- A Selective and Functional Group-Tolerant Ruthenium-Catalyzed Olefin Metathesis/Transfer Hydrogenation Tandem Sequence Using Formic Acid as Hydrogen Source
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A ruthenium-catalyzed transfer hydrogenation of olefins utilizing formic acid as a hydrogen donor is described. The application of commercially available alkylidene ruthenium complexes opens access to attractive C(sp3)-C(sp3) bond formation in an olefin metathesis/transfer hydrogenation sequence under tandem catalysis conditions. High chemoselectivity of the developed methodology provides a remarkable synthetic tool for the reduction of various functionalized alkenes under mild reaction conditions. The developed methodology is applied for the formal synthesis of the drugs pentoxyverine and bencyclane.
- Zieliński, Grzegorz K.,Majtczak, Jaros?awa,Gutowski, Maciej,Grela, Karol
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p. 2542 - 2553
(2018/03/09)
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- A 2 - (2-allyl) pentene-4-acid methyl ester preparation method (by machine translation)
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The invention relates to a machine intermediate 2 - (2-allyl) pentene-4-acid methyl ester preparation method, the preparation method is as follows: step 1) malonic acid ring (inferior) of potassium hydroxide in isopropyl acetate under alkaline conditions by PEG-400 catalytic and 3-polybromide propylene reaction produce compound 1 ; step 2) compound 1 under alkaline conditions in the sodium hydroxide of hydrolyzed to generate β-b acid compound 2 ; step 3) β-b acid compound 2 is heated and a single carboxyl the carboxyl group lives 3 ; step 4) single carboxyl compound 3 is obtained by reacting the methyl ester of the methyl esterification of compound 4 ; step 5) methyl ester compound 4 under alkaline conditions in and again LDA 3-polybromide propylene reaction produce the target compound 5. In the method for preparing the raw materials of the malonic acid ring a (sub) and isopropyl acetate 3-polybromide propylene, low cost, small synthetic process step, the operation is simple, convenient extraction and purification, the yield can reach 80% or more. (by machine translation)
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Paragraph 0016; 0019
(2017/03/14)
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- In tandem or alone: A remarkably selective transfer hydrogenation of alkenes catalyzed by ruthenium olefin metathesis catalysts
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A system for transfer hydrogenation of alkenes, composed of a ruthenium metathesis catalyst and HCOOH, is presented. This operationally simple system can be formed directly after a metathesis reaction to effect hydrogenation of the metathesis product in a single-pot. These hydrogenation conditions are applicable to a wide range of alkenes and offer remarkable selectivity. This journal is
- Zieliski, Grzegorz Krzysztof,Samojlowicz, Cezary,Wdowik, Tomasz,Grela, Karol
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supporting information
p. 2684 - 2688
(2015/04/14)
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- Oxidative rearrangement of malondialdehyde: Substrate scope and mechanistic insights
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A novel oxidative rearrangement of malondialdehyde was described. Under the effect of H2O2, malondialdehyde smoothly transferred to carboxylic acid with C-C bond cleavage in good to excellent yields. Mechanistic studies showed that this reaction proceeded via the formation of a 1,2-dioxolane intermediate, followed by concert C-C, O-O, C-H bond cleavage and a hydride shift.
- Yu, Xin,Liu, Zheng,Xia, Zilei,Shen, Zhigao,Pan, Xixian,Zhang, Hui,Xie, Weiqing
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p. 53397 - 53401
(2015/01/16)
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- Use of ethyl (benzothiazol-2-ylsulfonyl)acetate for malonic ester-type syntheses of carboxylic acids and esters
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A new methodology for the synthesis of substituted carboxylic acids is described. Alkylation of either ethyl (benzothiazol-2-ylsulfonyl)acetate or ethyl 2-(benzothiazol-2-ylsulfonyl)propionate was achieved with alkyl halides and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in dichloromethane solution. These products were then desulfinated and hydrolysed in one-pot under mild conditions to give substituted acetic acids in good-to-excellent yields.
- Hussein, Waleed M.,McGeary, Ross P.
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p. 1222 - 1227
(2014/10/16)
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- Study on the total synthesis of velbanamine: Chemoselective dioxygenation of alkenes with PIFA via a stop-and-flow strategy
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A "stop-and-flow" strategy was developed for the chemoselective dioxygenation of alkenes with a PIFA-initiated cyclization. This method is conceived for the desymmetrization of seco-diene, and a series of substituted 5-hydroxymethyl-γ-lactones were constructed after hydrolysis. This strategy also differentiates terminally substituted alkenes and constitutes a potentially novel synthetic approach for the efficient synthesis toward velbanamine.
- Liu, Huili,Zheng, Kuan,Lu, Xiang,Wang, Xiaoxia,Hong, Ran
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supporting information
p. 983 - 990
(2013/07/19)
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- Metal-free oxyaminations of alkenes using hydroxamic acids
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A radical-mediated approach to metal-free alkene oxyamination is described. This method capitalizes on the unique reactivity of the amidoxyl radical in alkene additions to furnish a general difunctionalization using simple diisopropyl azodicarboxylate (DIAD) as a radical trap. This protocol capitalizes on the intramolecular nature of the process, providing single regioisomers in all cases. Difunctionalizations of cyclic alkenes provide trans oxyamination products inaccessible using current methods with high levels of stereoselectivity, complementing cis-selective oxyamination processes.
- Schmidt, Valerie A.,Alexanian, Erik J.
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supporting information; experimental part
p. 11402 - 11405
(2011/09/16)
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- Metal-free, aerobic dioxygenation of alkenes using hydroxamic acids
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(Chemical equation presented) One dioxygenation please, hold the metal: In the presence of either oxygen or air as the sole oxidant and external oxygen atom source, a variety of unsaturated hydroxamic acids afford cyclic hydroxamates that are readily converted into 1,2-diols, with the potential for high levels of reaction stereocontrol.
- Schmidt, Valerie A.,Alexanian, Erik J.
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supporting information; experimental part
p. 4491 - 4494
(2010/08/21)
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- Insights into the formation of symmetrical trimers of dialkylated ketenes starting from acid chloride precursors
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Application of known dialkyl ketene di- and trimerization to more complex precursors could readily open the route to highly functionalized symmetrical cyclobuta-1,3-diones and cyclohexa-1,3,5-triones. We report herein the results on three substrates containing either a C=C double bond or a protected glycol moiety as illustrative functionalized groups. The nature of the substituents is found to be crucial: while cyclopentenyl and more constrained dioxolanocyclopentenyl precursors efficiently dimerize, a diallylic derivative fails. At the millimolar scale, methoxide-catalyzed trimerization shows limited reproducibility, even for the reported substrate tetramethylcyclobuta-1,3-dione. However, systematic studies, including the use of microwaves, demonstrate that formation of symmetrical trimers is favored under solvent-free conditions and conventional heating, which allowed us to isolate and characterize trispiro[4.1.4.1.4.1]octadeca-2,9,15-triene-6,12,18-trione.
- Saaidi, Pierre-Loic,Doridot, Gabriel,Jeanneau, Erwann,Hasserodt, Jens
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p. 1011 - 1018
(2008/03/17)
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- Reactions of 2-(perfluoroalkyl)ethane thiols with 1,6-heptadiene and 4-substituted 1,6-heptadienes: The synthesis of RFethanethio- cyclopentanoic and -dioic acids; and, "geminal-twin-tail" bis-(perfluoroalkylethanethio)alkanoic acids
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Kinetic analysis of the free radical addition of n-C6F 13I to 1,6-heptadiene gives a rate ratio of cyclization to addition (kd1/kc) of 0.568 at 70°C; thus, the rate of cyclization (kc) is twice that of iodine transfer (kd1). By contrast, for n-C6F13CH2CH2SH (kd1/kc) = 14.4 at 70°C, and radical transfer of H from the thiol is 14.4 times the faster than cyclization. Substitution at the center of 1,6-heptadiene has a profound effect on the linear/cyclic adduct ratio. For the addition of n-C3F7I (RFI:diene= 2:0) the adduct ratios dramatically decrease in the order: 1,6-heptadiene (1.17) > 4-carboxy-1,6-heptadiene (0.0613) > 4,4-bis-ethoxycarbonyl-1,6- heptadiene (F(CH 2)3]2CHCO2R, or [R F(CH2)3]2C(CO2R) 2 must be synthesized by other means. For the reaction of R FCH2CH2SH with the dienes (1:1), the respective adduct ratios are 11.3 (n-C6F13), 0.370 (n-C 8F17), and 0.0716 (n-C6F13). However, adding the 4-carboxy-1,6-heptadiene slowly to four mols of n-C 8F17CH2CH2SH yields 98% of the geminal bis-adduct [RFCH2CH2S(CH 2)3]2CHCO2H, which is a new, fluorophilic, geminal-twin-tail acid.
- Brace, Neal O.
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- Syntheses of 4-[(1H,3H)-pyrimidine-2,4-dion-1-yl]- and 4-[(1H,3H)-5- methylpyrimidine-2,4-dion-1-yl]-1,6-heptadienes
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Heptadienes containing nucleic bases are attractive building blocks for the synthesis of carbocyclic oligonucleotide analogs. Herein, we report an alternative synthetic route to 4-[(1H,3H)-pyrimidine-2,4-dion-1-yl]-1,6- heptadiene and 4-[(1H,3H)-5-methylpyrimidine-2,4-dion-1-yl]-1,6-heptadiene via building the pyrimidine ring utilizing 4-isocyanato-1,6-heptadiene intermediate.
- Bouhadir, Kamal H.,Zhou, Jing-Lan,Shevlin, Philip B.
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p. 1003 - 1010
(2007/10/03)
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- Acyclic analogues of adenosine bisphosphates as P2Y receptor antagonists: Phosphate substitution leads to multiple pathways of inhibition of platelet aggregation
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Activation by ADP of both P2Y1 and P2Y12 receptors in platelets contributes to platelet aggregation, and antagonists at these receptor subtypes have antithrombotic properties. In an earlier publication, we have characterized the SAR as P2Y1 receptor antagonists of acyclic analogues of adenine nucleotides, containing two phosphate groups on a symmetrically branched aliphatic chain, attached at the 9-position of adenine. In this study, we have focused on antiaggregatory effects of P2Y antagonists related to a 2-chloro-N6-methyladenine-9-(2-methylpropyl) scaffold, containing uncharged substitutions of the phosphate groups. For the known nucleotide (cyclic and acyclic) bisphosphate antagonists of P2Y1 receptors, there was a significant correlation between inhibition of aggregation induced by 3.3 μM ADP in rat platelets and inhibition of P2Y1 receptor-induced phospholipase C (PLC) activity previously determined in turkey erythrocytes. Substitution of the phosphate groups with nonhydrolyzable phosphonate groups preserved platelet antiaggregatory activity. Substitution of one of the phosphate groups with O-acyl greatly reduced the inhibitory potency, which tended to increase upon replacement of both phosphate moieties of the acyclic derivatives with uncharged (e.g., ester) groups. In the series of nonsymmetrically substituted monophosphates, the optimal antagonist potency occurred with the phenylcarbamate group. Among symmetrical diester derivatives, the optimal antagonist potency occurred with the di(phenylacetyl) group. A dipivaloyl derivative, a representative uncharged diester, inhibited ADP-induced aggregation in both rat (KI 3.6 μM) and human platelets. It antagonized the ADP-induced inhibition of the cyclic AMP pathway in rat platelets (IC50 7 μM) but did not affect hP2Y1 receptor-induced PLC activity measured in transfected astrocytoma cells. We propose that the uncharged derivatives are acting as antagonists of a parallel pro-aggregatory receptor present on platelets, that is, the P2Y12 receptor. Thus, different substitution of the same nucleoside scaffold can target either of two P2Y receptors in platelets.
- Xu, Bin,Stephens, Andrew,Kirschenheuter, Gary,Greslin, Arthur F.,Cheng, Xiaoquin,Sennelo, Joe,Cattaneo, Marco,Zighetti, Maddalena L.,Chen, Aishe,Kim, Soon-Ai,Kim, Hak Sung,Bischofberger, Norbert,Cook, Gary,Jacobson, Kenneth A.
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p. 5694 - 5709
(2007/10/03)
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- Intramolecular Reactions of N-Nitrenes with Alkenes
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Oxidation of 2-but-1-enyl- and 2-(1-phenylbut-1-enyl)-3-aminoquinazolin-4(3H)-ones (8) and (10), respectively, generates the corresponding N-nitrenes which are trapped intramolecularly by the double bonds.The results from competitive intramolecular trapping of the N-nitrene by different double bonds in 3-aminoquinazolones bearing bifurcated chains in position 2 indicate that these intramolecular nitrene additions are non-concerted and, as in the corresponding intramolecular addition to aromatic rings, proceed via 7-membered transition states with the nitrene functioning as an electrophile.
- Atkinson, Robert S.,Malpass, John R.,Skinner, Karen L.,Woodthorpe, Katherine L.
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p. 1905 - 1912
(2007/10/02)
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- Stereoelectronic control in acetal formation
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The cyclization under acidic conditions of bicyclic and monocyclic hydroxypropyl methoxytetrahydropyrans 1 and 4 is reported.At room temperature, compound 1 gives only cis tricyclic acetal 2.At reflux, compound 2 equilibrates to yield a mixture of cis and trans tricyclic acetals 2 (45percent) and 3 (55percent).Compound 4 gives directly the equilibrium mixture of cis and trans bicyclic acetals 5 (55percent) and 6 (45percent) at room temperature.The specific formation of 2 from 1 constitutes strong experimental evidence that acetal formation is controlled by stereoelectronic effects.The anomeric effect can be estimated (ca. 1.5 kcal/mol) from the equilibrium study of 2 and 3.This value confirms the result previously obtained by Descotes (9).
- Beaulieu, Normand,Dickinson, Robert A.,Deslongchamps, Pierre
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p. 2531 - 2536
(2007/10/02)
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