- Synthesis of (+) and (-)-Streptomyces coelicolor Butanolide 5 (SCB-5)
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Various 1-(1-hydroxyalkyl) paraconyl alcohols are important signaling molecules within antibiotics production in Streptomyces sp. Intending developing a flexible convergent chemical synthesis of such butanolides, a zwitterionic aza-Claisen rearrangement was chosen as reliable strategy generating the central stereotriad. Reaction of enantiopure N-allyl pyrrolidines and 4-phenylbutenoic acid fluoride delivered defined configured amides displaying the 2,3,1’ stereotriads. The configuration was determined by the allyl alcohol moiety indicating a complete remote stereo control. Amide removal by iodolactonization and proceeding reductions, halocyclization and elimination gave key alkylidene tetrahydrofuran derivatives. Stepwise degradation of the olefins through ozonolysis, reductive work-up and protecting group removal delivered both enantiomers of the target Streptomyces coelicolor butanolide 5.
- Brüggemann, Moritz,Donges, Jonas,Frank, Andrea,Hofmann, Sandra,Nubbemeyer, Udo,Schollmeyer, Dieter
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Read Online
- Copper-Catalyzed Phosphonation-Annulation Approaches to the Synthesis of β-Phosphonotetrahydrofurans Involving C-P and C-O Bonds Formation
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Substituted tetrahydrofuran derivatives play important roles as biological activities. A versatile method for the synthesis of β-phosphonotetrahydrofurans has been developed based on Cu-catalyzed difunctionalization of alkenes. This transformation would provide a new pathway for the formation of Csp3-P and Csp3-O bonds in one step. Furthermore, this copper catalyst system can be used in the synthesis of β-phosphonotetrahydropyrans and phosphono-β-butyrolactones. These reactions were also performed well by using 3 equiv of Mn(OAc)3·2H2O as the oxidant without copper catalyst.
- Gao, Yuzhen,Li, Xueqin,Chen, Weizhu,Tang, Guo,Zhao, Yufen
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Read Online
- Inter-and Intramolecular Cycloaddition Reactions of Ethenetricarboxylates with Styrenes and Halostyrenes
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Inter-and intramolecular cycloaddition reactions of ethenetricarboxylates with styrenes and α-halostyrenes have been investigated. The reactions of ethenetricarboxylates with styrenes or α-bromostyrenes in the presence of SnCl 4or SnBr 4stereoselectively gave 2,4-cis-substituted cyclobutanes. The intramolecular cycloaddition reactions of a series of styrene-functionalized ethenetricarboxylate amides, including in situ generated derivatives, showed high diversity of reaction modes depending on the structures and substituents of the substrates. The regioselectivity and stereoselectivity of the reactions as well as reaction mechanisms were discussed based on the DFT calculations.
- Yamazaki, Shoko,Wang, Zhichao,Iwata, Kentaro,Katayama, Khotaro,Sugiura, Hirotaka,Mikata, Yuji,Morimoto, Tsumoru,Ogawa, Akiya
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supporting information
p. 731 - 753
(2020/11/18)
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- Photo-Promoted Decarboxylative Alkylation of α, β-Unsaturated Carboxylic Acids with ICH2CN for the Synthesis of β, γ-Unsaturated Nitriles
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An efficient, catalyst/photocatalyst-free, and cost-effective methodology for the decarboxylative alkylation of α,β-unsaturated carboxylic acids to synthesize β,γ-unsaturated nitriles has been developed. The reaction proceeded in an environmentally benign atmosphere of blue light-emitting diode irradiation with K2CO3 and water at room temperature. The methodology worked for a wide range of substrates (22 examples) with up to 83% yield. The protocol is also compatible for gram-scale synthesis.
- Pan, Chunxiang,Yang, Chunhui,Li, Kangkui,Zhang, Keyang,Zhu, Yuanbin,Wu, Shiyuan,Zhou, Yongyun,Fan, Baomin
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p. 7188 - 7193
(2021/10/01)
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- Nickel-catalyzed electrocarboxylation of allylic halides with CO2
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Nickel-catalyzed regioselective electrocarboxylation of allylic halides with CO2at atmospheric pressure has been developed by adjusting reaction parameters, including catalyst, solvent, temperature and additive. β,γ-Unsaturated carboxylic acids were obtained in moderate to good yields and with high chain selectivity. This reaction shows tolerance to functional groups. In addition, cyclic voltammetry was performed to provide the possible mechanism of nickel-catalyzed CO2allylation.
- Wu, La-Xia,Deng, Fang-Jie,Wu, Lin,Wang, Huan,Chen, Tai-Jie,Guan, Ye-Bin,Lu, Jia-Xing
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p. 13137 - 13141
(2021/08/03)
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- Palladium-Catalyzed Direct C-H Arylation of 3-Butenoic Acid Derivatives
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We report herein a direct method to synthesize 4-aryl-3-butenoic acid through a carboxylic-acid-directed oxidative Heck reaction. The various 4-aryl-3-butenoic acids are easily prepared in moderate to good yields. In view of the promising bioactivity of 4-phenyl-3-butenoic acid previously reported, its derivatives reported here may be bioactive.
- Yang, Shan,Liu, Lingling,Zhou, Zheng,Huang, Zhibin,Zhao, Yingsheng
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supporting information
p. 296 - 299
(2021/01/13)
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- sEH Inhibitor or pharmaceutically acceptable composition thereof as well as preparation method and application thereof
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The invention provides sEH inhibitor or a pharmaceutically acceptable composition and a preparation method and application thereof, and belongs to the technical field of medicines. sEH Inhibitor or a pharmaceutically acceptable composition thereof according to the present invention is provided, and the sEH inhibitor has the structure shown I. sEH Inhibitor provided by the invention can stabilize an endogenous substance epoxy fatty acid with wide physiological activity, has a strong inhibition effect on human recombinant sEH, and can be used for regulating the generation of a plurality of pro-inflammatory cytokines. The invention relieves the stress of endoplasmic reticulum, prevents or reverses the dysfunction of endothelial dysfunction, stabilizes mitochondria function multiple action mechanisms to obviously relieve neuropathic pain, and can effectively avoid adverse reactions related to the target spot. Furthermore, the sEH inhibitor structure provided by the invention does not contain free carboxyl groups, can avoid adverse reactions such as gastrointestinal irritation caused by oral administration, and is small in adverse reaction, high in bioavailability, excellent in analgesic effect and small in administration amount.
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Paragraph 0125-0126
(2021/09/21)
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- An Enzymatic Platform for the Highly Enantioselective and Stereodivergent Construction of Cyclopropyl-δ-lactones
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Abiological enzymes offers new opportunities for sustainable chemistry. Herein, we report the development of biological catalysts derived from sperm whale myoglobin that exploit a carbene transfer mechanism for the asymmetric synthesis of cyclopropane-fused-δ-lactones, which are key structural motifs found in many biologically active natural products. While hemin, wild-type myoglobin, and other hemoproteins are unable to catalyze this reaction, the myoglobin scaffold could be remodeled by protein engineering to permit the intramolecular cyclopropanation of a broad spectrum of homoallylic diazoacetate substrates in high yields and with up to 99 % enantiomeric excess. Via an alternate evolutionary trajectory, a stereodivergent biocatalyst was also obtained for affording mirror-image forms of the desired bicyclic products. In combination with whole-cell transformations, the myoglobin-based biocatalyst was used for the asymmetric construction of a cyclopropyl-δ-lactone scaffold at a gram scale, which could be further elaborated to furnish a variety of enantiopure trisubstituted cyclopropanes.
- Chandgude, Ajay L.,Fasan, Rudi,Liu, Ningyu,Ren, Xinkun
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supporting information
p. 21634 - 21639
(2020/09/23)
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- Electroreductive Cobalt-Catalyzed Carboxylation: Cross-Electrophile Electrocoupling with Atmospheric CO2
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The chemical use of CO2 as an inexpensive, nontoxic C1 synthon is of utmost topical interest in the context of carbon capture and utilization (CCU). We present the merger of cobalt catalysis and electrochemical synthesis for mild catalytic carb
- Ackermann, Lutz,Ang, Nate W. J.,Oliveira, Jo?o C. A.
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supporting information
p. 12842 - 12847
(2020/06/02)
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- Intramolecular Cyclization of Vinyldiazoacetates as a Versatile Route to Substituted Pyrazoles
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Vinyldiazo compounds undergo a thermal electrocyclization to form pyrazoles in yields of up to 95percent. The reactions are operationally simple, use readily available starting materials, require no intervention of a catalyst, and enable the synthesis of mono-, di- A nd tri-substituted pyrazoles. With the ability to produce highly substituted pyrazoles and the flexibility in installing various types of substituents, this method constitutes a new entry to this valuable heterocyclic scaffold and may be of interest to all branches of the chemical industry.
- Drikermann, Denis,G?rls, Helmar,Kerndl, Valerie,Vilotijevic, Ivan
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supporting information
p. 1158 - 1162
(2020/07/20)
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- Synthesis of [18 F]-γ-Fluoro-α,β-unsaturated Esters and Ketones via Vinylogous 18 F-Fluorination of α-Diazoacetates with [18 F]AgF
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This communication reports a method for the vinylogous radiofluorination of α-diazoacetates to generate [18 F]-γ-fluoro-α,β-unsaturated esters and ketones in moderate to good radiochemical yields. The method uses no-carrier-added [18 F]AgF and is compatible with aromatic and non-aromatic substrates and a number of different functional groups. The labeling method is showcased in the synthesis of a fluorinated cholest-5-en-3-one derivative as well as a difluorinated product pertinent to drug discovery.
- Brooks, Allen F.,Ichiishi, Naoko,Jackson, Isaac M.,Lee, So Jeong,Sanford, Melanie S.,Scott, Peter J. H.,Thompson, Stephen
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supporting information
p. 4401 - 4407
(2019/11/21)
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- Direct Enantioselective and Regioselective Alkylation of β,γ-Unsaturated Carboxylic Acids with Chiral Lithium Amides as Traceless Auxiliaries
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Efficient asymmetric alkylation of β,γ-unsaturated carboxylic acids without prior functionalization is enabled by chiral lithium amides. Enantioselectivity is imparted by a putative mixed lithium amide-enediolate aggregate that acts a traceless auxiliary formed in situ, allowing for a direct asymmetric alkylation and a simple recovery of the chiral reagent.
- Yu, Kai,Miao, Bukeyan,Wang, Wenqi,Zakarian, Armen
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supporting information
(2019/03/19)
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- Stereoselective Ring-Opening of gem-Difluorocyclopropanes: An Entry to Stereo-defined (E,E)- and (E,Z)-Conjugated Fluorodienes
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The ring-opening of gem-difluorocyclopropyl acetaldehydes producing selectively (E,E)- and (E,Z)-conjugated fluorodienals is described. Two stereo-divergent methods are presented to access both stereoisomers from a common precursor, in high yield and selectivity. The mechanistic aspect of these transformations is discussed.
- Specklin, Simon,Fenneteau, Johan,Subramanian, Parthasarathi,Cossy, Janine
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supporting information
p. 332 - 336
(2018/01/17)
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- Indium-Catalyzed Direct Conversion of Lactones into Thiolactones and Selenolactones in the Presence of Elemental Sulfur and Selenium
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The direct conversion of lactones into thiolactones with elemental sulfur (S 8) catalyzed by InCl 3 /PhSiH 3 in a one-pot reaction is described. This catalytic system was successfully applied to the novel preparation of selenolactones from lactones and selenium.
- Sakai, Norio,Horikawa, Shuhei,Ogiwara, Yohei
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p. 565 - 574
(2017/12/26)
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- Cobalt-Catalyzed Allylic C(sp3)-H Carboxylation with CO2
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Catalytic carboxylation of the allylic C(sp3)-H bond of terminal alkenes with CO2 was developed with the aid of a Co/Xantphos complex. A wide range of allylarenes and 1,4-dienes were successfully transformed into the linear styrylacetic acid and hexa-3,5-dienoic acid derivatives in moderate to high yields, with excellent regioselectivity. The carboxylation showed remarkable functional group tolerability, so that selective addition to CO2 occurred in the presence of other carbonyl groups such as amide, ester, and ketone. Since styrylacetic acid derivatives can be readily converted into optically active γ-butyrolactones through Sharpless asymmetric dihydroxylation, this allylic C(sp3)-H carboxylation showcases a facile synthesis of γ-butyrolactones from simple allylarenes via short steps.
- Michigami, Kenichi,Mita, Tsuyoshi,Sato, Yoshihiro
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supporting information
p. 6094 - 6097
(2017/05/08)
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- Direct palladium-catalyzed carbonylative transformation of allylic alcohols and related derivatives
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A direct, palladium-catalyzed, carbonylative transformation of allylic alcohols for the synthesis of β,γ-unsaturated carboxylic acids has been developed. With formic acid as the CO source, various allylic alcohols were conveniently transformed into the corresponding β,γ-unsaturated carboxylic acids with excellent linear and (E)-selectivity. The reaction was performed under mild conditions; toxic CO gas manipulation and high-pressure equipment were avoided in this procedure.
- Wu, Fu-Peng,Peng, Jin-Bao,Fu, Lu-Yang,Qi, Xinxin,Wu, Xiao-Feng
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supporting information
p. 5474 - 5477
(2017/11/06)
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- (E)-beta,gamma-alkenyl carboxylic acid derivative and preparation method thereof
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The invention discloses an (E)-beta,gamma-alkenyl carboxylic acid derivative and a preparation method thereof. The preparation method disclosed by the invention comprises the following steps: in an organic solvent, under the condition that a nickel catalyst, a dinitrogen ligand, a reducer and an additive exist, carrying out a carboxylation reaction on an allyl alcohol substrate as shown in formula (II) and carbon dioxide. The preparation method disclosed by the invention is high in selectivity, the raw material reagents are easy to get and has high chemical selectivity and region selectivity, and the derivative is high in yield, high in purity, and low in generation cost and is more applicable for industrial production. (Refer to Specification).
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Paragraph 0150-0153
(2017/08/31)
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- Efficient Pd-Catalyzed Regio- and Stereoselective Carboxylation of Allylic Alcohols with Formic Acid
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Formic acid is efficiently used as a C1 source to directly carboxylate allylic alcohols in the presence of a low loading of palladium catalyst and acetic anhydride as additive to afford β,γ-unsaturated carboxylic acids with excellent chemo-, regio-, and stereoselectivity. The reaction proceeds through a carbonylation process with in situ-generated carbon monoxide under mild conditions, avoiding the use of high-pressure gaseous CO. A bisphosphine ligand with a large bite angle (4,5-bis{diphenylphosphino}-9,9-dimethylxanthene, Xantphos) was found to be uniquely effective for this transformation. The regio- and stereoconvergence of this reaction is ascribed to the thermodynamically favored isomerization of the allylic electrophile in the presence of the palladium catalyst.
- Fu, Ming-Chen,Shang, Rui,Cheng, Wan-Min,Fu, Yao
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p. 8818 - 8822
(2017/07/11)
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- Method for preparing beta, gama-unsaturated carboxylic acid compound
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The invention provides a method for preparing a beta, gamma-unsaturated carboxylic acid compound. The method comprises the steps of making an allylic alcohol compound of a formula 1 or a formula 2 react with formic acid in the presence of a palladium catalyst, a phosphorous ligand, acid anhydride and an organic solvent to obtain the beta, gamma-unsaturated carboxylic acid compound of a formula 3 or formula 4, wherein R1, R2 and R3 are defined in the description. Formic acid is utilized as a carboxylation reagent, and the beta, gamma-unsaturated carboxylic acid compound is low in price, safe, stable and low in toxicity; the yield is high, the operation is simple, and the economy is high; compared with an existing compounding method, the use of toxic gas carbon monoxide and/or an equivalent quantity of reactive metal reagents is avoided, and the method meets requirements for environment-friendly chemistry; in addition, the dose of catalysts is small, the reaction condition is mild, the reactant is high in conversion rate and product yield, and the method has a very good industrial prospect.
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Paragraph 0041; 0042; 0043; 0044; 0045; 0046; 0047; 0048
(2017/12/04)
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- Regioselective Ni-Catalyzed Carboxylation of Allylic and Propargylic Alcohols with Carbon Dioxide
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An efficient Ni-catalyzed reductive carboxylation of allylic alcohols with CO2 has been successfully developed, providing linear β,γ-unsaturated carboxylic acids as the sole regioisomer with generally high E/Z stereoselectivity. In addition, the carboxylic acids can be generated from propargylic alcohols via hydrogenation to give allylic alcohol intermediates, followed by carboxylation. A preliminary mechanistic investigation suggests that the hydrogenation step is made possible by a Ni hydride intermediate produced by a hydrogen atom transfer from water.
- Chen, Yue-Gang,Shuai, Bin,Ma, Cong,Zhang, Xiu-Jie,Fang, Ping,Mei, Tian-Sheng
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supporting information
p. 2969 - 2972
(2017/06/07)
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- Controlling the α/γ-Reactivity of Vinylogous Ketone Enolates in Organocatalytic Enantioselective Michael Reactions
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The first regio-, diastereo-, and enantioselective direct Michael reaction of β,γ-unsaturated ketones with nitroolefins is enabled by Br?nsted base/hydrogen-bonding bifunctional catalysis. A squaramide-substituted tertiary amine catalyzes the reaction of a broad range of β,γ-unsaturated ketones to proceed at the α-site exclusively, giving rise to adducts with two consecutive tertiary carbon stereocenters in diastereomeric ratios of up to >20:1 and enantioselectivities generally in the 90–98 % ee range.
- Iriarte, Igor,Olaizola, Olatz,Vera, Silvia,Gamboa, I?aki,Oiarbide, Mikel,Palomo, Claudio
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supporting information
p. 8860 - 8864
(2017/07/17)
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- A Chiral Electrophilic Selenium Catalyst for Highly Enantioselective Oxidative Cyclization
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Chiral electrophilic selenium catalysts have been applied to catalytic asymmetric transformations of alkenes over the past two decades. However, highly enantioselective reactions with a broad substrate scope have not yet been developed. We report the first successful example of this reaction employing a catalyst based on a rigid indanol scaffold, which can be easily synthesized from a commercially available indanone. The reaction efficiently converts β,γ-unsaturated carboxylic acids into various enantioenriched γ-butenolides under mild conditions.
- Kawamata, Yu,Hashimoto, Takuya,Maruoka, Keiji
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supporting information
p. 5206 - 5209
(2016/05/19)
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- Enantioselective Trifluoromethylthiolating Lactonization Catalyzed by an Indane-Based Chiral Sulfide
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Enantioselective trifluoromethylthiolation, especially of alkenes, is a challenging task. In this work, we have developed an efficient approach for enantioselective trifluoromethylthiolating lactonization by designing an indane-based bifunctional chiral sulfide catalyst and a shelf-stable electrophilic SCF3 reagent. The desired products were formed with diastereoselectivities of >99:1 and good to excellent enantioselectivities. The transformation represents the first enantioselective trifluoromethylthiolation of alkenes and the first enantioselective trifluoromethylthiolation that is enabled by a catalyst with a Lewis basic sulfur center.
- Liu, Xiang,An, Rui,Zhang, Xuelin,Luo, Jie,Zhao, Xiaodan
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supporting information
p. 5846 - 5850
(2016/05/09)
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- Characterization of an epoxide hydrolase from the Florida red tide dinoflagellate, Karenia brevis
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Epoxide hydrolases (EH, EC 3.3.2.3) have been proposed to be key enzymes in the biosynthesis of polyether (PE) ladder compounds such as the brevetoxins which are produced by the dinoflagellate Karenia brevis. These enzymes have the potential to catalyze kinetically disfavored endo-tet cyclization reactions. Data mining of K. brevis transcriptome libraries revealed two classes of epoxide hydrolases: microsomal and leukotriene A4 (LTA4) hydrolases. A microsomal EH was cloned and expressed for characterization. The enzyme is a monomeric protein with molecular weight 44 kDa. Kinetic parameters were evaluated using a variety of epoxide substrates to assess substrate selectivity and enantioselectivity, as well as its potential to catalyze the critical endo-tet cyclization of epoxy alcohols. Monitoring of EH activity in high and low toxin producing cultures of K. brevis over a three week period showed consistently higher activity in the high toxin producing culture implicating the involvement of one or more EH in brevetoxin biosynthesis.
- Sun, Pengfei,Leeson, Cristian,Zhi, Xiaoduo,Leng, Fenfei,Pierce, Richard H.,Henry, Michael S.,Rein, Kathleen S.
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- SULFAMATE DERIVATIVE COMPOUND FOR USE IN PREVENTING OR TREATING EPILEPSY
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The present invention relates to a pharmaceutical composition for treating or preventing epilepsy containing a sulfamate derivative compound and/or pharmaceutically acceptable salt thereof as an active ingredient. Furthermore, the present invention relates to a method for treatment or prevention epilepsy comprising administering a sulfamate derivative compound in a pharmaceutically effective amount to a subject in need of treatment or prevention of epilepsy.
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Page/Page column 144
(2015/06/25)
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- Catalytic asymmetric aminolactonization of 1,2-disubstituted alkenoic acid esters: Efficient construction of aminolactones with an all-carbon quaternary stereo-centre
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Chiral BOX-Cu(OTf)2 catalyzed enantioselective aminolactonization of the tert-butyl ester of alkenoic acids has been developed via in situ aziridination using PhINNs as the nitrene source. It provides exclusively trans-γ- and δ-amino lactones including an additional all-carbon quaternary stereo-centre with up to 98% ee in good to excellent yields. the Partner Organisations 2014.
- Hajra, Saumen,Akhtar, Sk Md Samim,Aziz, Sk Mohammad
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supporting information
p. 6913 - 6916
(2014/06/23)
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- Dual targeting of adenosine A2A receptors and monoamine oxidase B by 4H-3,1-benzothiazin-4-ones
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Blockade of A2A adenosine receptors (A2AARs) and inhibition of monoamine oxidase B (MAO-B) in the brain are considered attractive strategies for the treatment of neurodegenerative diseases such as Parkinson's disease (PD). In the present study, benzothiazinones, e.g., 2-(3-chlorophenoxy)- N-(4-oxo-4H-3,1-benzothiazin-2-yl)acetamide (13), were identified as a novel class of potent MAO-B inhibitors (IC50 human MAO-B: 1.63 nM). Benzothiazinones with large substituents in the 2-position, e.g., methoxycinnamoylamino, phenylbutyrylamino, or chlorobenzylpiperazinylbenzamido residues (14, 17, 27, and 28), showed high affinity and selectivity for A 2AARs (Ki human A2AAR: 39.5-69.5 nM). By optimizing benzothiazinones for both targets, the first potent, dual-acting A2AAR/MAO-B inhibitors with a nonxanthine structure were developed. The best derivative was N-(4-oxo-4H-3,1-benzothiazin-2-yl)-4-phenylbutanamide (17, Ki human A2A, 39.5 nM; IC50 human MAO-B, 34.9 nM; selective versus other AR subtypes and MAO-A), which inhibited A 2AAR-induced cAMP accumulation and showed competitive, reversible MAO-B inhibition. The new compounds may be useful tools for validating the A2AAR/MAO-B dual target approach in PD.
- St??el, Anne,Schlenk, Miriam,Hinz, Sonja,Küppers, Petra,Heer, Jag,Gütschow, Michael,Müller, Christa E.
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p. 4580 - 4596
(2013/07/19)
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- Regioselective copper-catalyzed carboxylation of allylboronates with carbon dioxide
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In the presence of a Cu(I)/NHC catalyst, the reactions of allylboronic pinacol esters with CO2 (1 atm) are highly regioselective, giving exclusively the more substituted β,γ-unsaturated carboxylic acids in most cases. A diverse array of substituted carboxylic acids can be prepared via this method, including compounds featuring all-carbon quaternary centers.
- Duong, Hung A.,Huleatt, Paul B.,Tan, Qian-Wen,Shuying, Eileen Lau
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p. 4034 - 4037
(2013/09/02)
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- PHENYLALKYL SULFAMATE COMPOUND AND MUSCLE RELAXANT COMPOSITION COMPRISING THE SAME
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The present invention relates to novel phenylalkyl sulfamate compounds, a method for preventing or treating a disease associated with muscle spasm. The present invention ensures the enhancement of muscle relaxation activity essential for alleviation of muscle spasm, such that it is promising for preventing or treating various diseases associated with muscle spasm.
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Page/Page column 149
(2014/01/08)
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- Regioselective ring opening and isomerization reactions of 3,4-epoxyesters catalyzed by boron trifluoride
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Efficient ring opening of 3,4-epoxyesters with alcohols to produce 4-alkoxy-3-hydroxyesters and their isomerization into 4-ketoesters using boron trifluoride as the catalyst are presented. Both transformations are simple and efficient methods for the synthesis of the above named synthetically useful compounds.
- Izquierdo, Javier,Rodriguez, Santiago,Gonzalez, Florenci V.
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supporting information; experimental part
p. 3856 - 3859
(2011/09/19)
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- Method for regio- and stereoselective synthesis of (E)-Β,γ- unsaturated acids from aldehydes under solvent-free conditions
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Synthesis of (E)-β,-γunsaturated acids from aldehydes with malonic acid has been explored under solvent-free conditions. The modified Knoevenagel condensation reaction with N-methyl morpholine (NMM) as catalyst exhibits highly β,-γ regioselectivity and exclusively E-stereoselectivity. A mechanism accounting for both regio- and stereoselectivity has been proposed and preliminarily studied. Copyright Taylor & Francis Group, LLC.
- Zhang, Shi-Jie,Hu, Wei-Xiao
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experimental part
p. 3093 - 3100
(2010/12/19)
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- 2-(Trimethylsilyl)-1,3-dithiane 1-oxide as a convenient reagent for the transformation of aldehydes and ketones into homologous carboxylic acids
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Aldehydes and ketones were converted into the corresponding homologous carboxylic acids in two steps by treatment with 2-(trimethylsilyl)-1,3-dithiane 1-oxide. A modified Peterson olefination of the carbonyl compounds gave ketene thioacetal sulfoxides that were readily cleaved in acidic acetonitrile to give the required carboxylic acids. Georg Thieme Verlag Stuttgart New York.
- Krohn, Karsten,Cludius-Brandt, Stephan
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experimental part
p. 2616 - 2620
(2010/09/10)
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- Efficient synthesis of cryptophycin-52 and novel para- Alkoxymethyl unit A analogues
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Cryptophycins are a family of highly cytotoxic, cyclic depsipeptides. They display antitumour activity that is largely maintained for multidrug-resistant tumour cells. Cryptophycins are composed of four building blocks (units A-D) that correspond to the respective amino and hydroxy acids. A new synthetic route to unit A allows the selective generation of all four stereogenic centres in a short, efficient and reliable synthesis and con-tributes to an easier and faster synthesis of cryptophycins. The first two stereogenic centres are introduced by a catalytic asymmetric dihydroxylation, whereas the remaining two stereogenic centres are introduced with substrate control of diastereoselectivity. The stereogenic diol function also serves as the epoxide precursor. The approach was used to synthesise the native unit A building block as well as three paraalkoxymethyl analogues from which cryptophycin-52 and three analogous cryptophycins were prepared. Macrocyclisation of the seco-depsipeptides was based on ring-closing metathesis.
- Eissler, Stefan,Bogner, Tobias,Nahrwold, Markus,Sewald, Norbert
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experimental part
p. 11273 - 11287
(2010/04/28)
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- Catalytic use of selenium electrophiles in cyclizations
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A new and convenient one-pot method for a catalytic addition-elimination reaction using selenium electrophiles has been developed. In the presence of 5 mol % diphenyl diselenide, [bis(trifluoroacetoxy)iodo]benzene in acetonitrile converted a range of (E)-3-butenoic acids into the corresponding butenolides in good yields.
- Browne, Danielle M.,Niyomura, Osamu,Wirth, Thomas
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p. 3169 - 3172
(2008/02/10)
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- On the mechanism of the selenolactonization reaction with selenenyl halides
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The mechanism of selenocyclization reactions of β,γ-unsaturated acids and their derivatives has been studied. The reactions of (E)-4-phenyl-3-butenoic acid 10 and its silyl and alkyl esters with benzeneselenenyl chloride (PhSeCl) and bromide (PhSeBr) have been examined by VT-NMR and in situ IR spectroscopic methods. Whereas the reactions of the acid 10 in the presence of a base were irreproducible and complicated, reactions of the silyl esters were clean and spontaneously and quantitatively afforded a chloroselenylation adduct at -70 °C as a single (Markovnikov) isomer. This adduct underwent three processes as the temperature was raised: (1) reversal to the starting materials, (2) isomerization to the anti-Markovnikov product, and (3) cyclization to the selenolactone 12. All of these processes are believed to proceed via a seleniranium ion the intermediacy of which was established by independent synthesis and spectroscopic identification. The reversible formation of chloro selenide adducts was unambiguously established by crossover experiments. The reaction of 10 with PhSeBr was found to be rapid but thermodynamically unfavorable at room temperature.
- Denmark, Scott E.,Edwards, Michael G.
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p. 7293 - 7306
(2007/10/03)
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- Stereoselective access to functionalized β-γ unsaturated acids
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Stereoselective synthesis of vinylstannanes bearing a carboxylic acid function was achieved from β-γ alkynoic acids via hydrostannation, stannylcupration or silastannation reactions. Regioselectivity is highly dependent on the nature of the stannylanions used and on protection of the carboxylic acid function.
- Thibonnet, Jér?me,Abarbri, Mohamed,Parrain, Jean-Luc,Duchêne, Alain
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p. 4433 - 4441
(2007/10/03)
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- A new synthesis of β,γ-alkenyl carboxylic acids from α,β-alkenyl carboxylic acid chlorides and α,β-alkenyl aldehydes with one-carbon elongation
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Reaction of the lithium α-sulfinyl carbanion of chloromethyl phenyl sulfoxide with α,β-alkenyl carboxylic acid chlorides gave γ,δ-alkenyl α-chloro-β-keto sulfoxides in variable yields. The keto sulfoxides were also synthesized from α,β-alkenyl aldehydes in two steps in good overall yields: addition of the lithium α-sulfinyl carbanion of chloromethyl phenyl sulfoxide to α,β-alkenyl aldehydes followed by oxidation of the adducts with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone or Dess-Martin periodinane. These products were treated in sequence with potassium hydride, tert-butyllithium, and 5% aqueous sodium hydroxide, in one flask to give β,γ-alkenyl carboxylic acids with one-carbon elongation in good yields. The procedure offers a new method for synthesizing β,γ-alkenyl carboxylic acids from α,β-alkenyl carboxylic acid chlorides and α,β-alkenyl aldehydes with one-carbon elongation.
- Satoh, Tsuyoshi,Nakamura, Akira,Iriuchijima, Atsuko,Hayashi, Yasumasa,Kubota, Ko-Ichi
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p. 9689 - 9696
(2007/10/03)
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- Correlation of rates of uncatalyzed and hydroxide-ion catalyzed ketene hydration. A mechanistic application and solvent isotope effects on the uncatalyzed reaction
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Rates of hydration of a number of ketenes were measured in neutral and basic solution using flash photolytic techniques, and rate constants for their uncatalyzed, k(uc), and hydroxide-ion catalyzed, k(HO), reactions were determined. These results, plus additional data from the literature, were found to provide the remarkably good correlation log k(uc) = -3.21 + 1.14 log k(HO), which spans 10 orders of magnitude in reactivity and includes 31 ketenes. This good correlation implies that uncatalyzed and hydroxide-ion catalyzed ketene hydraton occur by similar reaction mechanisms, which for the hydroxide-ion catalyzed process is known to involve nucleophilic attack on the carbonyl carbon atom of the ketene. Rate constants for phenylhydroxyketene, on the other hand, do not fit this correlation, which suggests that the mechanistic assignment upon which these rate constants are based may not be correct. Solvent isotope effects on these uncatalyzed ketene hydrations are weak; most are less than k(H)/k(D) = 2. It is argued that these isotope effects are largely, if not entirely, secondary in nature and that they are consistent with both a reaction mechanism in which nucleophilic attack of a single water molecule on the ketene carbonyl carbon atom produces a zwitterionic intermediate and also a mechanism that avoids this intermediate by passing through a cyclic transition state involving several water molecules.
- Andraos, John,Kresge, A. Jerry
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p. 508 - 515
(2007/10/03)
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- SiO2 catalysed expedient synthesis of [E]-3-alkenoic acids in dry media
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Aliphatic aldehydes with α-hydrogens and malonic acid undergo decarboxylative condensation on the surface of SiO2 when subjected to microwave irradiation generating βγ-unsaturated acids in high yields.
- Kumar, H.M. Sampath,Reddy, B.V. Subba,Reddy, E. Jagan,Yadav
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p. 2401 - 2404
(2007/10/03)
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- A Stereospecific Access to Allylic Systems Using Rhodium(II)-Vinyl Carbenoid Insertion into Si-H, O-H, and N-H Bonds
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Rhodium-catalyzed decomposition of α-vinyldiazoesters in the presence of silanes, alcohols, ethers, amines, and thiols have been shown to produce the corresponding α-silyl, α-hydroxy, α-alkoxy, α-amino, and α-thioalkoxy esters in generally good yield with a complete retention of the stereochemistry of the double bond of the diazo precursor. An extension of the process in homochiral series has also been devised using either a chiral auxiliary attached to the ester function or achiral α-vinyldiazoesters and Doyle's chiral catalyst Rh2(MEPY)4. In the former approach, pantolactone as chiral auxiliary gave diastereoselectivities of up to 70%, while the second approach produced the desired allylsilane with ee as high as 72%. On the other hand, Rh2(MEPY)4-catalyzed insertion into the O-H bond of water led to poor or no enantioselectivity in good agreement with recent literature reports.
- Bulugahapitiya, Priyadarshanie,Landais, Yannick,Parra-Rapado, Liliana,Planchenault, Denis,Weber, Valery
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p. 1630 - 1641
(2007/10/03)
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- Activation of C-O and C-N Bonds in Allylic Alcohols and Amines by Palladium Complexes Promoted by CO2. Synthetic Applications to Allylation of Nucleophiles, Carbonylation, and Allylamine Disproportionation
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The direct activation of the C-O bonds in allylic alcohols catalyzed by palladium complexes has been accelerated by carrying out the reactions under CO2. On reaction with diethylamine, allyl alcohol can be converted into N,N-diethylallylamine in the presence of palladium complexes at room temperature under normal pressure of carbon dioxide. Allylation of various carbon nucleophiles such as β-keto esters and β-diketones can be achieved by using allylic alcohols directly in the presence of palladium complexes and CO2. Direct carbonylation of allylic alcohols into unsaturated carboxylic acids can be catalyzed by palladium complexes under the pressure of CO and CO2. Disproportionation of diallylamine into triallylamine and allylamine is also catalyzed by palladium complexes in the presence of CO2. On the basis of studies on the behavior of η3-allylpalladium hydrogencarbonate complexes with the nucleophiles, mechanisms are proposed to account for the palladium-catalyzed allylation processes influenced by CO2.
- Sakamoto, Masato,Shimizu, Isao,Yamamoto, Akio
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p. 1065 - 1078
(2007/10/03)
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- Tributylstannyl 4-tributylstannylbut-3-enoate: A useful C-4 homologating agent. Application to the synthesis of aryl iodolactones
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Tributylstannyl 4-tributylstannylbut-3-enoate, readily prepared by radical hydrostannation, is used for the transfer of a but-3-enoic acid synthon. Some of the potentialities of this synthon are established by the synthesis of aryl iodolactones or tetralones (one of them is a key intemediate for ABT-200 synthesis).
- Thibonnet, Jerome,Abarbri, Mohamed,Parrain, Jean-Luc,Duchene, Alain
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p. 7507 - 7510
(2007/10/03)
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- Palladium-Catalyzed Double and Single Carbonylation of Aryl Halides and Allylic Compounds
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After a brief introduction summarizing the author's previous work concerning the double carbonylation of aryl halides catalyzed by palladium complexes, newly found catalytic processes (1) for converting allylic formates and chlorides into β,γ-unsaturated acids and (2) the double carbonylation of allylic chlorides to β,γ-unsaturated α-keto amides are described.Mechanisms which reasonably account for the catalytic processes are proposed on the basis of studies concerning the properties of the organopalladium complexes.
- Yamamoto, Akio
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p. 433 - 446
(2007/10/02)
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- Aza- and oxacarbonylations of allyl phosphates catalyzed by rhodium carbonyl cluster. Selective synthesis of β,γ-unsaturated amides, esters, and acids
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Rhodium-catalyzed carbonylation of allyl phosphates under CO (20 atm) at 50 deg C proceeds very efficiently in the presence of amines, alcohols, and water to give the corresponding β,γ-unsaturated amides, esters, and acids, respectively.These carbonylations occur with high regioselectivity at the less substituted carbon of allyl unit to give linear β,υ-unsaturated acid derivatives.
- Imada, Yasushi,Shibata, Ou,Murahashi, Shun-Ichi
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p. 183 - 194
(2007/10/02)
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- Oxidative Cleavage of Indane-1,2,3-trione-Ene Adducts; a Convenient Synthesis of Allyl and Allenyl Carboxylic Acids
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The ene adducts formed by the thermal reaction of indane-1,2,3-trione with olefins or terminal alkynes are cleaved in good yield by reaction with periodic acid in dry diethyl ether.Thereby the 2-hydroxyindane-1,2-dione moiety in the adduct is replaced by a CO2H group; hence indane-1,2,3-trione is a masked equivalent of carbon dioxide in the ene reaction.The allyl or allenyl carboxylic acid may be separated from the co-products (phthalic acid and anhydride) by extraction into hexane.
- Gill, G. Bryon,Idris, Muhammad S. Hj.,Kirollos, Kirollos S.
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p. 2367 - 2370
(2007/10/02)
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- Reaction of 2-Butenoic Acid Dianion and Its N-(4-Methoxyphenyl)amide with Methoxy-Substituted Arynes
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N-(4-Methoxyphenyl)-1-butenamide dianion (6), generated by the reaction of N-(4-methoxyphenyl)-2-butenamide (3) with LDA or LTMP, undergoes exclusive 4-arylation with various methoxy-substituted arynes 2a-e yielding mixtures consisting of a N-(4-methoxyphenyl)-(E)-4-aryl-3-butenamide (9) (85-90percent) and a N-(4-methoxyphenyl)-(E)-4-aryl-2-butenamide 9' (10-15percent).Under certain conditions, 4,4-diarylated products 12 are also obtained. 2-Butenoic acid dianion (14) also reacts with methoxy-substituted arynes affording predominantly 4-aryl-3-butenoic acids 15 and minor amountsof 4-aryl-2-butenoic acids 15'.The exclusive low temperature (-30 to -40 deg C) 4-addition of arynes to dianion 14 is in contrast to the predominant 2-addition that 14 undergoes with certain aldehydes and ketones at comparable temperatures.The mixtures of 4-arylbutenoic acids 15 and 15' and 4-arylbutenamides 9 and 9' were readily hydrogenated (Pd/C) and esterified (MeOH/H2SO4) to synthetically valuable methyl 4-arylbutanoates 17.
- Deshmukh, Abdul Rakeeb,Tran, Long,Biehl, Edward R.
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p. 667 - 670
(2007/10/02)
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- Palladium-Catalyzed, Atmospheric Pressure Carbonylation of Allylic Halides under the Influence of Sodium Hydroxide or Alkoxides. A Facile Synthesis of β,γ-Unsaturated Acids
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The palladium-catalyzed, atmospheric-pressure carboxylation of allylic halides occurs readily in an aqueous sodium hydroxide/organic solvents two-phase system, giving β,γ-unsaturated acids.Phosphine complexes (I, L=m-(Ph2P)C6H4SO3Na; II, L=Ph3P) or Na2 (III) can be used as the catalyst.Atmospheric-pressure alkoxycarbonylation is realized under the influence of a homogeneous alcoholic solution of sodium alkoxide.Phosphine-free palladium complexes, such as 2 or III, are the favored catalyst. β,γ-Unsaturated esters are obtained in high yields.
- Okano, Tamon,Okabe, Nobuyuki,Kiji, Jitsuo
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p. 2589 - 2593
(2007/10/02)
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- Pd(O)-CATALYZED ELECTROREDUCTIVE CARBOXYLATION OF ARYL HALIDES, β-BROMOSTYRENE, AND ALLYL ACETATES WITH CO2
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Electroreductive carboxylation of aryl halides, β-bromostyrene, and allyl acetates has been performed in an aprotic solvent saturated with carbon dioxide in the presence of a catalytic amount of PdCl2(Ph3P)2 and/or Pd(Ph3P)4.
- Torii, Sigeru,Tanaka, Hideo,Hamatani, Takeshi,Morisaki, Kazuo,Jutand, Anny,et al.
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p. 169 - 172
(2007/10/02)
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- Enecarboxylation with Diethyl Oxomalonate as an Enophilic Equivalent of Carbon Dioxide. A Synthesis of Allylcarboxylic Acids
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Allylcarboxylic acids are prepared from alkenes by a two-stage process which is synthetically equivalent to an ene reaction of carbon dioxide: (1) ene reaction with diethyl oxomalonate to afford an α-hydroxylmalonic ester and (2) oxidative bisdecarboxylation of the derived α-hydroxymalonic acid.The oxidative bisdecarboxylation of α-hydroxymalonic acids can sometimes be achieved with sodium periodate.However, occasionally decarboxylation is only partial, leading to pyruvic rather than carboxylic acids.While the bisdecarboxylations with periodate have previously been "buffered with a little pyridine", the latter is now shown to inhibit the reaction.In fact the pyruvate:carboxylate ratio can be a sensitive function of the amount of pyridine present in the reaction mixture, and the oxidative decarboxylation can be controlled to yield almost exclusively carboxylic or pyruvic acid.An effective new reagent, ceric ammonium nitrate in aqueous acetonitrile, was discovered for oxidative bisdecarboxylation of α-hydroxymalonic acids.Fortunately this reagent provides good to excellent yields of allylcarboxylic acids in many cases for which sodium periodate proved unsatisfactory.
- Salomon, Mary F.,Pardo, Simon N.,Salomon, Robert G.
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p. 3797 - 3802
(2007/10/02)
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