- Tuning the Connectivity, Rigidity, and Functionality of Two-Dimensional Zr-Based Metal-Organic Frameworks
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Presented herein is a group of highly stable Zr-based metal-organic frameworks with bowl-shaped dihydroanthracene-based tetratopic linkers as building blocks. Structural analysis reveals that these frameworks are all two-dimensional but comprise three distinct connectivities of Zr6 nodes. By using the steric hindrance of the nonplanar linker, the connectivity of Zr6 node can be tuned from 8-c to unusual 4-c. Further, through either one-pot synthesis or postsynthetic linker installation strategies, the connectivity of Zr6 node can be tuned from 8-c to 10-c by the insertion of a secondary linear dicarboxylate linker, from which not only the temperature-dependent flexibility of the structure can be effectively controlled with enhanced rigidity and thermal stability but also a scaffold for postsynthetic metalation of Pd(II) catalyst for Heck coupling reaction is offered.
- Jia, Shuping,Xiao, Xue,Li, Qiyang,Li, Yue,Duan, Zhigang,Li, Yiyang,Li, Xiaoteng,Lin, Zhihua,Zhao, Yonggang,Huang, Wei
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Read Online
- Design, synthesis, modelling studies and biological evaluation of 1,3,4-oxadiazole derivatives as potent anticancer agents targeting thymidine phosphorylase enzyme
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A series of novel 1,3,4-oxadiazole derivatives with substituted phenyl ring were designed and synthesized with an objective of discovering newer anti-cancer agents targeting thymidine phosphorylase enzyme (TP). The 1,3,4-oxadiazole derivatives were synthesized by simple and convenient methods in the lab. Chemical structure of the all the synthesized compounds were characterized by IR, 1H NMR and mass spectral methods and evaluated for cytotoxicity by MTT method against two breast cancer cell lines (MCF-7 and MDA-MB-231). Further, results of TP assay identified that 1,3,4-oxadiazole molecules displayed anti-cancer activity partially by inhibition of phosphorylation of thymidine. The TP assay identified SB8 and SB9 as potential inhibitors with anti-cancer activity against both the cell lines. The molecular docking studies recognized the orientation and binding interaction of molecule at the active site amino acid residues of TP (PDB: 1UOU). Acute toxicity studies of compound SB8 at the dose of 5000 mg/kg has identified no signs of clinical toxicity was observed. The SARs study of synthesized derivatives revealed that the substitution of phenyl ring with electron withdrawing group at ortho position showed significant TP inhibitory activity compared to para substitution. The experimental data suggests that 1,3,4-oxadiazole with substituted phenyl can be taken as a lead for the design of efficient TP inhibitors and active compounds which can be taken up for further studies.
- Bajaj, Shalini,Kumar, Maushmi S.,Tinwala, Hussain,YC, Mayur
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- Photo-induced energy transfer relay of N-heterocyclic carbene catalysis: an asymmetric α-fluorination/isomerization cascade
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The geometric configuration of olefin products is often driven by thermodynamic control in synthesis. Methods enabling switching of cis/trans selectivity are rare. Recently, photosensitized approaches have emerged as a powerful tool for accomplishing this task. In this report, we report an in situ isomerization of an N-heterocyclic carbene (NHC)-bound intermediate by a photo-induced energy transfer process that leads to selective access of chiral allylic fluorides with a cis-olefin geometry. In the absence of a photocatalyst or light, the reaction proceeds smoothly to give (E)-olefin products, while the (Z)-isomer can be obtained under photosensitizing conditions. Preliminary mechanistic experiments suggest that an energy transfer process might be operative. This journal is
- Jiang, Xinhang,Li, En,Chen, Jiean,Huang, Yong
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p. 729 - 732
(2021/02/05)
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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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- 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 Allylboranes via Cu(I)-Catalyzed B-H Insertion of Vinyldiazoacetates into Phosphine-Borane Adducts
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Cu(I) catalysts enable C-B bond formation via direct insertion of vinyldiazoacetates into B-H bonds of borane-phosphine Lewis adducts to form phosphine-protected allylboranes under mild conditions. The resulting allylborane-phosphine Lewis adducts can be used in the diastereoselective allylation of aldehydes directly without the need for removal of the phosphine. The allylation reaction proceeds with high diastereoselectivity and yields 5,6-disubstituted dihydropyranones after treatment with an appropriate acid.
- Drikermann, Denis,M??el, Robert S.,Al-Jammal, Walid K.,Vilotijevic, Ivan
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p. 1091 - 1095
(2020/02/15)
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- BICYCLIC KETONE COMPOUNDS AND METHODS OF USE THEREOF
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The invention provides novel compounds having the general formula (I): (I) wherein R1, the A ring and the B ring are as described herein, pharmaceutical compositions including the compounds, and methods of using the compounds.
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Page/Page column 79; 80
(2019/02/02)
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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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- 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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- Selective Palladium-Catalyzed Carbonylation of Alkynes: An Atom-Economic Synthesis of 1,4-Dicarboxylic Acid Diesters
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A class of novel diphosphine ligands bearing pyridine substituents was designed and synthesized for the first time. The resulting palladium complexes of L1 allow for chemo- and regioselective dialkoxycarbonylation of various aromatic and aliphatic alkynes affording a wide range of 1,4-dicarboxylic acid diesters in high yields and selectivities. Kinetic studies suggest the generation of 1,4-dicarboxylic acid diesters via cascade hydroesterification of the corresponding alkynes. Based on these investigations, the chemo- and regioselectivities of alkyne carbonylations can be controlled as shown by switching the ligand from L1 to L3 or L9 to give α,β-unsaturated esters.
- Liu, Jiawang,Dong, Kaiwu,Franke, Robert,Neumann, Helfried,Jackstell, Ralf,Beller, Matthias
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supporting information
p. 10282 - 10288
(2018/08/03)
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- Facile synthesis of 2-aryl or β,γ-unsaturated esters via 1,2-Migration from aryl or α,β-unsaturated ketones using thallium(III) p-tosylate
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The experiment reports that 2-aryl esters can be efficiently synthesized via 1,2-aryl migration from aryl ketones using thallium(III) p-tosylate in high yields. To determine optimum conditions for conversion of aryl ketones to 2-aryl esters, the effects of solvents were examined. An initial reaction of 4'-methoxypropiophenone and perchloric acid using thallium(III) p-tosylate in ethanol afforded ethyl 2-(4-methoxyphenyl)propanoate in only 10% yield after 24 h at room temperature. However, the corresponding reaction in ethanol/triethyl orthoformate (4/1) was completed in 1 h between 0 °C and room temperature to give ethyl 2-(4-methoxyphenyl)propanoate in 94% yield. The presence of triethyl orthoformate induced rapid ketalization of enol intermediate and facilitated 1,2-migration of the 4-methoxyphenyl group. The relative effectiveness of several metal salts was also examined for conversion of 2',4'-dimethoxypropiophenone to ethyl 2-(2,4-dimethoxyphenyl)propanoate. The solvents were evaporated off under reduced pressure, and the residue was dissolved in methylene chloride. The white precipitate was filtered off, and the resulting yellow solution was poured into saturated NaHCO3 solution and extracted with methylene chloride. The combined organic layers were dried over anhydrous MgSO4, filtered, and concentrated in vacuo. The residue was purified by vacuum distillation using a Kugelrohr apparatus to give 4g as a colorless liquid.
- Lee, Jae In
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p. 125 - 128
(2017/06/07)
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- A highly efficient Pd/CuI-catalyzed oxidative alkoxycarbonylation of α-olefins to unsaturated esters
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A new protocol for the alkoxycarbonylation of α-olefins to the corresponding unsaturated esters has been developed. Differently substituted styrenes were selectively converted to cinnamate derivatives, via C[sbnd]H bond functionalization. Various palladium sources, including heterogeneous ones, in combination with CuI exhibited a high catalytic efficiency using oxygen as the most cheap oxidant. Monocarbonylated products were obtained in good yields and high chemoselectivity working with a low CO pressure (2 atm) and an excess of air (35 atm) avoiding in this way explosion risks. Commercial cinnamate derivatives were prepared in good to excellent yields by this very simple one-pot procedure.
- Maffei, Mathias,Giacoia, Gabriele,Mancuso, Raffaella,Gabriele, Bartolo,Motti, Elena,Costa, Mirco,Della Ca’, Nicola
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p. 435 - 443
(2016/12/16)
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- Alkene Dioxygenation with Malonoyl Peroxides: Synthesis of γ-Lactones, Isobenzofuranones, and Tetrahydrofurans
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Treatment of homoallylic alcohols or carboxylic acids with malonoyl peroxide 1 provides a stereoselective method for the preparation of tetrahydrofurans, γ-lactones, and isobenzofuranones in 44-82% yield and up to 27:1 trans selectivity. Application of this simple and effective heterocyclization in the synthesis of the antidepressant citalopram is also described.
- Alamillo-Ferrer, Carla,Karabourniotis-Sotti, Marianna,Kennedy, Alan R.,Campbell, Matthew,Tomkinson, Nicholas C. O.
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supporting information
p. 3102 - 3105
(2016/07/13)
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- Use of formate salts as a hydride and a Co2 source in PGeP -palladium complex-catalyzed hydrocarboxylation of allenes
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Use of formate salts as a hydride as well as a CO2 source was achieved in a PGeP-palladium complex-catalyzed hydrocarboxylation of allenes through a highly efficient decarboxylation-carboxylation process. This reaction proceeds under mild conditions and provides an alternative strategy for utilizing formate salts as a C1 source.
- Zhu, Chuan,Takaya, Jun,Iwasawa, Nobuharu
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supporting information
p. 1814 - 1817
(2015/04/14)
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- LED lighting as a simple, inexpensive, and sustainable alternative for Wolff rearrangements
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The Wolff rearrangement is one of the best methods for chain homologation. However, it still suffers from many drawbacks with respect to its practical execution in the laboratory. We wish to demonstrate the use of commercial LED lamps as a sustainable alternative for the classic experimental protocols typically used for Wolff rearrangements. This journal is
- Bernardim, Barbara,Hardman-Baldwin, Andrea M.,Burtoloso, Antonio C. B.
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p. 13311 - 13314
(2015/02/19)
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- Ligand-Controlled Palladium-Catalyzed Alkoxycarbonylation of Allenes: Regioselective Synthesis of α,β- and β,γ-Unsaturated Esters
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The palladium-catalyzed regioselective alkoxycarbonylation of allenes with aliphatic alcohols allows to produce synthetically useful α,β- and β,γ-unsaturated esters in good yields. Efficient selectivity control is achieved in the presence of appropriate ligands. Using Xantphos as the ligand, β,γ-unsaturated esters are produced selectively in good yields. In contrast, the corresponding α,β-unsaturated esters are obtained with high regioselectivity in the presence of PPh2Py as the ligand. Preliminary mechanistic studies revealed that these two catalytic processes proceed by different reaction pathways. In addition, this novel protocol was successfully applied to convert an industrially available bulk chemical, 1,2-butadiene, into dimethyl adipate, which is a valuable feedstock for polymer and plasticizer syntheses, with high yield and TON (turnover number).
- Liu, Jie,Liu, Qiang,Franke, Robert,Jackstell, Ralf,Beller, Matthias
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supporting information
p. 8556 - 8563
(2015/07/15)
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- Palladium-catalyzed alkoxycarbonylation of terminal alkenes to produce α,β-unsaturated esters: The key role of acetonitrile as a ligand
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A mild protocol has been developed for the PdII-catalyzed alkoxycarbonylation of terminal olefins to produce α,β-unsaturated esters with a wide range of substrates. Key features are the use of MeCN as solvent (and/or ligand) to control the reactivity of the intermediate Pd complexes and the combination of CO with O2, which facilitates the CuII-mediated reoxidation of the Pd0 complex to Pd II and prevents double carbonylation. Acetonitrile is the key! A mild protocol has been developed for the PdII-catalyzed alkoxycarbonylation of terminal olefins to produce α,β-unsaturated esters with a wide range of substrates (see scheme). Key features are the use of MeCN as a solvent (and/or ligand) to control the reactivity of the intermediate Pd complexes and the combination of CO with O2, which facilitates the CuII-mediated reoxidation of Pd0 to PdII and prevents double carbonylation.
- Malkov, Andrei V.,Derrien, Nolwenn,Barlog, Maciej,Kocovsky, Pavel
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supporting information
p. 4542 - 4547
(2014/05/06)
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- Catalytic asymmetric α-aldol reaction of vinylogous N-heterocyclic carbene enolates: Formation of quaternary and labile tertiary stereocenters
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Simple N-heterocyclic carbene (NHC)-enolates are widely studied versatile species. However, their vinylogous siblings (i.e., vinylogous NHC-enolates) have been much less studied. Here we disclose the first catalytic asymmetric α-aldol reaction of vinylogous NHC-enolates. With trifluoropyruvate as the carbon electrophile, the efficient C-C bond formation process displays not only complete α-regioselectivity but also excellent stereocontrol over the two newly established challenging stereocenters (one quaternary and the other labile tertiary), furnishing a range of highly enantioenriched β,γ-unsaturated α-fluoroalkylated esters.
- Dong, Xiuqin,Sun, Jianwei
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supporting information
p. 2450 - 2453
(2014/05/20)
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- CuO/SiO2 as a simple, effective and recoverable catalyst for alkylation of indole derivatives with diazo compounds
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The purely inorganic copper oxide on silica catalyzes the reaction of methyl phenyldiazoacetate with N-methyl indole under mild reaction conditions, giving the alkylation (formally a C-H insertion) in position 3, and the catalyst can be recovered and reused at least in 5 consecutive runs with only minor loss in activity. The scope of the reaction includes various diazo compounds and indole or pyrrole derivatives leading to alkylation or cyclopropanation depending on the heterocycle structure. An alternative mechanism, without reduction of Cu(ii) to Cu(i), is proposed on the basis of the obtained results. The Royal Society of Chemistry 2013.
- Fraile, Jose M.,Le Jeune, Karel,Mayoral, Jose A.,Ravasio, Nicoletta,Zaccheria, Federica
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supporting information
p. 4327 - 4332
(2013/08/23)
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- Domino catalysis: Palladium-catalyzed carbonylation of allylic alcohols to β,γ-unsaturated esters
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Make it green: The Pd-catalyzed carbonylation of allylic alcohols with aliphatic alcohols represents a cost-effective, salt-free, and atom-economic carbonylation process generating water as the sole by-product. Mechanistic studies uncovered a new domino C-O coupling/carbonylation reaction pathway. Copyright
- Liu, Qiang,Wu, Lipeng,Jiao, Haijun,Fang, Xianjie,Jackstell, Ralf,Beller, Matthias
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supporting information
p. 8064 - 8068
(2013/08/23)
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- Application of sulfuryl chloride for the quick construction of β-chlorotetrahydrofuran derivatives from homoallylic alcohols under mild conditions
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An efficient and mild method is reported for the construction of β-chlorotetrahydrofuran derivatives by 5-endo chlorocycloetherification of homoallylic alcohols. The system employs sulfuryl chloride as the chlorinating agent under catalyst-free conditions. A variety of homoallylic alcohols with aryl or alkyl substituents were smoothly converted into β- chlorotetrahydrofurans in yields up to 98%.
- Zeng, Xianghua,Miao, Chengxia,Wang, Shoufeng,Xia, Chungu,Sun, Wei
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supporting information
p. 2391 - 2396
(2013/09/23)
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- Catalytic enantioselective synthesis of azacycloalkenes via intermolecular rhodium carbenoid C-H insertion/ring-closing metathesis sequence
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Enantiomerically enriched cyclopropanes and products of C-H insertion reactions were obtained in excellent combined yields and enantioselectivities as a consequence of rhodium-catalyzed decomposition of vinyl diazoacetate in the presence of tert-butoxycarbonyl-(Boc)-protected amines as trapping agents. A series of enantiomerically enriched six- to eight-membered nitrogen-containing heterocycles were subsequently prepared via ring-closing metathesis of the dienes catalyzed by ruthenium benzylidene complex.
- McMills, Mark C.,Humes, Ross J.,Pavlyuk, Oksana M.
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supporting information; experimental part
p. 849 - 851
(2012/03/11)
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- Palladium-catalyzed allylic cross-coupling reactions of primary and secondary homoallylic electrophiles
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The Pd(0)-catalyzed allylic cross-coupling of homoallylic tosylate substrates using boronic acids and pinacol esters is reported. The reaction uses 2-(4,5-dihydro-2-oxazolyl)quinoline (quinox) as a ligand and is performed at ambient temperature. The scope of the reaction is broad in terms of both the boronate transmetalating reagent and the substrate and includes secondary tosylates. Mechanistic studies support an alkene-mediated SN2-type stereoinvertive oxidative addition of unactivated primary and secondary alkyl tosylates.
- Stokes, Benjamin J.,Opra, Susanne M.,Sigman, Matthew S.
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supporting information; experimental part
p. 11408 - 11411
(2012/09/05)
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- Enantioselective synthesis of β,γ-unsaturated α-fluoroesters catalyzed by N-heterocyclic carbenes
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NHC meets F: NHC-bound enolates undergo a catalytic asymmetric fluorination reaction to β,γ-unsaturated α-fluoroesters, which are obtained with good efficiency and stereoselectivity (see scheme, NFSI=N- fluorobenzenesulfonimide). The strategy overcomes possible challenges, such as fluorination in the γ position and difluorination. Experimental evidence combined with DFT calculations provides insight into the reaction mechanism. Copyright
- Zhao, Yu-Ming,Cheung, Man Sing,Lin, Zhenyang,Sun, Jianwei
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p. 10359 - 10363
(2012/11/14)
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- Nucleophilic ring-opening of epoxide and aziridine acetates for the stereodivergent synthesis of β-Hydroxy and β-Amino γ-Lactams
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A highly regio- and stereoselective synthesis of novel β,γ- disubstituted γ-lactams with either an anti or syn relative configuration was developed from readily available epoxide and aziridine acetates. The key steps include the regio- and diastereocontrolled nucleophilic ring-opening of these three-membered heterocycles followed by mild reductive cyclization of the γ-azido ester intermediate. The method was also extended to an asymmetric synthesis of (4R,5S)-4-hydroxy-5-phenylpyrrolidin-2-one from a chiral epoxide acetate. The main features of this versatile synthesis of functionalized γ-lactams include the involvement of inexpensive reagents and mild conditions together with high chemical efficiency.
- Bisol, Tula B.,Bortoluzzi, Adailton J.,Sa, Marcus M.
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experimental part
p. 948 - 962
(2011/04/12)
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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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- Highly regioselective palladium-catalysed oxidative allylic C-H carbonylation of alkenes
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Pd-catalysed direct oxidative carbonylation of allylic C-H bonds with carbon monoxide was first described. This new procedure shows that the inherent requirement for a leaving group in the Tsuji-Trost palladium-catalysed allylic carbonylation can be lifted, which provides a new route for accessing more synthetically useful β-enoic acid esters with high regioselectivity. The Royal Society of Chemistry 2011.
- Chen, Huoji,Cai, Congbi,Liu, Xiaohang,Li, Xianwei,Jiang, Huanfeng
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p. 12224 - 12226
(2011/12/14)
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- An efficient phosphine-free heck reaction in water using Pd(l -Proline)2 as the catalyst under microwave irradiation
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The present report describes an efficient and simple protocol for phosphine-free Heck reactions in water using a Pd(l-proline)2 complex as the catalyst under controlled microwave irradiation conditions. This methodology is versatile and provides excellent yields of products in short reaction times and minimizes costs, operational hazards and environmental pollution. Georg Thieme Verlag Stuttgart.
- Allam, Bharat Kumar,Singh, Krishna Nand
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experimental part
p. 1125 - 1131
(2011/05/14)
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- Rhodium(II)-catalyzed cross-coupling of diazo compounds
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Nothing left to chance: A convenient protocol for selective cross-coupling of diazo compounds for the convergent synthesis of alkenes was developed (see scheme; EDG=aryl, heteroaryl, vinyl; R=O-alkyl, aryl). The selectivity control elements were identifie
- Hansen, Joorn H.,Parr, Brendan T.,Pelphrey, Philip,Jin, Quihui,Autschbach, Jochen,Davies, Huw M. L.
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supporting information; experimental part
p. 2544 - 2548
(2011/04/27)
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- Operationally simple and highly (E)-styrenyl-selective heck reactions of electronically nonbiased olefins
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Simple, mild, and efficient conditions are reported for a Pd 0-catalyzed Heck reaction that delivers high yields and selectivity for (E)-styrenyl products using electronically nonbiased olefin substrates bearing a range of useful functionality. Preliminary mechanistic studies demonstrate that the σ-donating DMA solvent is crucial for high selectivity. Further studies suggest that the catalyst distinguishes between β-hydrogens on the basis of their relative hydridic character, in contrast to previously reported PdII-catalyzed oxidative reaction conditions.
- Werner, Erik W.,Sigman, Matthew S.
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supporting information; experimental part
p. 9692 - 9695
(2011/08/06)
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- A highly selective and general palladium catalyst for the oxidative heck reaction of electronically nonbiased olefins
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A general, highly selective oxidative Heck reaction is reported. The reaction is high-yielding under mild conditions without the need for base or high temperatures, and the selectivity is excellent, without the requirement for electronically biased olefins or other specific directing groups. A preliminary mechanistic investigation suggests that the unusually high selectivity may be due to the catalyst's sensitivity to C-H bond strength in the selectivity-determining β-hydride elimination step.
- Werner, Erik W.,Sigman, Matthew S.
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supporting information; experimental part
p. 13981 - 13983
(2010/12/24)
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- FLUORINATION OF ORGANIC COMPOUNDS
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Methods for fluorinating organic compounds are described herein.
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Page/Page column 75; 76
(2010/07/10)
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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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scheme or table
p. 11273 - 11287
(2010/04/28)
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- Highly (E)-selective wadsworth-emmons reactions promoted by methylmagnesium bromide
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(Chemical Equation Presented) An experimentally simple protocol for the very highly (E)-selective Wadsworth-Emmons reaction [(E):(Z) selectivities in excess of 180:1 in some cases] of a range of straight-chain and branched aliphatic, substituted aromatic, and base-sensitive aldehydes via reaction with an alkyl diethylphosphonoacetate and MeMgBr is reported.
- Claridge, Timothy D. W.,Davies, Stephen G.,Lee, James A.,Nicholson, Rebecca L.,Roberts, Paul M.,Russell, Angela J.,Smith, Andrew D.,Toms, Steven M.
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supporting information; experimental part
p. 5437 - 5440
(2009/06/18)
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- A general and highly selective chelate-controlled intermolecular oxidative heck reaction
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A novel chelate-controlled intermolecular oxidative Heck reaction is reported that proceeds with a wide range of nonresonance stabilized α-olefin substrates and organoboron reagents to afford internal olefin products in good yields and outstanding regio- and E:Z stereoselectivities. Pd-H isomerization, common in many Heck reactions, is not observed under these mild, oxidative conditions. This is evidenced by outstanding E:Z selectivities (>20:1 in all cases examined), no erosion in optical purity for proximal stereogenic centers, and a tolerance for unprotected alcohols. Remarkably, a single metal/ligand combination, Pd/bis-sulfoxide complex 1, catalyzes this reaction over a broad range of coupling partners. Given the high selectivities and broad scope, we anticipate this intermolecular Heck reaction will find heightened use in complex molecule synthesis. Copyright
- Delcamp, Jared H.,Brucks, Alexandria P.,White, M. Christina
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supporting information; experimental part
p. 11270 - 11271
(2009/02/05)
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- Short and efficient synthesis of cryptophycin unit A
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(Chemical Equation Presented) Two short synthetic approaches toward cryptophycin unit A comprise a catalytic asymmetric dihydroxylation as the sole source of chirality, while all further stereogenic centers are introduced under substrate control. The key
- Eissler, Stefan,Nahrwold, Markus,Neumann, Beate,Stammler, Hans-Georg,Sewald, Norbert
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p. 817 - 819
(2007/10/03)
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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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- Cascade reactions: Sequential homobimetallic catalysis leading to benzofurans and β,γ-unsaturated esters
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The concatenation between a Pd(0)-promoted deallylation catalytic cycle and a Pd(II)-promoted heterocyclization catalytic cycle (an example of what we have named "sequential homobimetallic catalysis") has been shown to occur starting from 1-(2-allyloxyphenyl)-2-yn-1-ols 1 to afford 2-benzofuran-2- ylacetic esters 2 and β,γ-unsaturated esters in high yields under carbonylative conditions. In view of the conceptual as well as the synthetic importance of the process, the mechanistic aspects and the synthetic scope of the reaction have been investigated in detail. All the experimental evidence is in agreement with the sequential homobimetallic mechanism, and the reaction has proven to be of general synthetic applicability.
- Gabriele, Bartolo,Mancuso, Raffaella,Salerno, Giuseppe,Costa, Mirco
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p. 1101 - 1109
(2007/10/03)
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- Chemoselective Nucleophilic Attack on N-Acyl Derivatives of (S)-Ethyl 4,4-Dimethyl Pyroglutamate (DMPG)
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(Matrix presented) Heteronucleophiles and C-nucleophiles chemoselectively react with N-acyl (S)-ethyl 4,4-dimethyl pyroglutamate (DMPG) affording esters, amides, and ketones in high yield. The intramolecular process allows the stereoselective formation of β-hydroxy acids likely by formation and ring opening of the corresponding β-lactones.
- Mantecon, Susana,Vaquero, Juan J.,Alvarez-Builla, Julio,De La Puente, Maria Luz,Espinosa, Juan F.,Ezquerra, Jesus
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p. 3791 - 3794
(2007/10/03)
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- New results on the triplet photoreactivity of β,γ-unsaturated aldehydes: Diastereoselective synthesis of cyclopropanecarbaldehydes
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A comparative study on the triplet photoreactivity of a series of β,γ-unsaturated aldehydes and methyl ketones has been carried out. Aldehydes 14 and 20 were found to undergo the oxa-di-π-methane rearrangement yielding the corresponding cyclopropane carbaldehydes 15 and 21 diastereoselectively. Decarbonylations and 1,3-carbonyl migrations have been observed in some cases, although these reactions do not take place via a Norrish Type I mechanism.
- Armesto,Ortiz,Agarrabeitia,Aparicio-Lara
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p. 1149 - 1158
(2007/10/03)
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- Cyclopropanation of benzylidenemalononitrile with dialkoxycarbenes and free radical rearrangement of the cyclopropanes
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Thermolysis of 2-cinnamyloxy-2-methoxy-5,5-dimethyl-Δ3-1,3,4-oxadiazoline (1a) and the analogous 2-benzyloxy-2-methoxy compound (1b) at 110°C, in benzene containing benzylidenemalononitrile, afforded products of apparent regiospecific addition of methoxycarbonyl and cinnamyl (or benzyl) radicals to the double bond. When the thermolysis of 1a was run with added TEMPO, methoxycarbonyl and cinnamyl radicals were captured. Thermolysis of the 2,2-dibenzyloxy analogue (1c) in the presence of benzylidenemalononitrile gave an adduct that is formally the product of addition of benzyloxycarbonyl and benzyl radicals to the double bond. In this case, a radical addition mechanism could be ruled out, because the rate constant for decarboxylation of benzyloxycarbonyl radicals is very large. A mechanism that fits all of the results is predominant cyclopropanation of benzylidenemalononitrile by the dialkoxycarbenes derived from the oxadiazolines, in competition with fragmentation of the carbenes to radical pairs. The cyclopropanes so formed then undergo homolytic ring-opening to the appropriate diradicals. Subsequent β-scission of the diradicals to afford radical pairs, and coupling of those pairs, gives the final products. Thus, both carbene and radical chemistry are involved in the overall processes.
- Merkley,Venneri,Warkentin
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p. 312 - 318
(2007/10/03)
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- Piperidine derivatives having renin inhibiting activity
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Novel piperidine derivatives, their manufacture and use as medicaments, are disclosed. The invention is concerned with the novel piperidine derivatives of general formula I wherein R1, R2, R3, R4, Q, X, Z, m and n are as described herein.
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- Nickel-catalyzed electrochemical couplings of vinyl halides: Synthetic and stereochemical aspects
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Homo- and cross-coupling involving alkenyl halides have been performed efficiently using an electroassisted nickel-complex catalysis. Valuable product such as conjugated dienes, β,γ- or γ,δunsaturated esters, ketones, or nitriles, as well as alkenylated aryl compounds are thus prepared with high yields and high stereoselectivity. Partial isomerization is only observed in a few cases, when the alkenyl halide is involved in a late step of the catalytic cycle. This is the case in the preparation of (Z,Z)-1,3-diene.
- Cannes,Condon,Durandetti,Perichon,Nedelec
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p. 4575 - 4583
(2007/10/03)
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- Cp*Ru(II) and Cp*Ru(IV)-catalyzed reactions of CHX with vinyl C-H bonds: Competition between double bond homologation and olefin cyclopropanation by alkyl diazoacetate
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When diazoesters are used as carbene precursors, new Ru(II) and Ru(IV) complexes bearing various substitutents tethered ligands mediate the formal carbene insertion into C-H vinyl bonds of (substituted) styrenes to yield mostly E- and Z-styrylacetic esters (e.g. 4-phenylbut-3-enoates with styrene). This rarely observed reaction competes with the cyclopropanation of the double bond. The influence of steric and electronic factors on the two competitive reactions is reported. The observation that the most efficient C-H insertion catalysts also promote the ROMP of norbornene lend support to the formation of ruthenacyclobutanes as reaction intermediates.
- Simal, Francois,Demonceau, Albert,Noels, Alfred F.,Knowles,O'Leary, Shane,Maitlis, Peter M.,Gusev
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p. 163 - 170
(2007/10/03)
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- Nickel-catalyzed direct electrochemical cross-coupling between aryl halides and activated alkyl halides
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The electrochemical reduction of a mixture of aryl halides and activated alkyl halides in DMF in the presence of catalytic amount of NiBr2bipy leads to cross-coupling products in good to high yields. The method applies to the synthesis of α-aryl ketones, α-aryl esters, and allylated compounds from readily available organic halides. Optimization of the process has been obtained by slowly adding the most reactive organic halide (usually the activated alkyl halide) during the electrolysis which is best conducted at 70 °C when aryl bromides are involved.
- Durandetti, Muriel,Nedelec, Jean-Yves,Perichon, Jacques
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p. 1748 - 1755
(2007/10/03)
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- Palladium( 0) -catalyzed phenoxycarbonylation of allylic carbonates
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Phenoxycarbonylation of various allylic carbonates under various conditions in tetrahydrofuran is described. The nature and ratio of the products formed are dependent on the presence of water, carbon monoxide pressure and addition of various inorganic halides. The formation of a product arising from dimerization of the allylic carbonate is discussed.
- Goux, Catherine,Lhoste, Paul,Sinou, Denis,Masdeu, Anna
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p. 139 - 143
(2007/10/03)
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- Novel and efficient insertions of carbons carrying O-, S-, and N-Linked substituents: Synthesis of α-alkoxyalkyl, α-(Alkylthio)alkyl, and α-(Carbazol-9-yl)alkyl ketones
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A wide variety of benzotriazolyl-stabilized anions 2, obtained by the lithiation of 1-(α-alkoxyalkyl)-, 1-[α-(alkylthio)alkyl]-, and 1-[α-(carbazol-9-yl)alkyl]benzotriazoles 1, on reaction with aliphatic and aromatic aldehydes and ketones, followed by rearrangement induced by heating in the presence of zinc bromide, furnish one-carbon-homologated α-alkoxyalkyl, α-(alkylthio)alkyl, and α-(carbazol-9-yl)alkyl ketones 4 in simple one-pot operations in good yields with excellent regioselectivity. In several alkoxymethylene insertions, intermediate 2-alkoxyoxiranes were separated in good yields, demonstrating the epoxide mechanism for the rearrangements and providing a facile approach to poly substituted 2-alkoxyoxiranes, another class of important compounds.
- Katritzky, Alan R.,Xie, Linghong,Serdyuk, Larisa
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p. 7564 - 7570
(2007/10/03)
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- Vinylation of benzylic quaternary ammonium salts catalyzed by palladium
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The palladium-catalyzed vinylation of benzylic tributylammonium salts with a variety of olefins has been studied. A possible free radical mechanism is proposed.
- Yi,Zhuangyu,Hongwen
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p. 245 - 247
(2007/10/02)
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- Lithium 3-Lithio-3-tosylalkanoates: β-Acylvinyl Anion Equivalents of β-Lithiated α,β-Unsaturated Carboxylic Acids
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The dilithiation of β-tosylated propanoic, 2-methylpropanoic, and butanoic acid 10 with n-butyllithium at -78 deg C leads to the corresponding lithium 3-lithio-3-tosylalkanoates 11.They react with different electrophilic reagents (deuterium oxide, iodine, trimethylchlorosilane, alkyl halides, and acyl chlorides) to give the corresponding 3-substituted tosylated alkanoic acids 12.When carbonyl compounds are allowed to react with intermediates 11 followed by in situ lactonization with trifluoroacetic anhydride and base-promoted elimination α,β-butenolides are obtained.This methodology is applied to the direct synthesis of the rosefuran lactone precursor 14cg, the O-benzyl derivative of (+/-)-umbelactone (14ch), and (+/-)-andirolactone (14ci).The alkylation and acylation reactions of organolithium compounds 11 followed by esterification with hydrogen chloride in methanol and treatment with 1,8-diazabicycloundec-7-ene (DBU) afford α,β- and/or β,γ-unsaturated esters 17 and/or 18 and unsaturated 4-keto esters 19, respectively.The last methodology has been applied to the synthesis of the unsaturated 4-keto ester 19ae precursor of the seco acid of (+/-)-pyrenophorin (22).
- Bonete, Pedro,Najera, Carmen
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p. 3202 - 3209
(2007/10/02)
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- Ruthenium Complex-Catalyzed Carbonylation of Allylic Compounds
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Allylic alkyl carbonates are carbonylated under 40 atm of carbon monoxide at 100-120 deg C in the presence of a catalytic amount of Ru3(CO)12/1,10-phenanthroline to give α,β- or β,γ-unsaturated esters in good to high yields.For example, cinnamyl methyl carbonate afforded the corresponding β,γ-unsaturated esters, methyl trans-4-phenyl-3-butenoate (1) in 93percent yield.The regioselectivity in the carbonylation of crotyl methyl carbonate is unusual and it depends on the carbon monoxide pressure.The more sterically hindered carbon (γ-carbon) is predominantly carbonylated at 20-50 atm.When the reaction of cinnamyl methyl carbonate was performed at elevated temperature (150 deg C) without 1,10-phenanthroline, the dimer of 1, dimethyl 3-benzyl-2-(trans-2-phenylvinyl)glutarate, was obtained in 56percent yield.In the presence of secondary amines, allylic alkyl carbonates were carbonylated mainly at α-carbon to give α,β- or β,γ-unsaturated amides in high yields.
- Mitsudo, Take-aki,Suzuki, Nobuyoshi,Kondo, Teruyuki,Watanabe, Yoshihisa
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p. 7759 - 7765
(2007/10/02)
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