- An efficient method to prepare aryl acetates by the carbonylation of aryl methyl ethers or phenols
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Synthesis of valuable chemicals from lignin based compounds is critical for the application of biomass. Here, we develop a method of preparing aryl acetates by the carbonylation of aryl methyl ethers or phenols under low CO pressure. Good to excellent yields of aryl acetates were obtained using different substrates, and a possible reaction mechanism was proposed by conducting a series of control experiments. This method may provide a potential way for the utilization of lignin.
- Zhang, Dejin,Yang, Guoqiang,Xiong, Junping,Liu, Jia,Hu, Xingbang,Zhang, Zhibing
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p. 2683 - 2687
(2021/02/16)
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- Copper-catalyzed oxidative benzylic C(sp3)-H amination: Direct synthesis of benzylic carbamates
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A new efficient strategy to access benzylic carbamates through C-H activation is reported. The use of a catalytic amount of a Cu(i)/diimine ligand in combination with NFSI ((PhSO2)2NF) or F-TEDA-PF6 as oxidants and H2NCO2R as an amine source directly leads to the C-N bond formation at the benzylic position. The mild reaction conditions and the broad substrate scope make this transformation a useful method for the late-stage incorporation of a ubiquitous carbamate fragment onto hydrocarbons. This journal is
- Liu, Shuai,Achou, Rapha?l,Boulanger, Coline,Pawar, Govind,Kumar, Nivesh,Lusseau, Jonathan,Robert, Frédéric,Landais, Yannick
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supporting information
p. 13013 - 13016
(2020/11/05)
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- Selective hydrodeoxygenation of hydroxyacetophenones to ethyl-substituted phenol derivatives using a FeRu?SILP catalyst
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The selective hydrodeoxygenation of hydroxyacetophenone derivatives is achieved opening a versatile pathway for the production of valuable substituted ethylphenols from readily available substrates. Bimetallic iron ruthenium nanoparticles immobilized on an imidazolium-based supported ionic liquid phase (Fe25Ru75?SILP) show high activity and stability for a broad range of substrates without acidic co-catalysts. This journal is
- Bordet, Alexis,Goclik, Lisa,Leitner, Walter,Offner-Marko, Lisa
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supporting information
p. 9509 - 9512
(2020/09/02)
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- Environmentally responsible, safe, and chemoselective catalytic hydrogenation of olefins: ppm level Pd catalysis in recyclable water at room temperature
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Textbook catalytic hydrogenations are typically presented as reactions done in organic solvents and oftentimes under varying pressures of hydrogen using specialized equipment. Catalysts new and old are all used under similar conditions that no longer reflect the times. By definition, such reactions are both environmentally irresponsible and dangerous, especially at industrial scales. We now report on a general method for chemoselective and safe hydrogenation of olefins in water using ppm loadings of palladium from commercially available, inexpensive, and recyclable Pd/C, together with hydrogen gas utilized at 1 atmosphere. A variety of alkenes is amenable to reduction, including terminal, highly substituted internal, and variously conjugated arrays. In most cases, only 500 ppm of heterogeneous Pd/C is sufficient, enabled by micellar catalysis used in recyclable water at room temperature. Comparison with several newly introduced catalysts featuring base metals illustrates the superiority of chemistry in water.
- Gallou, Fabrice,Gao, Eugene S.,Lipshutz, Bruce H.,Takale, Balaram S.,Thakore, Ruchita R.
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supporting information
p. 6055 - 6061
(2020/10/14)
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- Monodisperse CuPt alloy nanoparticles assembled on reduced graphene oxide as catalysts in the transfer hydrogenation of various functional organic groups
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We present herein a new nanocatalyst, namely binary CuPt alloy nanoparticles (NPs) supported on reduced graphene oxide (CuPt-rGO), as a highly active heterogeneous catalyst for the transfer hydrogenation (TH) protocol that is demonstrated to be applicable over the reduction of various unsaturated organic compounds (olefins, aldehydes/ketones and nitroarenes) in aqueous solutions at room temperature. CuPt alloy NPs were synthesized by the co-reduction of metal (II) acetylacetonates by borane-tert-butylamine (BTB) complex in hot oleylamine (OAm) solution and then assembled on reduced graphene oxide (rGO) via ultrasonic-assisted liquid phase self-assembly method. The structure of yielded CuPt NPs and CuPt-rGO nanocatalyst were characterized by TEM, XRD and ICP-MS. The activity of Cu7Pt3-rGO nanocatalysts were then tested for the THs that were conducted in a commercially available high-pressure tube using water as sole solvent and ammonia borane as a hydrogen donor at room temperature. The presented catalytic TH protocol was successfully applied over nitroarenes, olefines and aldehydes/ketones, and all the tested compounds were converted to corresponding reduction products with the yields reaching up to 99% under ambient conditions. Moreover, the Cu7Pt3-rGO nanocatalyst was also reusable in the TH by providing 99% yield after five consecutive runs in TH of nitrobenzene as an example.
- Ganjehyan, Khadijeh,Ni?anc?, Bilal,Sevim, Melike,Da?tan, Arif,Metin, ?nder
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- New photocatalytic fixed-point deuteration method for carbon-carbon unsaturated bonds
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The invention relates to a new photocatalytic fixed-point deuteration method for carbon-carbon unsaturated bonds. The method is characterized in that an olefin or alkyne compound and a deuterium source undergoes a deuteration reaction under the catalysis of a light source and a photocatalyst to obtain a deuterated product, wherein the deuterium source is deuterated water, deuterated alcohol or deuterated acid, and the reaction temperature is between room temperature and 80 DEG C. The fixed-point deuteration reaction of the olefin or alkyne compound is realized under the photocatalysis action of the photocatalyst with environmentally-friendly and cheap deuterated water or a deuteration reagent as a deuterium source to substitute deuterium gas. Compared with traditional deuteration reactions, the method has a higher selectivity, milder reaction conditions and higher economical suitability, and is suitable for large-scale deuterated chemical substance production.
- -
-
Paragraph 0055; 0057; 0058; 0061
(2019/01/21)
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- Transition-Metal- and Halogen-Free Oxidation of Benzylic sp 3 C-H Bonds to Carbonyl Groups Using Potassium Persulfate
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Aryl carbonyl compounds including acetophenones, benzophenones, imides, and benzoic acids are prepared from benzyl substrates using potassium persulfate as oxidant with catalytic pyridine in acetonitrile under mild conditions. Neither transition metals nor halogens are involved in the reactions.
- Hu, Yixin,Zhou, Lihong,Lu, Wenjun
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supporting information
p. 4007 - 4016
(2017/08/29)
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- Synthesis and SAR Study of Anticancer Protoflavone Derivatives: Investigation of Cytotoxicity and Interaction with ABCB1 and ABCG2 Multidrug Efflux Transporters
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There is a constant need for new therapies against multidrug-resistant (MDR) cancer. Natural compounds are a promising source of novel anticancer agents. We recently showed that protoflavones display activity in MDR cancer cell lines that overexpress the P-glycoprotein (P-gp) drug efflux pump. In this study, 52 protoflavones, including 22 new derivatives, were synthesized and tested against a panel of drug-sensitive parental cells and their MDR derivatives obtained by transfection with the human ABCB1 or ABCG2 genes, or by adaptation to chemotherapeutics. With the exception of protoapigenone, identified as a weak ABCG2 substrate, all protoflavones bypass resistance conferred by these two transporters. The majority of the compounds were found to exhibit mild to strong (up to 13-fold) selectivity against the MCF-7Dox and KB-V1 cell lines, but not to transfected MDR cells engineered to overexpress the MDR transporters. Our results suggest that protoflavones can overcome MDR cancer by evading P-gp-mediated efflux.
- Dankó, Balázs,Tóth, Szilárd,Martins, Ana,Vágv?lgyi, Máté,Kúsz, Norbert,Molnár, Joseph,Chang, Fang-Rong,Wu, Yang-Chang,Szakács, Gergely,Hunyadi, Attila
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p. 850 - 859
(2017/06/13)
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- Efficient Water Reduction with sp3-sp3 Diboron(4) Compounds: Application to Hydrogenations, H–D Exchange Reactions, and Carbonyl Reductions
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A series of crystalline sp3-sp3 diboron(4) compounds were synthesized and shown to promote the facile reduction of water with dihydrogen formation. The application of these diborons as simple and effective dihydrogen and dideuterium sources was demonstrated by conducting a series of selective reductions of alkynes and alkenes, and hydrogen–deuterium exchange reactions using two-chamber reactors. Finally, as the water reduction reaction generates an intermediate borohydride species, a range of aldehydes and ketones were reduced by using water as the hydride source.
- Flinker, Mathias,Yin, Hongfei,Juhl, René W.,Eikeland, Espen Z.,Overgaard, Jacob,Nielsen, Dennis U.,Skrydstrup, Troels
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supporting information
p. 15910 - 15915
(2017/11/23)
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- Design, synthesis and docking studies of novel thienopyrimidine derivatives bearing chromone moiety as mTOR/PI3Kα inhibitors
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Two series of thienopyrimidine derivatives (10a-k, 16a-j) bearing chromone moiety were designed and synthesized. All the compounds were evaluated for inhibitory activity against mTOR kinase at a concentration of 10uM. Four selected compounds were further evaluated for the IC50 values against mTOR kinase, PI3Kα kinase and two cancer cell lines. Some of the target compounds exhibited moderate to excellent mTOR/PI3Kα kinase inhibitory activity and cytotoxicity. The most promising compound 16i showed good inhibitory activity against mTOR/PI3Kα kinase and good antitumor potency for H460 and PC-3 cell lines with IC50 values of 0.16 ± 0.03 μM, 2.35 ± 0.19 μM, 1.20 ± 0.23 μM and 0.85 ± 0.04 μM, which were 8.6, >5, 7.9 and 19.1 times more active than compound I (1.37 ± 0.07 μM, >10 μM, 9.52 ± 0.29 μM, 16.27 ± 0.54 μM), respectively. Structure-activity relationships (SARs) and docking studies indicated that the chromone moiety is necessary for the potent antitumor activity and cytotoxicity of these compounds. Substitution of the chromone moiety at the 6-position has a significant impact to the inhibitory activity, in particular a carboxylic acid group, produced the best potency.
- Zhu, Wufu,Chen, Chen,Sun, Chengyu,Xu, Shan,Wu, Chunjiang,Lei, Fei,Xia, Hui,Tu, Qidong,Zheng, Pengwu
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- Iridium(I)/N-Heterocyclic Carbene Hybrid Materials: Surface Stabilization of Low-Valent Iridium Species for High Catalytic Hydrogenation Performance
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An IrI(NHC)-based hybrid material was prepared using a methodology which allowed the precise positioning and isolation of the Ir centers along the pore channels of a silica framework. The full characterization of the material by solid-state NMR spectroscopy showed that the supported Ir sites were stabilized by the silica surface, as low-coordinated single-site complexes. The material is extremely efficient for the hydrogenation of functional alkenes. The catalytic performance (TOF and TON) is one to two orders of magnitude higher than those of their molecular Ir analogues, and could be related to the prevention of the bimolecular deactivation of Ir complexes observed under homogeneous conditions. Lending support: Homogeneous positioning of IrI complexes within the pore-channels of a silica framework stabilizes a low-valent IrI species and leads to drastically improved catalyst efficiency. Catalyst decomposition by formation of iridium-hydride clusters is prevented by the attachment to the support. Mes=2,4,6-trimethylphenyl.
- Romanenko, Iuliia,Gajan, David,Sayah, Reine,Crozet, Delphine,Jeanneau, Erwan,Lucas, Christine,Leroux, Lénaic,Veyre, Laurent,Lesage, Anne,Emsley, Lyndon,Lac?te, Emmanuel,Thieuleux, Chloé
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supporting information
p. 12937 - 12941
(2015/11/02)
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- Chelating Bis-N-heterocyclic Carbene-Palladium(II) Complexes for Oxidative Arene C-H Functionalization
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Bis-N-heterocyclic carbene (NHC)-chelated palladium(II) complexes have been synthesized, characterized fully including single-crystal X-ray structural analyses, and utilized for the first time toward catalytic oxidative C-H functionalization of arenes with PhI(OAc)2 and N-bromosuccinimide. (Figure Presented).
- Desai, Sai Puneet,Mondal, Moumita,Choudhury, Joyanta
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p. 2731 - 2736
(2015/06/30)
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- PPARG MODULATORS FOR TREATMENT OF OSTEOPOROSIS
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The invention provides methods of treatment of a progressive bone disease, such as osteoporosis, Paget's Disease, multiple myeloma, or hyperparathyroidism, comprising administration of an effective amount of a non-agonist PPARG modulator to a patient afflicted with the disease.
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Page/Page column 231; 232
(2015/11/09)
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- Influence of the 4-substituents on the reversal of enantioselectivity in the asymmetric hydroformylation of 4-substituted styrenes with PtCl(SnCl 3)[(2 S, 4 S)-BDPP]
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The enantioselectivity of the asymmetric hydroformylation of 4-substituted styrenes in the presence of an in situ catalyst, formed from PtCl(SnCl 3)[(2S,4S)-BDPP] and tin(II) chloride, was influenced by the reaction temperature. The preferred formation of the S and the R enantiomers of the branched aldehyde regioisomers (2a-g) was observed at low and high temperatures, respectively. The electron-donor or electron-acceptor properties of the para substituents of styrene show correlation with the changes in enantioselectivity, especially with the reversal temperature of the enantioselectivity. The reversibility of the formation of the Pt-branched alkyl intermediates, leading to the corresponding R and S enantiomers of 2-arylpropanals, depends on the Hammett constants. The electronic effect of para substituents was investigated by quantum chemical methods employing the simple olefin adducts [HPt(PH 3)2(olefin)(SnCl3)]. Excellent linear correlation was found between the para substituent constants and the electrostatic potential at nuclei of the platinum atom. Equally good correlation has been established for the other atoms as well in the coordination sphere of Pt.
- Pongracz, Peter,Papp, Tamara,Kollar, Laszlo,Kegl, Tamas
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supporting information
p. 1389 - 1396
(2014/04/17)
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- In situ generated acylimidazolium acetate as an efficient catalyst and acylating agent for the acetylation of alcohols, phenols, and amines at ambient temperature
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Acylimidazolium acetate was readily prepared in situ from the reaction of imidazole with acetic anhydride and subsequently acted as a catalyst and acylating agent for the efficient acetylation of alcohols, phenols, and amines at ambient temperature.
- Nowrouzi, Najmeh,Alizadeh, Seyedeh Zahra
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p. 1787 - 1790
(2013/10/21)
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- Design and syntheses of novel N′-((4-oxo-4H-chromen-3-yl)methylene) benzohydrazide as inhibitors of cyanobacterial fructose-1,6-/sedoheptulose-1,7- bisphosphatase
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Cyanobacterial fructose-1,6-/sedoheptulose-1,7-bisphoshatase (Cy-FBP/SBPase) is an important target enzyme for finding inhibitors to solve harmful algal bloom (HAB). In this study, as potential inhibitors of Cy-FBP/SBPase, a series of novel chromone-connecting benzohydrazone compounds (Novel N′-((4-oxo-4H-chromen-3-yl)methylene)benzohydrazide) were designed and synthesized. Their inhibitory activities against Cy-FBP/SBPase were further examined in vitro. Some of these compounds, such as f6-f8, f11, f12 and f16, exhibit higher inhibitory activities (IC50 = 11.2-16.1 μM), especially, the compound f7 was identified as the most potent inhibitor with IC50 value of 11.2 μM. The probable binding-mode of compound f7 was further analyzed carefully by molecular docking methods. These results indicate that compound f7 could be used as a lead compound for further optimization and might have potential to be developed as a new algicide.
- Tu, Qi-Dong,Li, Ding,Sun, Yao,Han, Xin-Ya,Yi, Fan,Sha, Yibamu,Ren, Yan-Liang,Ding, Ming-Wu,Feng, Ling-Ling,Wan, Jian
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p. 2826 - 2831
(2013/06/27)
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- O-acylation of substituted phenols with various alkanoyl chlorides under phase-transfer catalyst conditions
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Esterification of several types of mono-and disubstituted phenols with various mono-and dialkanoyl chlorides was performed in phase-transfer catalysis conditions, using tetrabutylammonium chloride in a mixture of aqueous NaOH and dichloromethane. The process is particularly efficient (almost quantitative yields) as well as rapid (only 5 min reaction time, at a temperature of0°C). Taylor & Francis Group, LLC.
- Simion, Alina Marieta,Hashimoto, Iwao,Mitoma, Yoshiharu,Egashira, Naoyoshi,Simion, Cristian
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experimental part
p. 921 - 931
(2012/02/01)
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- N-BENZYLINDOLE MODULATORS OF PPARG
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The invention provides molecular entities that bind with high affinity to PPARG (PPARγ), and inhibit kinase-mediated (e.g., cdk5-mediated) phosphorylation of PPARG, but do not exert an agonistic effect on PPARG. Compounds of the invention can be used for treatment of conditions in patients wherein PPARG plays a role, such as diabetes, insulin resistance, impaired glucose tolerance, pre-diabetes, hyperglycemia, hyperinsulinemia, obesity, or inflammation. Side effects such as significant weight gain, edema, impairment of bone growth or formation, or cardiac hypertrophy, or any combination thereof, can be avoided in the mammal receiving the compound. Methods of preparation of the compounds, bioassay methods for evaluating compounds of the invention as non-agonistic PPARG binding compounds, and pharmaceutical compositions are also provided.
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Page/Page column 118
(2012/12/14)
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- Hydroformylation of styrene in the presence of platinum(II) complex catalysts incorporating cyclic phosphines and phosphonous diesters as P-ligands
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The hydroformylation activity of various 5- and 6-membered P-heterocycles was investigated in platinum-catalysed hydroformylation of styrene. All of the tested ligands, such as the phosphole-, oxaphosphorine- and phoshinine-based ligands proved to be catalytically active. Especially good aldehyde selectivities were obtained with the chelating diphenylphosphino- tetrahydrophosphinine and diphenylphosphino-hexahydrophosphinine ligands. While the two aldehyde regioisomers were formed close to equimolar amounts with the monodentate ligands, high branched selectivities were observed with the chelating ones. The effect of the 4-substitution of the parent styrene on chemo- and regioselectivity was investigated.
- Pongrácz, Péter,Kollár, László,Kerényi, Andrea,Kovács, Viktória,Ujj, Viktória,Keglevich, Gy?rgy
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experimental part
p. 2234 - 2237
(2011/06/22)
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- Platinum(II) complexes incorporating racemic and optically active 1-alkyl-3-phospholenes and 1-propyl-phospholane P-ligands: Synthesis, stereostructure, NMR properties and catalytic activity
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Racemic and optically active 1-propyl- and 1-butyl-3-methyl-3-phospholene oxides, as well as 1-propyl-3-methylphospholane oxides were converted after deoxygenation to the corresponding phosphine-borane and phopshine-platinum complexes. Stereostructure of the novel platinum complexes with a propyl group on the phosphorus atom was evaluated by quantum chemical calculations. The complexes displayed characteristic properties regarding their NMR spectra and showed unusual regioselectivity as catalysts in the hydroformylation of styrene derivatives. Ee-s up to 21% were obtained in the presence of optically active Pt-complex precursors.
- Keglevich, Gy?rgy,Bagi, Péter,Sz?llsy, áron,K?rtvélyesi, Tamás,Pongrácz, Péter,Kollár, László,Drahos, László
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experimental part
p. 3557 - 3563
(2011/11/06)
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- Synthesis and use of borane and platinum(II) complexes of 3-diphenylphosphino-1-phenylphospholane (LuPhos)
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3-Diphenylphosphinoyl-1-phenylphospholane 1-oxide (2) obtained by the Michael addition of diphenylphosphine oxide to the double-bond of 1-phenyl-2-phospholene 1-oxide (1) was subjected to double deoxygenation to afford the corresponding bisphosphine (3, LuPhos) that was converted to bis(phosphine borane) 4 and to cis chelate platinum(II) complex 6. A mixed phosphine oxide-phosphine borane 5 was also prepared. Stereostructures of the bidentate P-ligand 3 and the ring platinum(II) complex (6) were evaluated by quantum chemical calculations. Complex 6 used as a catalyst showed modest activity, but unusual regioselectivity in the hydroformylation of styrene and its 4-substituted analogues.
- Pietrusiewicz, K. Michal,Flis, Anna,Ujj, Viktoria,Koertvelyesi, Tamas,Drahos, Laszlo,Pongracz, Peter,Kollar, Laszlo,Keglevich, Gyoergy
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experimental part
p. 730 - 736
(2012/01/04)
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- O-acylation mechanism of p-substituted phenols with various alkanoyl chlorides under phase transfer catalysis conditions
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The phenolic ester synthesis between equimolecular amounts of phenols and various alkanoyl chlorides in the presence of aqueous sodium hydroxide solution in a two-phase system (20 mL of each 10% NaOH and dicloromethane, respectively) was reinvestigated under PTC conditions (10 mmol of tetrabutyl ammonium chloride, BNC). The esterification was complete within several minutes and the obtained ester was in high purity. For example, phenyl acetate was obtained quantitatively at 0°C in 5 minutes using a stoichiometric amount of BNC. This acylation procedure is technically simple and does not require anhydrous conditions. A bimolecular electrophilic attack of alkanoyl chloride against the ion-pair in the organic phase, which was formed between the quaternary ammonium cation and the phenoxide anion, must be a rate-determining step, because a plot of the logarithm of relative rate constants of various alkanoyl chlorides vs Taft's polar substituents constants (taking into account the steric constants, Es) gave a good linear relationship. We have found a simple, rapid, convenient, easily separating and efficient PTC technique to synthesize phenolic esters.
- Hashimoto, Iwao,Kawaji, Takatoshi,Mitoma, Yoshiharu,Simion, Alina M.,Semion, Cristian,Ishimoto, Keiko,Prakash, G.K. Surya,Olah, George A.,Tashiro, Masashi
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p. 149 - 155
(2007/10/03)
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- Refinement and evaluation of a pharmacophore model for flavone derivatives binding to the benzodiazepine site of the GABAA receptor
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To further develop and evaluate a pharmacophore model previously proposed by Cook and co-workers (Drug Des. Discovery 1995, 12, 193-248) for ligands binding to the benzodiazepine site of the GABAA receptor, 40 new flavone derivatives have been synthesized and their affinities for the benzodiazepine site have been determined. Two new regions of steric repulsive interactions between ligand and receptor have been characterized, and the receptor region in the vicinity of 6- and 3′-substituents has been mapped out. 2′-Hydroxy substitution is shown to give a significant increase in affinity, which is interpreted in terms of a novel hydrogen bond interaction with the previously proposed hydrogen bond-accepting site A2. On the basis of the results of these studies and the refined pharmacophore model, 5′-bromo-2′-hydroxy-6-methylflavone, the highest affinity flavone derivative reported so far (Ki = 0.9 nM), was successfully designed. A comparison of the pharmacophore model with a recently proposed alternative model (Marder; et al. Bioorg. Med. Chem., 2001, 9, 323-335) has been made.
- Kahnberg, Pia,Lager, Erik,Rosenberg, Celia,Schougaard, Jette,Camet, Linda,Sterner, Olov,Nielsen, Elsebet ?stergaard,Nielsen, Mogens,Liljefors, Tommy
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p. 4188 - 4201
(2007/10/03)
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- Sulfonamide-substituted chromans, processes for their preparation, their use as a medicament or diagnostic, and medicament comprising them
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Sulfonamide-substituted chromans, processes for their preparation, their use as a medicament or a diagnostic, and medicament comprising them Chromans of the formula I and of the formula 1a having the meanings R(A), R(B), R(C) and R(1) to R(8) indicated in the claims are outstandingly suitable for preparing a medicament for blocking the K+channel which is opened by cyclic adenosine monophosphate (cAMP); and further for preparing a medicament for inhibiting gastric acid secretion; for the treatment of ulcers of the stomach and of the intestinal region, in particular of the duodenum, for the treatment of reflux esophagitis, for the treatment of diarrheal illnesses, for the treatment and prevention of all types of arrhythmias including ventricular and supraventricular arrhythmias, and for the control of reentry arrhythmias and for the prevention of sudden heart death as a result of ventricular fibrillation.
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- Desilylation-acetylation of trimethylsilyl ethers with acetic anhydride catalysed by montmorillonite K-10
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Two mild and simple one-step desilylation-acetylations of a variety of alkyl- and aryl-trimethylsilyl ethers, Me3SiOR(Ar), with acetic anhydride in the presence of montmorillonite K-10 clay are described.
- Movassagh,Lakouraj,Fasihi
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p. 348 - 349
(2007/10/03)
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- Volatile components of the liverworts Archilejeunea olivacea, Cheilolejeunea imbricata and Leptolejeunea elliptica
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Three liverworts, Archilejeunea olivacea. Cheilolejeunea imbricata and Leptolejeunea elliptica, belonging to the Lejeuneaceae, have been investigated chemically. Olivacene, a new naturally occurring sesquiterpene hydrocarbon, β-monocyclonerolidol and (-)-spathulenol have been isolated from A. olivacea. The strong milky-like fragrance of C. imbricata is due to a mixture of (R)-dodec-2-en-1, 5-olide and (R)-tetradec-2-en-1,5-olide. Leptolejeunea elliptica produces an intensely fragrant odour which is due to a mixture of 1-ethyl-4-methoxy-, 1-ethyl-4-hydroxy- and 1-ethyl-4- acetoxybenene. There are no chemical affinities between the present three Lejeuneaceae species.
- Toyota, Masao,Koyama, Hiroki,Asakawa, Yoshinori
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p. 1261 - 1264
(2007/10/03)
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- Total Synthesis of (+/-)-cis-Trikentrin A
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Two patways towards the construction of the trikentrin skeleton are presented, one leading to the total synthesis of (+/-)-cis-Trikentrin A (1).The key step is the intramolecular Heck coupling of the triflate 21 to form the five-membered ring of the indenes 22 and 23.
- Wiedenau, Paul,Monse, Barbara,Blechert, Siegfried
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p. 1167 - 1176
(2007/10/02)
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- Substituent Effect in o-Nitroperbenzoic Acid Oxidation of m- and p-Substituted Acetophenones
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The Baeyer-Villiger reaction of m- and p-substituted acetophenones (substituents: H, p-MeO, p-t-Bu, p-i-Pr, p-Et, p-Me, p-Cl, p-Br, m-MeO, m-Me, m-Cl) with o-nitroperbenzoic acid was studied in chloroform at 30 deg C.The rate constants for the general acid catalysis were measured at several concentrations of o-nitrobenzoic acid which acted as an acid catalyst.The uncatalyzed and acid-catalyzed rate constants obtained afforded ρ values of -2.16 and -4.11 with ?, respectively.The results indicated that the rate-determining step is the migration of the phenyl group in the peroxy acid-carbonyl adduct for all the substituents studied, whether the reaction is acid-catalyzed or not, and that the acid catalyst intervenes only in the formation of the acid-ketone adduct in the initial state and not in the migration step.The variation of the leaving group abilities required the variation of the substituent constants applied, whereas the acid intervention in the addition step was reflected only in the variation of the ρ value, not in the substituent constants to be applied.The smaller resonance demand for o-nitrobenzoic acid indicated that the structure of the transition state in the migration step was looser and that the position of the transition state was earlier than those for m-chloroperbenzoic acid.
- Token, Katsuo,Hirano, Kenji,Yokoyama, Tai,Goto, Katsumi
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p. 2766 - 2771
(2007/10/02)
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- NEW SYNTHESIS OF 4-SUBSTITUTED CHROMANS FROM VINYLIC SULFOXIDES
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The condensation of vinylic sulfoxides with substituted o-acetylphenol followed by cyclization afforded in two high yield steps the corresponding 4-hydroxymethyl-2H-chromene, easily transformed into 4,4-dimethyl chroman.
- Solladie, Guy,Girardin, Andre
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p. 123 - 124
(2007/10/02)
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- A comparison of electron spin resonance α- and β-hyperfine coupling constants in para-substituted α-phenethyl radicals
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The linear relationship between the electron spin resonance hyperfine coupling constants (hfc) of the α- and β-hydrogens of para-substituted α-phenethyl radicals provides experimental evidence that the magnitude of both the α- and β-hfc is determined largely by the extent of spin delocalization in these benzylic systems.The ?α. scale, developed using substituted radicals, is shown to apply to phenethyl radicals as well.
- Arnold, Donald R.,Nicholas, A. Martin De P.,Young, Kent M.
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p. 769 - 772
(2007/10/02)
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