moment (0.05402 emu in 2 T magnetic fields) showed strong paramagnetic behaviour, and thermogravimetric analysis indicated very good thermal stability with a decomposition temperature higher than 230 °C. Additionally, [AcMIm]FeCl4 efficiently catalysed the oxidative ipso-hydroxylation of arylboronic acids and regioselective Friedel–Crafts acylation without external organic solvent or additives, such as acids, base, and ligands. This functionalised ionic liquid, [AcMIm]FeCl4, was recycled and reused at least six times without significant loss of its catalytic properties and stability.
- Saha, Arijit,Payra, Soumen,Dutta, Dipa,Banerjee, Subhash
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p. 1129 - 1134
(2017/08/18)
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- Photochemistry of aroyloxiranes: Substituent effect on oxepinones and hydroxyalkenones formation
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The photo-irradiation of some aroyloxiranes with Pyrex filtered UV-light from 125?W medium pressure Hg lamp has been described. These compounds furnished the 2-aryl-4,10-dihydrofuro[3,2-c][1]benzoxepin-10-ones and the hydroxyalkenones by the photochemical irradiation. The product(s) formation/distribution in terms of oxepinones and the hydroxyalkenones largely depended upon the nature of the substituent: the oxiranes having electron-donating groups in their benzoyl moiety gave the hydroxyalkenones while oxiranes having electron-withdrawing groups furnished the oxepinones as the major products. The formation of oxepinones has been envisaged to occur through the heterolytic [Formula presented] bond cleavage of epoxide to give carbonyl ylide intermediates followed by the furo-oxepinone ring formation via [3+2] cycloaddition and of hydroxyalkenones through the initial β-H abstraction followed by epoxide ring opening. The structures of all the compounds (substrates and photoproducts) have been determined on the basis of their spectral data (IR, NMR and Mass).
- Dalal, Aarti,Khanna, Radhika,Berar, Urmila,Kamboj, Ramesh C.
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p. 238 - 245
(2016/07/22)
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- 4 - aromatic amine - coumarin derivatives and its preparation method and medical use (by machine translation)
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The invention relates to the field of pharmaceutical chemistry, in particular relates to a series of 4?Aromatic amine?Coumarin derivatives, method for their preparation and use in medicine, in particular for the treatment of tumor, such as breast cancer, and the like. The present invention relates to compounds of the general structure is as follows, each group in the formula is defined in the specification. (by machine translation)
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Paragraph 0039; 0040; 0074; 0075; 0076
(2016/11/21)
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- Synthesis, biological evaluation, and molecular simulation of chalcones and aurones as selective MAO-B inhibitors
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A series of chalcones and aurones were synthesized and evaluated in vitro as monoamine oxidase inhibitors (MAOi). Our results show that aurones, which had not been previously reported as MAOi, are MAO-B inhibitors. Thus, both families inhibited selectively the B isoform of MAO in the micromolar range, offering novel scaffolds for the design of new and potent MAO inhibitors. The main structural requirements for their activity were characterized with the aid of 3D-QSAR and docking studies.
- Morales-Camilo, Nicole,Salas, Cristian O.,Sanhueza, Claudia,Espinosa-Bustos, Christian,Sepúlveda-Boza, Silvia,Reyes-Parada, Miguel,Gonzalez-Nilo, Fernando,Caroli-Rezende, Marcos,Fierro, Angélica
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p. 685 - 695
(2015/05/27)
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- Synthesis and biological evaluation of 4-(1,2,3-triazol-1-yl)coumarin derivatives as potential antitumor agents
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In this research, a series of 4-(1,2,3-triazol-1-yl)coumarin conjugates were synthesized and their anticancer activities were evaluated in vitro against three human cancer cell lines, including human breast carcinoma MCF-7 cell, colon carcinoma SW480 cell and lung carcinoma A549 cell. To increase the biological potency, structural optimization campaign was conducted focusing on the C-4 position of 1,2,3-triazole and the C-6, C-7 positions of coumarin. In addition, to further evaluate the role of 1,2,3-triazole and coumarin for antiproliferative activity, 9 compounds possessing 4-(piperazin-1-yl)coumarin framework and 3 derivatives baring quinoline core were also synthesized. By MTT assay in vitro, most of the compounds display attractive antitumor activities, especially 23. Further flow cytometry assays demonstrate that compound 23 exerts the antiproliferative role through arresting G2/M cell-cycle and inducing apoptosis.
- Zhang, Wenjuan,Li, Zhi,Zhou, Meng,Wu, Feng,Hou, Xueyan,Luo, Hao,Liu, Hao,Han, Xuan,Yan, Guoyi,Ding, Zhenyu,Li, Rui
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supporting information
p. 799 - 807
(2014/02/14)
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- Lithiation of a silyl ether: Formation of an ortho-fries hydroxyketone
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A hydroxy-directed alkylation of an N,N-diethylarylamide using CIPE-assisted α-silyl carbanions (CIPE=complex-induced proximity effect) has been developed using a simple reagent combination of LDA (lithium diisopropylamide) and chlorosilane. A study of the mechanism, and the application of the procedure to an anionic Snieckus-Fries rearrangement for a highly efficient synthesis of the potent phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002, are reported.
- Lo, Hong-Jay,Lin, Chin-Yin,Tseng, Mei-Chun,Chein, Rong-Jie
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supporting information
p. 9026 - 9029
(2014/09/17)
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- Palladium-catalyzed ortho-CH-bond oxygenation of aromatic ketones
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A palladium-catalyzed C(sp2)-H bond oxygenation reaction is described. This protocol represents the first example of a C-H bond cleavage/C-O bond formation sequence, by employing a ketone moiety as the directing group. With this new catalytic method, a variety of ortho-acylphenols can be easily accessed from arylketones.
- Choy, Pui Ying,Kwong, Fuk Yee
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supporting information
p. 270 - 273
(2013/03/13)
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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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- Imidazolium and pyridinium salts - Solvents influencing the rate and direction of the fries, beckmann, and claisen rearrangements
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The Fries, Beckmann, and Claisen rearrangements have been investigated in ionic liquid media. The effect of the structural elements of the latter on the direction of these rearrangements and the product yields has been studied.
- Katkevica,Zicmanis,Mekss
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experimental part
p. 158 - 169
(2011/08/05)
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- Synthesis of 2-styrylchromones as a novel class of antiproliferative agents targeting carcinoma cells
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A series of 2-styrylchromone analogs were synthesized and examined for their antiproliferative effects on a panel of carcinoma cells. Among the tested agents, only 4m exhibited a moderate activity with an IC50 value of 28.9 μM against PC-3 cells which indicates the selectivity of PC-3 cells in response to 2-styrylchromones. In addition, 4q demonstrated the most antiproliferative effect with an IC50 value of 4.9 μM against HeLa cells. Flow cytometric analysis and DAPI staining revealed that HeLa cells exposed to 4q as low as 5 μM induced cell death through sub-G1 arrest and DNA fragmentation. Furthermore, CoMFA analysis of tested 2-styrylchromones resulted in a q2 of 0.459 to generate a 3D-QSAR model on BT483 cell line. Together, these results suggest a potential structural optimization and pharmacological study of 2-styrylchromones.
- Shaw, Arthur Y.,Chang, Chun-Yi,Liau, Hao-Han,Lu, Pei-Jung,Chen, Hui-Ling,Yang, Chia-Ning,Li, Hao-Yi
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experimental part
p. 2552 - 2562
(2009/09/30)
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- Synthesis of methoxy-substituted phenols by peracid oxidation of the aromatic ring
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A novel benign protocol for the preparation of hydroxy-methoxybenzene derivatives is disclosed. By utilizing this protocol, activated aromatic compounds such as l,3-dimethoxy-2-methyl-benzene and 1-(2,6-dimethoxyphenyl) ethanone are smoothly converted to the corresponding monohydroxylated compound. The reaction can be considered to be a normal aromatic electrophilic substitution reaction, and the regioselectivity for the reaction thus follows the similar rules as for electrophilic substitutions. The protocol is composed by benign reagents, namely, hydogenperoxide, acetic acid, and p-toluene sulfonic acid, which lead to the production of ethaneperoxoic acid in situ. The ethaneperoxoic acid operates as the hydroxylating reagent. The hydroxylation reaction is completed within a short period and requires moreover only mild experimental conditions, which make this novel protocol a green, cheap, and rapid process leading to hydroxy-methoxybenzene derivatives. The proposed reaction mechanism is supported by density functional theory and NMR spectroscopy experiments. The mechanism is constituted by two discrete steps: (a) addition of OH+ to the most nucleophilic carbon atom of the aromatic ring, which is the rate-determining step, and (b) the loss of the proton from the aromatic ring.
- Bjorsvik, Hans-Rene,Occhipinti, Giovanni,Gambarotti, Cristian,Cerasino, Leonardo,Jensen, Vidar R.
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p. 7290 - 7296
(2007/10/03)
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- QSAR studies of paeonol analogues for inhibition of platelet aggregation
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Various paeonol analogues were synthesized and tested in vitro as inhibitors of platelet aggregation. Structural properties (or descriptors) of paeonol analogues were calculated and the structure-activity relationships were determined. Several multiple linear and nonlinear regression models and back-propagation neural network model were tested and the latter using relative positive charge, hydration energy, and hydrophilic factor as inputs gave the best data fitting with R2 = 0.89 and qpre2=0.66. The correlation coefficient between antiplatelet inhibition activity with an interaction energy between the paeonol compounds with COX-1 enzyme is only 0.39.
- Doble, Mukesh,Karthikeyan,Padmaswar,Akamanchi
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p. 5996 - 6001
(2007/10/03)
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- Selectivity adjustment in the cleavage of allyl phenyl and methyl phenyl ethers with boron trifluoride-methyl sulfide complex
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Cleavage of model allyl phenyl and methyl phenyl ethers with boron trifluoride-methyl sulfide complex is described. The demonstrated strong dependence of the reaction rate on the substitution pattern of the phenyl ring and the reaction conditions make it potentially possible to selectively cleave a single methoxy (or allyloxy) group in poly methoxy (or allyloxy) compounds. Georg Thieme Verlag Stuttgart.
- Konieczny, Marek T.,Maciejewski, Grzegorz,Konieczny, Wojciech
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p. 1575 - 1577
(2007/10/03)
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- Photohydrodimerization of 6-methoxyflavone to 6,6″-dimethoxy-2, 2″-biflavanones
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6-Methoxyflavone (7) easily afforded two hydrodimers of rac-6,6″-dimethoxy-2,2″-biflavanone (8a) and meso-6,6″- dimethoxy-2,2″-biflavanone (8b) and one reductive product of 6-methoxyflavanone (9) by using photolysis with the electron-donating amines including triethylamine, 2-(N,N-dimethylamino)ethanol or N,N-dimethylaniline in solvents of acetonitrile, benzene or methylene dichloride. They were found to give higher yields of rac-6,6″-dimethoxy-2,2″-biflavanone (8a) and meso-6,6″-dimethoxy-2,2″-biflavanone (8b) (38.7% and 4.5%, 35.3% and 6.2%, respectively) in the reaction conditions of 1/10 molar ratio of 6-methoxyflavone (7) to triethylamine in a solvent of acetonitrile with irradiation of twenty-four hours by using 306 nm and 352 nm lamps.
- Chen, Arh-Hwang,Kuo, Wei-Bao,Chen, Chia-Wen
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p. 1389 - 1394
(2007/10/03)
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- Bismuth triflate-catalyzed fries rearrangement of aryl acetates
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Bismuth triflate was found to be an efficient catalyst in the Fries rearrangement of phenyl or 1-naphthyl acetates. Both reactions proceeded smoothly with a catalytic amount of bismuth triflate (10 mol%) to afford the corresponding hydroxyaryl ketone in moderate to good yields in most cases.
- Ollevier, Thierry,Desyroy, Valerie,Asim, Muhammad,Brochu, Marie-Christine
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p. 2794 - 2796
(2007/10/03)
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- Structure-activity relationships of a novel class of endothelin-A receptor antagonists and discovery of potent and selective receptor antagonist, 2-(benzo[1,3]dioxol-5-yl)-6-isopropyloxy-4- (4-methoxyphenyl)-2H-chromene-3-carboxylic acid (S-1255). 1. Study on structure-activity relationships and basic structure crucial for ETA antagonism
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A novel series of endothelin-A (ETA) selective receptor antagonists having a 2H-chromene skeleton are described. A lead compound, 2-(benzo[1,3] dioxol-5-yl)-2H-chromene-3-carboxylic acid (3), was found by modifications of our own angiotensin II antagonist. A structure-activity relationship (SAR) study of 3 reveals that the structural requirements essential for potent and selective ETA receptor binding affinity are the m,p-methylenedioxyphenyl, carboxyl, and isopropoxy groups at the 2-, 3-,and 6-positions, respectively, on the (R)-2H-chromene skeleton. The substituent at the 4-position is also important for improving the activity, and various hydrophobic functional groups of 6-9 ? such as liner, branched, and cyclic aliphatic groups, unsubstituted and substituted aryl groups, and even halogen atoms were acceptable. These results suggest that (R)-2-(benzo[1,3]dioxol-5-yl)-6-isopropoxy-2H-chromene-3-carboxylic acid, formula 108, is the crucial basic structure to be recognized by the ETA receptor. The most potent compound is (R)-48 (S-1255), which binds to the ETA receptor with an IC50 value of 0.19 nM and is 630-fold selective for the ETA receptor than for the ETB receptor. This compound has 55% oral bioavailability in rats. On the basis of the SAR, the roles of each substituent in the receptor binding are discussed.
- Ishizuka, Natsuki,Matsumura, Ken-Ichi,Sakai, Katsunori,Fujimoto, Masafumi,Mihara, Shin-Ichi,Yamamori, Teru
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p. 2041 - 2055
(2007/10/03)
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- 2-aminopyridine derivatives and combinatorial libraries thereof
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The present invention relates to novel 2-aminopyridine derivative compounds of the following formula: wherein R1to R5have the meanings provided herein. The invention further relates to combinatorial libraries containing two or more such compounds, as well as methods of preparing 2-aminopyridine derivative compounds.
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- Synthesis of (±)-3,3′-bis(4-hydroxy-2H-benzopyran): A literature correction
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The synthesis of bisbenzopyran-4-ol (1) was performed through the key steps of iodination, nickel(0)-modified Ullmann-type reaction, hydrogen-transfer hydrogenation and diastereoselective reduction. The X-ray diffraction experiment of compound 9 confirmed that the reported structure in the literature was not the real natural product.
- Hong, Ran,Feng, Jun,Hoen, Rob,Lin, Guo-Qiang
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p. 8685 - 8689
(2007/10/03)
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- Synthetic Utility and Mechanistic Implications of the Fries Rearrangement of Hydroquinone Diesters in Boron Trifluoride Complexes
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Reactions of boron trifluoride methyl and ethyl etherate complexes with hydroquinone diesters yield monomethyl and monoethyl derivatives of acetylhydroquinones. The use of sterically hindered boron trifluoride etherate complexes results in acetylhydroquinone derivatives. This procedure represents a one-step synthesis of acetylhydroquinone derivatives, important building blocks for a variety of synthetic applications.
- Boyer, Jessica L.,Krum, Jodie E.,Myers, Michael C.,Fazal, Aleem N.,Wigal, Carl T.
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p. 4712 - 4714
(2007/10/03)
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- Synthesis and in-vitro evaluation of platelet aggregation inhibitory activity of paeonol and its analogues
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Paeonol (1-(2-hydroxy-4-methoxyphenyl)ethanone) and a series of substituted 1-(2-hydroxyphenyl)ethanone derivatives were synthesized and screened as inhibitors of platelet aggregation. The compounds with the greatest anti-platelet potential among the series tested were 1-(2,5-dihydroxyphenyl)ethanone (65.36% inhibition at 300 μM against 5 μM ADP), paeonol(36.31%), 1-(2-hydroxy-5-methoxyphenyl)ethanone (24.47%), 1-(2-hydroxy-5-nitrophenyl) ethanone (30.40%) and 1-(5-chloro-2-hydroxy-4-methylphenyl)ethanone (24.43%).
- Akamanchi,Padmawar,Thatte,Rege,Dahanukar
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p. 323 - 329
(2007/10/03)
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- Tandem Fries Reaction-Conjugate Addition under Microwave Irradiation in Dry Media; One-pot Synthesis of Flavanones
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An AlCl3-ZnCl2 mixture supported on silica gel is found to be an efficient medium for the Fries rearrangement of acyloxybenzene or naphthalene derivatives in solvent-free conditions under microwave irradiation.
- Moghaddam, Firouz Matloubi,Ghaffarzadeh, Mohammad,Abdi-Oskoui, Seyed Hossein
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p. 574 - 575
(2007/10/03)
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- Norrish Type I Photoreaction in the Presence of Phenols; an Intermolecular Photo-Fries Rearrangement
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Pinacolone photolysis in the presence of phenols leads to phenyl acetates and hydroxy acetophenones; Norrish type I cleavage and subsequent hydrogen abstraction from the phenol by the tert-butyl radical gives rise to acyl-aryloxy radical pairs which recombined constituting an intermolecular photo-Fries rearrangement.
- Jimenez, M. Consuelo,Leal, Pablo,Miranda, Miguel A.,Tormos, Rosa
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p. 2009 - 2010
(2007/10/02)
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- Studies of the selective O-alkylation and dealkylation of flavonoids. XVI. Demethylation of 2'-methoxyacetophenones with anhydrous aluminum chloride or bromide in acetonitrile
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Demethylation of 2'-methoxyacetophenones with anhydrous aluminum chloride in acetonitrile was studied to survey its scope and limitations. The mechanism which the reaction proceeds via sterically constrained intermediates was proposed from the substituent effects. Additionally, dealkylation of 2'-benzyloxy-, 2'-ethoxy-, and 2'-isopropoxyacetophenones with two demethylating reagents, hydrochloric acid in acetic acid and anhydrous aluminum bromide in acetonitrile, was studied. It was found that the reactivity was greatly affected by the steric factor between the alkoxyl group and reagent. This behavior may have wide application in selection of protecting groups in organic synthesis.
- Kawamura,Takatsuki,Torii,Horie
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p. 511 - 515
(2007/10/02)
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- New photochemical approaches to the synthesis of chromones
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Irradiation of the p-methoxyphenyl and p-methylphenyl esters of 2-butynoic, propynoic, 3-(ethylenedioxy)butanoic, 3,3-dimethoxypropanoic and 3-oxobutanoic acids (1-3) affords the corresponding photo-Fries products 4-6. Compound 5a is converted in part into the acetophenone 7a, by way of a Norrish type II photo-reaction, while compound 6a is reluctant to undergo this process, in spite of the fact that it also possess γ-carbonyl hydrogen atoms. From the preparative point of view, the photorearrangement of the esters 1a-d and 2a,c-d is exploitable, while that of 3a proceeds with a lower yield. The differences found in the photochemical behaviour of 2a and 3a show the sharp influence of the acetal group on the course of the reaction. Compounds 4-6 are representative model compounds valuable as direct chromone precursors; in fact, they can be readily cyclized to the chromones 10 under basic or acidic conditions.
- Alvaro, Mercedes,Garcia, Hermenegildo,Iborra, Sara,A. Miranda, Miguel,Primo, Jaime
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p. 143 - 148
(2007/10/02)
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- Dibenzocyclooctene-, Dibenzochalcocine-, and Diarenochalconinediones
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2,2'-Oxybis-, -thiobis-, and -methylenebisbenzoic esters 2a-c react with methyllithium in ether to give low yields of 5H-dibenzochalcocine-5,7(6H)-diones 6a, 7a, and dibenzocyclooctene-5,7(6H,12H)-dione (8), respectively.Very good yields of such heterocycles with oxygen (6a-h, 37), sulfur (7a-h, 38) and selenium (36) as key atom are obtained when diaryl ethers (21, 22, 25), -sulfides (27, 29, 30), and -selenides (33) that contain 2'-acetyl- (or -propionyl-) and 2-methoxycarbonyl groups are treated with sodium hydride in boiling toluene.Analogously are prepared the dibenzoxonine-11,13(6H,12H)diones 62a-c and 7H-benzonaphthothionine-7,9-(8H)-dione (65) which are expanded by one ring member.In the analogous reaction of a corresponding benzophenone derivative 35, spiro-3(2H),3'-dione (41) is formed in a tandem reaction. - Under phase transfer conditions the dibenzochalcocinediones 6, 7, 36 and also the corresponding nitrogen cycles 5 react to give mixtures of C- (42-45) and O-alkyl derivatives (46-49).Methyllithium and diisobutylaluminium hydride provide the carbinols 50-54.With bromine and SO2Cl2, respectively, the methylene group is mono- or dihalogenated to the products 56, 57; defined nitration was only possible for the oxacycle 6a.
- Hellwinkel, Dieter,Bohnet, Siegbert
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p. 1151 - 1174
(2007/10/02)
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- The Photo-Fries Rearrangement in the Presence of Potassium Carbonate: A Convenient Synthesis of ortho-Hydroxyacetophenones
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Phenyl acetates 1 are converted into o-hydroxyacetophenones 2 in 78-90percent yields by photolysis in hexane solution in the presence of potassium carbonate.
- Garcia, Hermenegildo,Primo, Jaime,Miranda, Miguel Angel
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p. 901 - 902
(2007/10/02)
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- PHOTOLYSIS OF 2-ARYLOXY- OR 2-ARYLTHIO-1,3-BENZODIOXAN-4-ONES
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Photolysis of 1,3-benzodioxan-4-ones 3b and 4a gives mainly products derived from photorearrangement, photoreduction and/or photosolvolysis.These results closely parallel those obtained by irradiation of the isomeric open-chain compounds 1b and 2a.A mechanism involving the intermediacy of radical pairs A and B, generated by successive homolysis of the aryloxy- or arylthio-carbon and carbonyl-oxygen bonds, is proposed.
- Diaz-Mondejar, M. Rosa,Miranda, Miguel A.
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p. 1125 - 1131
(2007/10/02)
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- REGULATION OF ENZYMIC OXIDATION OF INDOLE-3-ACETIC ACID BY PHENOLS: STRUCTURE-ACTIVITY RELATIONSHIPS
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Mono- and diphenols were tested for their effects on the decarboxylation of IAA catalysed by purified horseradish peroxidase (EC 1.11.1.7) in the presence or absence of 2,4-dichlorophenol (DCP).The number of hydroxyl groups and their position relative to each other and the nature and position of other substituents on the aromatic ring were found to affect the activity.Although the effects were complex, the following generalizations may be made. (1) Monophenols produce activation when no other cofactor is present. p-Substituted monophenols are more active than o- or m compounds.In the presence of DCP, the activity varies from slight activation to strong inhibition. (2) m-Diphenols also produce activation in the absence of other cofactors while o- and p-diphenols, with the exception of 3,4-dihydroxyacetophenone and 3,4-dihydroxypropiophenone, produce strong inhibition in the presence or absence of DCP.The o-diphenols are degraded in the IAA-oxidizing enzyme system and thus produce only a temporary inhibition. (3) m-Diphenols and 3,4-dihydroxyacetophenone produce a sustained inhibition in the presence of DCP. (4) Substitution at position 2 significantly alters the activity of m-diphenols. (5) o-Methylation alters the activity of most o-diphenols.In the absence DCP, o-methoxyphenols and certain other phenols such as 3,4-dihydroxyacetophenone and 2,6-dihydroxyacetophenone either promote or inhibit IAA oxidation depending on concentration.Key Word Index-Phenols; indole-3-acetic acid; IAA-oxidase; peroxidase.
- Lee, Tsung T.,Starratt, Alvin N.,Jevnikar, John J.
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p. 517 - 524
(2007/10/02)
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- Synthesis of C-Ring-Functionalized A-Ring-Aromatic Trichothecane Analogues
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15,16-Dinor-4α-acetoxy-8-methoxy-6,8,10-trichothecatriene 12,13-epoxide (11) was prepared from 2α-(2-acetoxy-5-methoxyphenyl)-2β-methyl-3α-acetoxycyclopentanone (8) in three steps (bromination, DBN-induced cyclization, and spiroepoxidation).The cyclopentanone 8 was prepared from the hemiketal 6a which was prepared from 2'-acetoxy-5'-methoxyacetophenone (3f) in a reaction sequence involving the boron trifluoride catalyzed aldol addition of 1,2-bis(trimethylsilyloxy)cyclobutene followed by a trifluoroacetic acid catalyzed pinacol rearrangement of the cyclobutanone intermediate.
- Anderson, Wayne K.,Lee, George E.
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p. 501 - 506
(2007/10/02)
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- Psychotomimetic phenylisopropylamines. 5. 4 alkyl 2,5 dimethoxyphenylisopropylamines
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A homologous series of 4 alkyl 2,5 dimethoxyphenylisopropylamines (alkyl = H through n C5H11 and t C4H9) was synthesized and compared with mescaline as serotonin agonists in a sheep umbilical preparation. The three carbon homolog 6d was found to be the most potent of the straight chain series in accordance with its observed psychotomimetic effectiveness in man.
- Shulgin,Dyer
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p. 1201 - 1204
(2007/10/06)
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