- Ligand-controlled divergent dehydrogenative reactions of carboxylic acids via C–H activation
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Dehydrogenative transformations of alkyl chains to alkenes through methylene carbon-hydrogen (C–H) activation remain a substantial challenge. We report two classes of pyridine-pyridone ligands that enable divergent dehydrogenation reactions through palladium-catalyzed b-methylene C–H activation of carboxylic acids, leading to the direct syntheses of a,b-unsaturated carboxylic acids or g-alkylidene butenolides. The directed nature of this pair of reactions allows chemoselective dehydrogenation of carboxylic acids in the presence of other enolizable functionalities such as ketones, providing chemoselectivity that is not possible by means of existing carbonyl desaturation protocols. Product inhibition is overcome through ligand-promoted preferential activation of C(sp3)–H bonds rather than C(sp2)–H bonds or a sequence of dehydrogenation and vinyl C–H alkynylation. The dehydrogenation reaction is compatible with molecular oxygen as the terminal oxidant.
- Wang, Zhen,Hu, Liang,Chekshin, Nikita,Zhuang, Zhe,Qian, Shaoqun,Qiao, Jennifer X.,Yu, Jin-Quan
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p. 1281 - 1285
(2021/12/10)
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- Macrolactam Synthesis via Ring-Closing Alkene-Alkene Cross-Coupling Reactions
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Reported herein is a practical method for macrolactam synthesis via a Rh(III)-catalyzed ring closing alkene-alkene cross-coupling reaction. The reaction proceeded via a Rh-catalyzed alkenyl sp2 C-H activation process, which allows access to macrocyclic molecules of different ring sizes. Macrolactams containing a conjugated diene framework could be easily prepared in high chemoselectivities and Z,E stereoselectivities.
- Goh, Jeffrey,Loh, Teck-Peng,Maraswami, Manikantha
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supporting information
p. 9724 - 9728
(2020/12/21)
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- Palladium-Catalyzed Visible-Light-Driven Carboxylation of Aryl and Alkenyl Triflates by Using Photoredox Catalysts
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A visible-light-driven carboxylation of aryl and alkenyl triflates with CO2 is developed by using a combination of Pd and photoredox catalysts. This reaction proceeds under mild conditions and can be applied to a wide range of substrates including acyclic alkenyl triflates.
- Shimomaki, Katsuya,Nakajima, Tomoya,Caner, Joaquim,Toriumi, Naoyuki,Iwasawa, Nobuharu
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supporting information
p. 4486 - 4489
(2019/06/24)
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- Macrolide Synthesis through Intramolecular Oxidative Cross-Coupling of Alkenes
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A RhIII-catalyzed intramolecular oxidative cross-coupling between double bonds for the synthesis of macrolides is described. Under the optimized reaction conditions, macrocycles containing a diene moiety can be formed in reasonable yields and with excellent chemo- and stereoselectivity. This method provides an efficient approach to synthesize macrocyclic compounds containing a 1,3-conjugated diene structure.
- Jiang, Bing,Zhao, Meng,Li, Shu-Sen,Xu, Yun-He,Loh, Teck-Peng
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supporting information
p. 555 - 559
(2018/02/21)
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- Preparation of cyclopentyl (f) ene-1-boronic acid frequency that ester method
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The invention discloses a method of preparing cyclopenten/cyclohexen-1-yl-boronic acid pinacol ester from methyl 1-cyclopentene/cyclohexene-1-carboxylate by three-step continuous operations. The method includes subjecting the raw material to alkaline hydrolysis to form the corresponding 1-alkylene carboxylic acid; performing addition with bromine; performing elimination and decarboxylation at the same time under the existence of DBU or DMAP to produce 1-bromo cyclopentene/cyclohexene; and allowing the 1-bromo cyclopentene/cyclohexene and methoxyboronic acid pinacol ester to form an ester under the existence of magnesium metal by a one-pot process to obtain the cyclopenten/cyclohexen-1-yl-boronic acid pinacol ester. The method is high in continuity, simple and convenient in operations, free of low-temperature reactions, and capable of obtaining the 1-bromo cyclopentene/cyclohexene intermediate with high purity and meeting market demands. The method adopts one-pot-process of Grignard reaction/esterification, so that the method is more convenient in operations and has less by-products, and the product is easier in rectification purification.
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Paragraph 0017; 0018
(2016/10/31)
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- Improved synthesis and in vitro study of antimicrobial activity of α,β-unsaturated and α-bromo carboxylic acids
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A series of α,β-unsaturated and α-bromo carboxylic acids were identified as potent antimicrobial agents. The antimicrobial activity was evaluated using the broth microdilution method. All acids 1-12 exhibited a significant activity against nine laboratory control strains of bacteria and two strains of yeast Candida albicans. The tested acids were efficiently prepared by optimized phase-transfer-catalyzed (PTC) reactions of ketones with bromoform and aqueous lithium hydroxide in alcoholic solvent with triethylbenzyl ammonium chloride (TEBA) as catalyst.
- Vitnik, Vesna D.,Milenkovi, Marina T.,Dilber, Sanda P.,Vitnik, Zeljko J.,Juranic, Ivan O.
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experimental part
p. 741 - 750
(2012/10/07)
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- One-step conversion of ketones to conjugated acids using bromoform
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Phase-transfer-catalyzed (PTC) reactions of ketones with bromoform and aqueous lithium hydroxide in alcoholic solvent result in the formation of ,-unsaturated carboxylic acids. The reaction was performed at room temperature for 24h. The corresponding conj
- Vitnik,Ivanovic,Vitnik,Orevic,Zizak,Juranic,Juranic
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experimental part
p. 1457 - 1471
(2009/09/26)
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- Synthesis of α,β-unsaturated carboxylic acids by nickel(II)-catalyzed electrochemical carboxylation of vinyl bromides
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Electrochemical carboxylation of alkyl-substituted vinyl bromides (1a-1g) in the presence of 20 mol% of NiBr2?bpy under an atmospheric pressure of carbon dioxide with a platinum cathode and a magnesium anode gave the corresponding α,β-unsaturated carboxylic acids (2a-2g) in yields of 53-82%.
- Kamekawa, Hisato,Kudoh, Hiroki,Senboku, Hisanori,Tokuda, Masao
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p. 917 - 918
(2007/10/03)
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- Structure-activity relationships of unsaturated analogues of valproic acid
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The principal metabolite of valproic acid (VPA), 2-ene VPA, appears to share most of VPA's pharmacological and therapeutic properties while lacking its hepatotoxicity and teratogenicity, thus making it a useful lead compound for the development of safer antiepileptic drugs. Analogues of 2-ene VPA were evaluated for anticonvulsant activity in mice using the subcutaneous pentylenetetrazole test. Cyclooctylideneacetic acid exhibited a potency markedly exceeding that of VPA itself with only modest levels of sedation. Potency, as either ED50 or brain concentration, was highly correlated (r > 0.85) with volume and lipophilicity rather than with one of the shape parameters calculated by molecular modeling techniques, arguing against the existence of a specific receptor site. Instead, a role for the plasma membrane in mediating the anticonvulsant effect is suggested.
- Palaty,Abbott
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p. 3398 - 3406
(2007/10/02)
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- Dienediolates of Unsaturated Carboxylic Acids in Synthesis. Synthesis of Cyclohexenones and Polycyclic Ketones by Tandem Michael-Dieckmann Decarboxylative Annulation of Unsaturated Carboxylic Acids.
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Substituted 2-cyclohexenones 4 to 7 and hexahydronaphthalenones and hexahydroindenones 13 to 18 are prepared by tandem Michael-Dieckmann addition of lithium dienediolates of acyclic and alicyclic unsaturated carboxylic acids to the lithium salts of the same or other unsaturated carboxylic acids.
- Aurell, Maria J.,Gavina, Pablo,Mestres, Ramon
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p. 2571 - 2582
(2007/10/02)
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- PHOTOCYCLIZATION OF ENAMIDES. 38 REDUCTIVE PHOTOCYCLIZATION OF α-(METHYLTHIO)- AND α-(ARYLTHIO)ENAMIDES
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Reductive photocyclization of α-(methylthio)enamide (2) gave exclusively six-membered lactams (3) and (4) while the same reaction of α-(arylthio)enamides (6) and (12) was found to afford five-membered lactams (7) and (13) as major products.A novel total s
- Naito, Takeaki,Tanada, Hiromi,Suzuki, Yumiko,Saito, Haruko,Kiguchi, Toshiko,Ninomiya, Ichiya
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p. 2345 - 2366
(2007/10/02)
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- Antiparasitic agents
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The invention provides novel compounds having the formula: STR1 wherein R when taken individually is H; R1 when taken individually is H or OH; R and R1 when taken together represent a double bond; R2 is an alpha-branched C3 -C8 alkyl, alkenyl, alkynyl, alkoxyalkyl or alkylthioalkyl group; a C3 -C8 cycloalkyl, C5 -C8 cycloalkenyl or C5 -C8 cycloalkylalkyl group, any of which may be substituted by methylene or one or more C1 -C4 alkyl groups or halo atoms; or a 3 to 6 membered oxygen or sulphur containing heterocyclic ring which may be substituted by one or more C1 -C4 alkyl groups or halo atoms; R3 is hydrogen or methyl; R4 is H or 4'-(alpha-L-oleandrosyl)-alpha-L-oleandrosyloxy with the proviso that when R2 is alkyl it is not isopropyl or sec-butyl; when R4 is H, each of R and R1 is H, and R2 is not methyl or ethyl; and when R4 is H, R is H, R1 is OH, and R2 is not 2-buten-2-yl, 2-penten-2-yl or 4-methyl-2-penten-2-yl. The compounds are broad spectrum antiparasitic agents having utility as anthelmintics, ectoparasiticides, insecticides and acaricides. The invention also provides a process for producing the novel avermectin and milbemycin derivatives by adding a carboxylic acid or derivative thereof to a fermentation of an avermectin or milbemycin producing organism.
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- (Lig)Ni(0) induced preparation of mono- and dicarboxylic acids from cyclopentene and carbon dioxide
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Cyclopentene is shown to be an ideal substrate for coupling reactions with (Lig)nickel(0) systems. By variation of the ligands and addition of promoters, it is possible by successive application of carbon dioxide or carbon monoxide to prepare highly selectively series of cyclopentane- and cyclopentenecarboxylic acids (six examples), 4, 5, 6, 11, 14, 15, cyclopentanedicarboxylic acids (three examples), 7, 8, 12, or 2-hydroxycyclopentanecarboxylic acid (9) in good yields. The C5-skeleton is retained in the products.
- Hoberg,Ballesteros,Sigan,Jegat,Milchereit
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p. 395 - 398
(2007/10/02)
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- Optically pure (S)-cyclopent-2-en-1-ol and (S)-3-methoxycylopentene
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Optically pure (S)-cyclopent-2-en-1-ol, D20 -137.9 deg (c 1.1, CHCl3), and (S)-3-methoxycyclopentene, D20 -116.9 deg (c 3.86, n-hexane), were prepared from ethyl (1R,2S)-2-hydroxycylopentanecarboxylate, which is readily available by yeast reduction of ethyl 2-oxocyclopentanecarboxylate.The optical purity of the alcohol was determined from its Mosher ester, and that of the ether by gas chromatography using a Ni-4-Pin column.
- Wahhab, Amal,Tavares, Donald F.,Rauk, Arvi
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p. 1559 - 1563
(2007/10/02)
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- STEREOSPECIFIC NICKEL AND PHASE TRANSFER CATALYZED CARBONYLATION OF VINYL BROMIDES AND CHLORIDES
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Nickel cyanide catalyzes the carbonylation of vinyl bromides and chlorides to α,β-unsaturated acids.
- Alper, Howard,Amer, Ibrahim,Vasapollo, Giuseppe
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p. 2615 - 2616
(2007/10/02)
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- An Asymmetric Synthesis of 2-Substituted Piperidines through Ozonolysis of Cyclopentenes and Reductive Aminocyclization
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By the action of ozone, sodium cyanoborohydride and the optically active benzylic amines 2, the 1-substituted cyclopentenes 1, 5 and 9 were converted to a diastereometric mixture of 1,2-disubstituted piperidines (3, 6 and 10), respectively.Hydrogenation of these compounds and the following work-up yielded optically active 2-alkylpiperidines (4, up to 68percente.e.), pipecolic acid (7, 84percent e.e.) and 2-(hydroxymethyl)piperidine (11, up to 85percente.e.).Chromatographic separation of the major isomers of 3b and 6 enabled optically pure coniine (4b) and pipecolic acid (7) to be prepared, respectively.
- Kawaguchi, Mamoru,Hayashi, Osamu,Sakai, Noriyuki,Hamada, Masayuki,Yamamoto, Yukio,Oda, Jun'ichi
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p. 3107 - 3112
(2007/10/02)
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- Angiotensin Converting Enzyme Inhibitors as Antihypertensive Agents: 1--L-prolines
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The synthesis of 1--L-prolines, 1--L-prolines and related benzoyl derivatives as pure isomers is described.The abilities of all the compounds to inhibit angiotensin converting enzyme (ACE) in vitro and in vivo and to lower the systolic blood pressure in renal hypertensive dogs were determined.Three of them, namely 1-carbonyl>-L-proline (10f(R,S)), 1--L-proline (10g(R,S)), and 1-carbonyl>-L-proline (16f(R,S)), werefound to be as potent as captopril in reducing blood pressure.The influence of chirality and ring size on the ACE inhibition is described.
- Ciabatti, Romeo,Padova, Giovanna,Bellasio, Elvio,Tarzia, Giorgio,Depaoli, Adele,et al.
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p. 411 - 417
(2007/10/02)
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- 1-[(-2-MERCAPTOCYCLOALKYL)CARBONYL]-L-PROLINE DERIVATIVES, THE PROCESS FOR THEIR MANUFACTURE, THE INTERMEDIATES FOR THEIR SYNTHESIS AND THEIR USE AS ANTI-HYPERTENSIVE AGENTS
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1-[(2-Mercaptocycloalkyl)carbonyl]-L-proline derivatives of the formula STR1 wherein R, R 1, and R 2, each independently, represent hydrogen or a (C 1-C 4)alkyl radical, n represents the integer 1, 2, 3, 4, or 5, and, in each of the n (CR' 2) groups, R' r
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- SYNTHESIS AND PROPERTIES OF 2-DIAZO-1,3-DICARBONYL COMPOUNDS. V. SYNTHESIS AND 1,2-NUCLEOPHILIC REARRANGEMENTS OF SOME 2-DIAZO-3-HYDROXY-1-CYCLOHEXANONES
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2-Diazo-3-hydroxy, 2-diazo-3-hydroxy-5,5-dimethyl, and 2-diazo-3-hydroxy-4,4,6,6-tetramethyl-1-cyclohexanones were obtained by reduction of 2-diazo 1,3-diketones of the cyclohexane series, and their spectral characteristics were determined.Photolytic, catalytic, and thermal elimination of nitrogen in these diazo compounds is only accompanied by 1,2-nucleophilic rearrangements.During photolysis of the diazohydroxycyclohexanones in an aqueous medium the main reaction path is a Wolff rearrangement, i.e., ring contraction with the formation of hydroxy and unsaturated acids of the cyclopentane series and some of their derivatives.Acid decomposition of the diazohydroxycyclohexanones leads mainly to an alkyl shift as a result of which (hydroxymethylene)cyclopentanones are formed with ring contraction.
- Nikolaev, V. A.,Zhdanova, O. V.,Korobitsyna, I. K.
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p. 488 - 498
(2007/10/02)
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- α Chain dienic prostanoic acid derivatives
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α Diene 16-hydroxy prostanoic acid derivatives displaying valuable pharmacological properties, e.g., gastric antisecretory, are described herein.
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