- Six- and eightfold palladium-catalyzed gross-coupling reactions of hexa- and octabromoarenes
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Palladium-catalyzed sixfold coupling of hexabromobenzene (20) with a variety of alkenylboronates and alkenylstannanes provided hexaalkenylbenzenes 1 in up to 73% and 16 to 41% yields, respectively. In some cases pentaalkenylbenzenes 21 were isolated as the main products (up to 75%). Some functionally substituted hexaalkenylbenzene derivatives containing oxygen or sulfur atoms in each of their six arms have also been prepared (16 to 24% yield). The sixfold coupling of the less sterically encumbered 2, 3, 6, 7, 10, 11-hexabromotriphenylene (24) gave the desired hexakis(3,3-dimethyl-1-butenyl) triphenylene (25) in 93% yield. The first successful cross-coupling reaction of octabromonaphthalene (26) gave octakis-(3,3-dimethyl-1-butenyl)naphthalene (27) in 21% yield. Crystal structure analyses disclose that, depending on the nature of the substituents, the six arms are positioned either all on the same side of the central benzene ring as in 1a and 1i, making them nicely cup-shaped molecules, or alternatingly above and below the central plane las in 1h and 23. In 27, the four arms at C-1, 4, 6, 7 are down, while the others are up, or vice versa. Upon catalytic hydrogenation, 1a yielded 89% of hexakis(tert-butylethyl)benzene (23). Some efficient accesses to alkynes with sterically demanding substituents are also described. Elimination of phosphoric acid from the enol phosphate derived from the corresponding methyl ketones gave 1-ethynyladamantane (3b, 62% yield), 1-ethynyl-1-methylcyclohexane (3c, 85%) and 3,3-dimethylpentyne (3e, 65%). 1-(Trimethylsilyl)ethynylcyclopropane (7) was used to prepare 1-ethynyl-1-methylcyclopropane (3d) (two steps, 64% overall yield). The functionally substituted alkynes 3 f-h were synthesized in multistep sequences starting from the propargyl chloride 11, which was prepared in high yields from the dimethylpropargyl alcohol 10 (94%). The alkenylstannanes 19 were prepared by hydrostannation of the corresponding alkynes in moderate to high yields (42-97%), and the alkenylboronates 2 and 4 by hydroboration with catecholborane (27-96% yield) or pinacolborane (26-69% yield).
- Stulgies, Balder,Prinz, Peter,Magull, Joerg,Rauch, Karsten,Meindl, Kathrin,Ruehl, Stephan,De Meijere, Armin
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Read Online
- VISCOSOL, A C-3' PRENYLATED FLAVONOID FROM DODONAEA VISCOSA
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The structure of viscosol, a new prenylated flavonoid isolated from the aerial parts of Dodonaea viscosa, was established on the basis of spectral studies as well as by the conversion of the flavonol penduletin into permethyl viscosol.
- Sachdev, Kusum,Kulshreshtha, Dinesh K.
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Read Online
- SYP-5, a novel HIF-1 inhibitor, suppresses tumor cells invasion and angiogenesis
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Hypoxia-inducible factor-1 (HIF-1) plays an essential role in carcinogenesis. The overexpression of HIF-1 induced by hypoxia is closely associated with metastasis, poor prognosis and high mortality. In this study, a novel HIF-1 inhibitor SYP-5 was first observed by the luciferase reporter assay. Western blots results showed SYP-5 inhibited hypoxia-induced upregulation of HIF-1. Moreover, the proteins of vascular endothelial growth factor (VEGF) and matrix metalloproteinases (MMP)-2 that are targets of HIF-1, were down-regulated by SYP-5. Furthermore, in the tube formation assay, SYP-5 suppressed angiogenesis induced by hypoxia and VEGF in vitro. Additionally, using Transwell and RTCA assays, we found that SYP-5 also retarded the Hep3B and Bcap37 cells migration and invasion induced by hypoxia and FBS. Last, we also detected the upstream pathways related to HIF-1 and found both PI3K/AKT and MAPK/ERK were involved in the SYP-5 mediated invasive inhibition of Bcap37 cells. These results indicates that SYP-5 inhibits tumor cell migration and invasion, as well as tumor angiogenesis, which are mediated by suppressing PI3K/AKT- and MAPK/ERK-dependent HIF-1 pathway. It suggests that SYP-5 might be a potential HIF-1 inhibitor as an anticancer agent.
- Wang, Li-Hui,Jiang, Xiao-Rui,Yang, Jing-Yu,Bao, Xue-Fei,Chen, Jun-Li,Liu, Xing,Chen, Guo-Liang,Wu, Chun-Fu
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Read Online
- Asymmetric epoxidation of chromenes mediated by iminium salts: Synthesis of mollugin and (3S,4R)-trans-3,4-dihydroxy-3,4-dihydromollugin
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Organocatalytic asymmetric epoxidation of chromenes mediated by iminium salt catalysts under non-aqueous conditions provided ees as high as 99%. Contrastingly, reaction under aqueous conditions can form the corresponding diol products with ees as high as 71%. The process has been used for the synthesis of the East African medicinal plant metabolite (3S,4R)-trans-3,4-dihydroxy-3,4-dihydromollugin.
- Bulman Page, Philip C.,Chan, Yohan,Noor Armylisas, Abu Hassan,Alahmdi, Mohammed
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Read Online
- Comparative reactivity of hydroxyketones and their derivatives in the reactions with N,S-nucleophiles
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The reactions of thiosemicarbazide (TSC), thiocarbohydrazide, and hydrazine thiocarbamate with oxyketones, haloketones, and derivatives of acetylenic alcohols were studied. Thiadiazines bearing exocyclic thio and hydrazo groups were synthesized. Acetylenic alcohols react with TSC to give the corresponding thiazolidines. The reactions of halo derivatives of acetylenic alcohols with TSC are complicated by side reactions.
- Abdullaev, T. Kh.,Isobaev, M. D.,Mavlonov, B. G.,Pulatov, E. Kh.
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Read Online
- Enantioselective epoxidation of dihydroquinolines by using iminium salt organocatalysts
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The first examples of asymmetric epoxidation of dihydroquinoline substrates using iminium salt organocatalysts are reported. The 3,4-epoxytetrahydroquinoline products are obtained in good yields and with moderate to good enantioselectivities.
- Page, Philip C. Bulman,Day, David P.,Chan, Yohan
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Read Online
- Natural product-inspired rational design, synthesis and biological evaluation of 2,3-dihydropyrano[2,3-f]chromen-4(8H)-one based hybrids as potential mitochondrial apoptosis inducers
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Synthesis of novel pyranochromanone amide hybrids, by combining pyranochromanone pharmacophore and privileged scaffolds such as 2-amino-1,3,4-thiadiaole/2-aminothiazole/aminopyridine/aminonaphthalene and anti-cancer evaluation of a series led us to discover a series of new chemical entities (NCEs) showing broad spectrum of anti-cancer activity against three different human cancer cell lines (MCF-7, A549 and HeLa), at IC50values ranging from 14.3 to 97.8?μM. Among them, some compounds such as 15b, 15d, 20a and 20b displayed excellent activity against breast cancer cell line MCF-7. Detailed biological studies such as AO/EB dual staining, Hoechst 33342 staining, FACS analysis of mitochondrial membrane potential (Δψm) using JC-1 dye and DNA fragmentation confirmed the apoptosis induced by the hybrids. Gene expression studies by Real time RT-PCR has shown that these compounds are efficient regulator of anti-apoptotic gene Bcl-2. Western blot analysis also revealed that these compounds persuade apoptosis through intrinsic pathway by up-regulating the pro-apoptotic protein Bax and down-regulating the anti-apoptotic protein Bcl-2. Molecular docking studies reveal that compounds 15b and 20b binds efficiently with Bcl-2 promoter G-quadruplex.
- Sakthivel, Palaniappan,Ilangovan, Andivelu,Kaushik, Mahabir Prasad
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Read Online
- Calix[n] arenes mediated phase-transfer catalytic synthesis of purine derivatives
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A new route was designed to achieve the synthesis of purine derivatives under phase-transfer catalysis conditions using calix[n]arenes TACnA (n = 4, 6, and 8) as phase-transfer catalyst for the first time in this particular type of synthesis. The compounds were synthesized in excellent yields (70%-80%) and the structures were established on the basis of consistent IR, 1H NMR, FAB-Mass, and elemental analyses data. Their purity has been ascertained by chromatographic resolution using acetonitrile, methanol, and water (50:30:20, v/v) as eluenting system. Moreover, the kinetics of the reaction was studied and it was found to obey first-order kinetics. Effect of various parameters, namely, temperature, amount of catalyst, stirring speed, and so on was also investigated.
- Sharma, Pratibha,Kumar, Ashok,Sahu, Vinita,Singh, Jitendra
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Read Online
- Process for preparing 3-chloro-3-methylbutyne by usingsophthalic acid acylating chlorination byproduct hydrogen chloride gas
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The invention discloses a production process for preparing 3-chloro-3-methylbutyne by using an isophthalic acid acylating chlorination byproduct hydrogen chloride gas, which basically comprises the following steps: putting quantitative trichloromethyl benzene, isophthalic acid and a catalyst into an acylation reaction kettle, and simultaneously putting hydrochloric acid with a certain concentration, a catalyst and 3-methyl butyn-3-ol into a chlorination kettle; slowly raising the temperature of the acylation kettle to the reaction temperature, controlling the temperature of the chlorination kettle to be within a specified temperature range, and slowly dropwise adding the rest trichloromethyl benzene after the temperature of the acylation kettle is stable; subjecting the acylation byproduct hydrogen chloride gas to washing and impurity removal by a hydrochloric acid tower and deep cooling and water removal, and then introducing the treated hydrogen chloride gas into the chlorination kettle for chlorination of 3-methyl butyn-3-ol to prepare 3-chloro-3-methylbutyne, and returning deep cooling condensate to a hydrochloric acid washing tower; and after hydrochloric acid in the hydrochloric acid washing tower is recycled for a certain batch, conducting suction filtration, tap water washing and drying to obtain a small amount of byproduct benzoic acid.
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Paragraph 0022-0027
(2021/05/12)
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- A mild method for the replacement of a hydroxyl group by halogen: 3. the dichotomous behavior of α-haloenamines towards allylic and propargylic alcohols
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A study of the deoxyhalogenation of allylic and propargylic alcohols with tetramethyl-α-halo-enamines is reported. Primary allylic and primary and secondary propargylic alcohols gave the corresponding halides in high yields. Secondary allylic and propargylic alcohols yielded the corresponding secondary halides but the reaction also produced some rearranged primary halides (I > Br > Cl). The reactions with tertiary allylic and tertiary propargylic alcohols gave several products and was therefore of little synthetic value. However, the addition of triethylamine to the reaction mixture or the use of lithium alkoxide instead of alcohol brought about a major change of the course of the reaction which led to amides carrying an allyl or an allenyl group at C2. This was shown to result from a Claisen-Eschenmoser rearrangement of an intermediate α-allyloxy- or propargyloxy-enamine.
- Munyemana, Fran?ois,Patiny, Luc,Ghosez, Léon
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- Synthesis and biological evaluation of 2,2-dimethylbenzopyran derivatives as potent neuroprotection agents
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The development of novel neuroprotection agents is of great significance for the treatment of ischemic stroke. In this study, a series of compounds comprising 2,2-dimethylbenzopyran groups and cinnamic acid groups have been synthesized. Preferential combination principles and bioisostere that improved the neuroprotective effect of the compounds were identified for this series via biological activity assay in vitro. Meanwhile, a functional reversal group of the acrylamide amide resulted in the most active compounds. Among them, BN-07 significantly improved the morphology of neurons and obviously increased cell survival rate of primary neurons induced by oxygen glucose deprivation (OGD), superior to clinically used anti-ischemic stroke drug edaravone (Eda). Overall, our findings may provide an alternative strategy for the design of novel anti-ischemic stroke agents with more potency than Eda.
- Du, Fangyu,Zhou, Qifan,Fu, Xiaoxiao,Shi, Yajie,Chen, Yuanguang,Fang, Wuhong,Yang, Jingyu,Chen, Guoliang
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p. 2498 - 2508
(2019/02/01)
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- PROCESS FOR PREPARING AMINOTHIOL ESTER COMPOUNDS AND SALTS THEREOF
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A process for preparing aminothiol ester compounds and salts thereof. The present invention relates to a process for preparing compounds of formula (I), (I) comprising the following steps: a) reacting a compound of formula (II) with an inorganic acid or an organic acid, (II) b) reacting the compound obtained in step a) with a base; c) reacting the compound obtained in step b) with CO2; d) reacting the compound obtained in step c) with an alkyl chloroformate, a reagent capable of forming, with the compound obtained in step c), an acid halide, or a reagent capable of forming, with the compound obtained in step c), a mixed anhydride; e) reacting the compound obtained in step d) with an SMe anion precursor compound.
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Paragraph 0074; 0076-0077
(2019/02/24)
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- Preparation method for propyzamide
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The invention discloses a preparation method for propyzamide. The preparation method comprises the following steps: preparing 3-chloro-3-methylbutyne through a chlorination reaction; then preparing 3-amino-3-methylbutyne through an aminolysis reaction; and then carrying out an amidation reaction so as to prepare high-purity propyzamide. The optimal preparation method for propyzamide is screened out through a large number of experiments; the preparation method is reasonable in the whole process design and simple and efficient in process operation; in particular, optimal reaction conditions arescreened out, optimal raw material composition is determined for the chlorination reaction in the step 1, the aminolysis reaction in the step 2 and the amidation reaction in the step 3, and the proportions of reaction raw materials, reaction temperature, reaction time and the like are optimized, so reaction yield can be greatly increased (wherein the yield can reach 93% or more), side reactions can be reduced, reaction rate can be increased, and production cost can be greatly lowered; so the preparation method has good application prospects.
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Paragraph 0007-0008; 0036-0040; 0054; 0058
(2018/05/01)
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- 2,2-dimethylbenzopyran derivative and preparation method and use thereof
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The invention belongs to the technical field of medicines, and discloses a 2,2-dimethylbenzopyran derivative and a preparation method and use of the 2,2-dimethylbenzopyran derivative. The derivative and pharmaceutically acceptable salt of the derivative have the structural formulae shown in the description, wherein Ar, Ar, X, Y and R1 are as described in the claims and the description. The preparation methods of the derivative and the pharmaceutically acceptable salt of the derivative comprise the following steps: the formula (I) is obtained by mainly taking acetaminophen as a raw material, and subjected to the reactions of Williamson ether formation, cyclization, hydrolysis, amide formation and the like; the formula II is obtained by mainly taking p-hydroxybenzaldehyde as a raw material, and subjected to the reactions of the Williamson ether formation, cyclization, Knoevenagel condensation, amide formation and the like. The derivative and the pharmaceutically acceptable salt ofthe derivative disclosed by the invention can be used for preparing neuroprotective agents and have better neuroprotective effects on ischemic stroke.
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Page/Page column 11; 12
(2019/01/16)
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- A method for preparing alkyne benzoyl grass amine (by machine translation)
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The present invention provides a method for preparing alkyne benzoyl grass amine, comprising a condensation step: by parts by mass to 3 - amino - 3 - methyl [...] 100 - 105 parts, triethylamine 2 - 5 parts and solvent 100 - 500 parts into 10% -32% ω of sodium hydroxide solution 200 - 400 parts by, after stir, dropping 3, 5 - dichloro benzoyl chloride 100 - 105 parts, temperature control in 12 - 15 °C, after dropping, thermal insulation 1 - 5 hours. The alkyne benzoyl grass amine preparation method of the advantage of high purity of the product. (by machine translation)
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Paragraph 0019; 0020; 0022
(2018/04/01)
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- Light-induced stereospecific intramolecular [2+2]-cycloaddition of atropisomeric 3,4-dihydro-2-pyridones
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Atropisomeric 3,4-dihydro-2-pyridones undergo stereospecific [2+2]-photocycloaddition in solution with high stereoselectivity (ee > 98% and de > 96%) in the product. The chiral transfer during phototransformation was rationalized based on the stability/reactivity of the biradical.
- Kumarasamy, Elango,Sivaguru
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supporting information
p. 4346 - 4348
(2013/06/27)
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- Synthesis and exploration of QSAR model of 2-methyl-3-[2-(2-methylprop-1- en-1-yl)-1H-benzimidazol-1-yl]pyrimido[1,2-a]benzimidazol-4(3H)-one as potential antibacterial agents
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Present communication deals with the synthesis of novel 2-methyl-3-[2-(2-methylprop-1-en-1-yl)-1H-benzimidazol-1-yl]pyrimido[1,2-a] benzimidazol-4(3H)-one derivatives under phase transfer catalysis (PTC) conditions using benzyl triethyl ammonium chloride (BTEAC) as PTC. It also elicits the studies on in vitro antimicrobial evaluation of synthesized compounds against a representative genera of gram-negative and gram-positive bacteria i.e., Bacillus subtilis, Staphylococcus aureus, Pseudomonas diminuta and Escherichia coli. All the compounds have been found to manifest profound antimicrobial activity. Moreover, extensive quantitative structure-activity relationship (QSAR) studies have been performed to deduce a correlation between molecular descriptors under consideration and the elicited biological activity. A tri-parametric QSAR model has been generated upon rigorous statistical treatment.
- Sharma, Pratibha,Kumar, Ashok,Sharma, Manisha,Singh, Jitendra,Bandyopadhyay, Prabal,Sathe, Manisha,Kaushik
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scheme or table
p. 294 - 301
(2012/07/01)
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- Synthesis of functionalized polycyclic compounds: Rhodium(I)-catalyzed intramolecular cycloaddition of yne and ene vinylidenecyclopropanes
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Three ring circus: The title reaction can efficiently provide functionalized polycyclic compounds containing cyclobutene (see scheme; PG=protecting group) or aza-cyclooctene moieties in a highly regio- and diastereoselective manner with moderate to good yields under mild reaction conditions. The scope and limitations are disclosed and plausible reaction mechanisms are discussed. Copyright
- Lu, Bei-Li,Shi, Min
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supporting information; experimental part
p. 12027 - 12031
(2012/02/03)
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- Palladium-mediated intramolecular C-N bond formation involving allyl substituted pyridines. Application to a novel strategy for the synthesis of the skeleton of berberinium derivatives
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The insertion of allenes in the Pd-C σ bond of cyclopalladated pyridine derivatives afforded (η3-allyl) Pd complexes. The ideally located imine unit reacted selectively with the allyl functionality to yield a series of new cationic heterocycles. The process opened the route to a novel strategy for the synthesis of berberiniums, a class of molecules of pharmacological interest.
- Chengebroyen, Jaganaiden,Linke, Myriam,Robitzer, Mike,Sirlin, Claude,Pfeffer, Michel
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p. 313 - 321
(2007/10/03)
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- Total synthesis of seco-lateriflorone
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A convergent strategy toward the synthesis of lateriflorone (5) is described. Our approach is based on biosynthetic considerations and draws on a sequence of prenylation, oxygenation and Claisen reactions for the construction of chromenequinone 6, and a tandem Claisen/Diels-Alder reaction cascade for the synthesis of caged tricycle 7. Union of fragments 6 and 7 led to the synthesis of seco-lateriflorone (49).
- Tisdale, Eric J.,Vong, Binh G.,Li, Hongmei,Kim, Sun Hee,Chowdhury, Chinmay,Theodorakis, Emmanuel A.
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p. 6873 - 6887
(2007/10/03)
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- The Heterogeneous Catalytic Hydrogenation of Cumulated Allene-cyclopropanes: 1-(2'-Methylpropenylidene)-7-bicycloheptane
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The formation of products from the heterogeneous solution phase catalytic hydrogenation of the title compound 1 in methanol over supported platinum and palladium catalysts has been studied using 'snapshot analysis' graphs. As expected from 'catalyst hindrance' considerations, the major first formed product with both metals is the conjugated cis-olefin-cyclopropane 7, the trans-isomer 8 being made for comparison by sodium in liquid ammonia reduction. Products appear and disappear during the hydrogenations leaving, at the cassation of reaction in the case of platinum catalyst, 75 percent of cyclopropane 6 and 25 percent of saturated hydrocarbon 3. Use of a palladium reverses the quantitative situation - 12 percent cyclopropane 6 and 88 percent of hydrocarbon 3. If in the title allene-cyclopropane structure 1 a methyl is inserted at position 1 of the cyclopropyl as in 13, complete hydrogenation over a palladium catalyst occurs with cleavage of the cyclopropane from the less hindered side forming a quaternary centre 14 in high yield. Catalytic hydrogenation of a related conjugated diene having one double bond cumulated with a cyclopropane ring 12 is also considered. Dimethylallene carbene reacts selectively towards an (E)-linkage of (Z)-(E)-(E)-cyclododeca-1,5,9-triene giving 19 as the crystalline product.
- Cromble, Leslie,Fernando, Candida E. C.
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p. 1501 - 1518
(2007/10/03)
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- Phosphinic ester substituted benzopyran derivatives
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STR1 and pharmaceutically acceptable salts thereof wherein Y is a single bond, --CH 2 --, --C(O)--, --S-- or --N(R 11)--; and R 1 to R 6 are as defined herein. These compounds have potassium channel activating activity and are useful, therefore for example, as cardiovascular agents.
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- Synthesis of [12-3H]-(±)-calanolide A
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[12-3H]-(±)-Calanolide A (9) was synthesized in five steps from readily available phloroglucinol (1). Stereoselective Luche reduction of transketone 8 with cerium(III) chloride and sodium borotritide in methanol gave 338 μCi of 9 with a specific activity of 63.0 mCi/mmol.
- Rehder, Ken S.,Hristova-Kazmierski, Maria K.,Kepler, John A.
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p. 1077 - 1081
(2007/10/03)
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- Indane and quinoline derivatives
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Novel indane and quinoline derivatives, useful, for example, as antiischemic agents, having the formula STR1 where A, X, R1 -R7 are as defined herein, are disclosed.
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- The Preparation and Lithiation of 1-Halogenocyclopropenes
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Reaction of a range of 1,1,2-trihalogenocyclopropanes (halogen = bromine, chlorine) with methyl-lithium in ether at -90 - 20 deg C leads to 1,2-dehalogenation to the corresponding 1-halogenocyclopropene.The halogenocyclopropenes are readily lithiated by lithium-halogen exchange with a second equivalent of methyl-lithium to give 1-lithiocyclopropenes, which are in turn trapped by electrophiles; an exception to this is compound (21; X = Cl), which leads to 3-methylbuta-1,2-dienylidene (31) by initial lithium-hydrogen exchange and loss of lithium chloride.The cyclopropenes (5; R = Me, X = Br or Cl) and (21; X = Br or Cl) decompose even at temperatures around ambient, leading either to enynes (6; R = Me) or halogenoalkynes (18; X = Br or Cl).A 12C-labelling study indicates that C-1 of the cyclopropene (21; X = Cl) becomes C-2 of the alkyne (18; X = Cl) on rearrangement.
- Baird, Mark S.,Hussain, Helmi H.,Nethercott, William
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p. 1845 - 1854
(2007/10/02)
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- SYNTHESIS OF (+/-)DEHYDROXYGLAUPALOL AND ANALOGS
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The natural furocoumarin dehydroxyglaupalol and two analogs were prepared by reaction of the appropriate 4-hydroxycoumarin with 3-chloro-3-methylbutyne in basic medium, followed by catalytic hydrogenation of the exo double bond.
- Chenevert, Robert,Page, Jocelyne,Voyer, Normand
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p. 737 - 742
(2007/10/02)
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- A homoallyl radical rearrangement. Kinetics of the isomerization of the 2,2-dimethyl-3-buten-1-yl radical to the 1,1-dimethyl-3-buten-1-yl radical
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Rate constants for the overall rearrangement of the 2,2-dimethyl-3-buten-1-yl radical to the 1,1-dimethyl-3-buten-1-yl radical, kC=C, have been measured from -145 deg C to -101 deg C by kinetic epr specroscopy and at 40 deg C by spin trapping with 1-methyl-4-nitroso-3,5-diphenylpyrazole.The temperature dependence can be represented by log(kC=C/s-1)=(12.5+/-0.6)-(6.6+/-0.4)/θ where θ=2.3RT kcal mol-1.This rearrangement, which must proceed via a 2,2-dimethylcyclopropylcarbinyl radical as an intermediate, is one of the fastest rearrangements involving a primary alkyl radical.At 25 deg C, kC=C=4,3*107s-1, which makes this rearrangement aaabout 10000 times faster than the rearrangement of the simplest homoallyl radical, 3-buten-1-yl.This rate enhancement is attributed to steric acceleration of ring closure by the gem dimethyl groups (Thorpe-Ingold effect).
- Chatgilialoglu, Chryssostomos,Ingold, Keith U.
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p. 1077 - 1081
(2007/10/02)
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- Cycloaddition Reactions of Allenyl Cations with Cyclopentadiene
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Propargyl halides R1-C=-C-CR2R3X (14) and cyclopentadiene react with zinc halide catalysis in ether/dichloromethane solution to give 3-halogenobicycloocta-2,6-dienes 13 (R1 = alkyl) or 5-(α-halogenobenzylidene)norbornenes 15 (R1 = aryl).The reactions are interpreted by stepwise - and -cycloadditions of intermediate allenyl cations 1, proceeding via propargylcyclopentenyl cations 5 and bicyclic vinyl cations 9 or 12.If the reactions are initiated by equimolar amounts of silver trifluoroacetate, quenching products of all postulated intermediates are isolated.The relative energies of the intermediate carbenium ions are estimated on the basis of force field calculations and of gas phase stabilities of simple carbocations.Stereochemical studies indicate that the addition reactions proceed via the compact transition state 42 rather than 41.The zinc chloride catalysed reaction of propargyl chloride 14e with cyclopentadiene yields the 2:1 product 17 (structurally assigned by X ray analysis) in addition to the 1:1 product 15e.The formation of 17 is rationalised by a -cycloaddition of allenyl cation 1 with cyclopentadiene.
- Mayr, Herbert,Halberstadt-Kausch, Inge K.
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p. 3479 - 3515
(2007/10/02)
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- Reactions of Hydrogen Chloride with 3-Methyl-1-butyne: Cycloaddition and Rearrangement Reactions via Vinyl Cations
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3-Methyl-1-butyne was reacted with anhydrous hydrogen chloride in the liquid phase at ambient temperatures.A total of 12 products were identified: three monoadducts (4, 6, 9), three diadducts (5, 7, 10), one substitution product (8), as well as five cycloaddition products having cyclobutane structures (11-15).Model reactions provided evidence for the mode of formation of the reaction products.
- Stammann, Guenter,Griesbaum, Karl
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p. 598 - 606
(2007/10/02)
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- Preparation of a Series of Highly Hindered Secondary Amines, Including Bis(triethylcarbinyl)amine
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A series of highly branched secondary amines was prepared by coupling propargylamines with propargyl chlorides.Hydrogenation of the resultant dipropargylamines was accomplished with Raney nickel in the presence of potassium hydroxide.The resultant amines, including bis(triethylcarbinyl)amine, are among the most hindered secondary amines reported to date.The pKa values of the conjugate acids of the series of secondary amines exhibit a regular decrease with increasing size of the amine.The bulkier members of the series are inert to methyl iodide.Bis(triethylcarbinyl)amine reacts with boron trifluoride etherate to give a primary amine adduct and 3-ethyl-2-pentene.
- Kopka, Ihor E.,Fataftah, Zacharia A.,Rathke, Michael W.
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p. 4616 - 4622
(2007/10/02)
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- Studies in the Xanthone Series. Part 13. Structural and Synthetic Studies on Toxyloxanthone B
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A re-consideration of the 1H n.m.r. data for toxyloxanthone B trimethyl ether and an unambiguous total synthesis both show that toxyloxanthone B has the 1,1-dimethylpyranoxanthone structure (1a) and not the 3,3-dimethylpyranoxanthone system (2) previously assigned.The synthesis is based on the preparation of 1,7-dihydroxy-3,5-dimethoxyxanthone (5) from cyclisation of a benzophenone precursor (3a) or (3b) and selective demethylations.A Claisen rearrangement of the 7-prop-2-ynyloxyxanthone (6) followed by cyclisation and methylation gives toxyloxanthone B trimethyl ether.
- Cotterill, Phillip J.,Scheinmann, Feodor
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p. 2353 - 2357
(2007/10/02)
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- Reactions of 3-Chloro-3-methyl-1-butyne with Hydrogen Chloride: Evidence Against an Electrophilic Addition Reaction
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Reactions of 3-chloro-3-methyl-1-butyne (1) with an excess of anhydrous hydrogen chloride in the liquid phase afforded approx. 16 products.Major product was 1,1,3-trichloro-3-methylbutane (6).In addition, (E)-1,3-dichloro-3-methyl-1-butene (5) and (Z)- and (E)-1,3-dichloro-2-methyl-2-butene (11a, b) were formed in considerable amounts.The expected products of an electrophilic addition to the triple bond, however, were only found in very minute amounts.The formation of the products obtained was rationalized by heterolysis of the C-Cl bond in the substrate 1 and subsequent reactions of the ensuing intermediate mesomeric cation A.
- Stammann, Guenter,Rehman, Zillur,Griesbaum, Karl
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p. 3103 - 3111
(2007/10/02)
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