- 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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Read Online
- A fluorous phase approach to rhodium-catalyzed carbenoid reactions with diazoacetates
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The cyclopropanation of alkenes with methyl diazoacetate in dichloromethane was catalyzed by rhodium(II) carboxylates containing a perfluoralkyl chain (Rh2L4, L = OOCC7F15 and OOC-C6H4-4-C
- Endres, Andreas,Maas, Gerhard
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Read Online
- Electrochemical Ring-Opening Dicarboxylation of Strained Carbon-Carbon Single Bonds with CO2: Facile Synthesis of Diacids and Derivatization into Polyesters
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Diacids are important monomers in the polymer industry to construct valuable materials. Dicarboxylation of unsaturated bonds, such as alkenes and alkynes, with CO2 has been demonstrated as a promising synthetic method. However, dicarboxylation of C-C single bonds with CO2 has rarely been investigated. Herein we report a novel electrochemical ring-opening dicarboxylation of C-C single bonds in strained rings with CO2. Structurally diverse glutaric acid and adipic acid derivatives were synthesized from substituted cyclopropanes and cyclobutanes in moderate to high yields. In contrast to oxidative ring openings, this is also the first realization of an electroreductive ring-opening reaction of strained rings, including commercialized ones. Control experiments suggested that radical anions and carbanions might be the key intermediates in this reaction. Moreover, this process features high step and atom economy, mild reaction conditions (1 atm, room temperature), good chemoselectivity and functional group tolerance, low electrolyte concentration, and easy derivatization of the products. Furthermore, we conducted polymerization of the corresponding diesters with diols to obtain a potential UV-shielding material with a self-healing function and a fluorine-containing polyester, whose performance tests showed promising applications.
- Liao, Li-Li,Wang, Zhe-Hao,Cao, Ke-Gong,Sun, Guo-Quan,Zhang, Wei,Ran, Chuan-Kun,Li, Yiwen,Chen, Li,Cao, Guang-Mei,Yu, Da-Gang
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supporting information
p. 2062 - 2068
(2022/02/10)
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- Boronic Acid-Mediated Photocatalysis Enables the Intramolecular Hydroacylation of Olefins Using Carboxylic Acids
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An intramolecular hydroacylation of olefins using carboxylic acids (CAs) has been developed. With the aid of a boronic acid, CAs can be used as acyl-radical precursors in catalytic photoredox reactions driven by visible light. The CAs are easily converted into their corresponding cyclic ketones without the need to use any stoichiometric activating reagents. Mechanistic studies implied that the formation of an “ate” complex from the CA and boronic acid is crucial for the generation of the acyl radical equivalent from the unreactive carboxy group.
- Nanjo, Takeshi,Takemoto, Yoshiji,Yumura, Taichi
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supporting information
(2022/03/31)
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- Green Esterification of Carboxylic Acids Promoted by tert-Butyl Nitrite
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In this work, the green esterification of carboxylic acids promoted by tert-butyl nitrite has been well developed. This transformation is compatible with a broad range of substrates and exhibits excellent functional group tolerance. Various drugs and substituted amino acids are applicable to this reaction under near neutral conditions, with good to excellent yields.
- Cheng, Xionglve,Jiang, Gangzhong,Li, Xingxing,Tao, Suyan,Wan, Xiaobing,Zhao, Yanwei,Zheng, Yonggao
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supporting information
p. 2713 - 2718
(2021/06/25)
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- HETEROBICYCLIC CARBOXAMIDES AND USES THEREOF
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Provided herein are heterobicyclic cyclopropanecarboxamide and heterobicyclic carboxamide compounds. In particular, provided herein are compounds that affect the function of kinases in a cell, and that are useful as therapeutic agents or with therapeutic agents. The compounds provided herein are useful in the treatment of a variety of diseases and conditions including eye diseases such as glaucoma, cardiovascular diseases, inflammatory diseases, and diseases characterized by abnormal growth, such as cancers. Also provided herein are compositions comprising heterobicyclic cyclopropanecarboxamide or heterobicyclic carboxamide compounds.
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Page/Page column 39
(2021/03/19)
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- An efficient one-pot oxidative esterification of aldehydes to carboxylic esters using B(C6F5)3-TBHP
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A simple and efficient protocol for oxidative esterification of diverse aldehydes with alcohols was accomplished with tert-butyl hydroperoxide and 1 mol % of tris(pentafluorophenyl)borane [B(C6F5)3] to generate the corresponding esters in good to excellent yields. The present protocol represents compatibility with wide range of functional groups as well as exceptional tolerance toward acid labile protecting groups such as TBDPS, TBDMS, acetonide, and Boc.
- Guggilapu, Sravanthi Devi,Prajapti, Santosh Kumar,Babu, Bathini Nagendra
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supporting information
p. 889 - 892
(2015/02/05)
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- Synthesis of a novel C2-symmetric bis-oxazoline (=bis[4,5-dihydrooxazole]) and its application as chiral ligand in asymmetric transition metal catalysis
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The new C2-symmetric bis-oxazoline (=bis[4,5-dihydrooxazole]) 2 with a chiral trans-(2R,3R)-2,3-bis(3,5-diphenylphenyl)cyclopropylidene (=trans-(2R,3R)-2,3-bis([1,1′: 3′,1″-terphenyl]-5′-yl) cyclopropylidene) backbone was efficiently synthesized (Scheme). All synthetic steps were easy to perform and led to the desired product in good overall yields. Compound 2 was tested and compared as ligand in several enantioselective catalytic reactions such as palladium(0)-catalyzed enantioselective allylic alkylations and copper(I)-catalyzed enantioselective cyclopropanations and aziridinations. Copyright
- Goek, Yasar,Van Der Eycken, Johan
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experimental part
p. 831 - 838
(2012/06/16)
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- Novel trans-2-aryl-cyclopropylamine analogues as potent and selective dipeptidyl peptidase IV inhibitors
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A series of trans-2-aryl-cyclopropylamine derived compounds were synthesized and evaluated their biological activities against DPP-IV. The structure-activity relationships (SAR) led to the discovery of novel series of DPP-IV inhibitors, having IC50 values of 100 nM with excellent selectivity over the closely related enzymes, DPP8, DPP-II and FAP. The studies identified a potent and selective DPP-IV inhibitor 24b, which exhibited the ability to both significantly inhibit plasma DPP-IV activity in rats and improve glucose tolerance in lean mice and diet induced obese mice.
- Tsai, Ting-Yueh,Hsu, Tsu,Chen, Chiung-Tong,Cheng, Jai-Hong,Yeh, Teng-Kuang,Chen, Xin,Huang, Chung-Yu,Chang, Chung-Nien,Yeh, Kai-Chia,Hsieh, Su-Huei,Chien, Chia-Hui,Chang, Yi-Wei,Huang, Chih-Hsiang,Huang, Yu-Wen,Huang, Chen-Lung,Wu, Ssu-Hui,Wang, Min-Hsien,Lu, Cheng-Tai,Chao, Yu-Sheng,Jiaang, Weir-Torn
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scheme or table
p. 2388 - 2399
(2009/09/05)
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- Stereo- and regiocontrol in ene-dimerisation and trimerisation of 1-trimethylsilyl-3-phenylcyclopropene
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1-Trimethylsilyl-3-phenylcyclopropene and its 2D-analog undergo a highly stereocontrolled ene-reaction to give a single dimer. Further reaction leads to one or more trimers derived through two ene-reactions. The dimer formed easily undergoes cycloaddition
- Sheshenev, Andrey E.,Baird, Mark S.,Bolesov, Ivan G.,Shashkov, Alexandre S.
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experimental part
p. 10552 - 10564
(2010/03/01)
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- Efficient syntheses of four stable-isotope labeled (1R)-menthyl (1S,2S)-(+)-2-phenylcyclopropanecarboxylates
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Many carbenoid cyclopropanation reactions promoted by chiral catalysts give product mixtures reflecting impressive diastereo- and enantioselectivities. Few provide a single chiral product efficiently. This limitation has been overcome in cyclopropanations of styrene and isotopically labeled styrenes with α-diazoacetates. Convenient syntheses on a 20 g scale of each of four chiral isotopically labeled (1R)-menthyl (1S,2S)-2- phenylcyclopropanecarboxylates (the 1-d-3-13C, 1,(3S)-d2, 1,2,(3S)-d3, and 1,3,3-d3 isotopomers) of better than 99% ee have been realized. The Royal Society of Chemistry 2006.
- Keliher, Edmund J.,Burrell, Richard C.,Chobanian, Harry R.,Conkrite, Karina L.,Shukla, Rajesh,Baldwin, John E.
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p. 2777 - 2784
(2008/09/16)
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- Synthesis of polymer bound azabis(oxazoline) ligands and their application in asymmetric cyclopropanations
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Aza(bisoxazoline) ligands were attached to various polymeric supports and the resulting immobilized ligands were evaluated in copper(I)-catalyzed asymmetric cyclopropanations. The efficiency of these transformations depends greatly on the polymeric support, on the protocol being applied for the immobilization of the ligands, and on the preparation of the catalysts.
- Werner, Heiko,Herrerias, Clara I.,Glos, Michael,Gissibl, Anja,Fraile, Jose M.,Perez, Ignacio,Mayoral, Jose A.,Reiser, Oliver
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p. 125 - 132
(2007/10/03)
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- Concave 1,10-phenanthrolines as tailored ligands for copper(I)-catalyzed diastereoselective cyclopropanations
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Alkenyloxy-substituted aryl bridgeheads have been connected to 2,9-dichloro-1,10-phenanthroline (11) either by Suzuki coupling or by nucleophilic aromatic substitution. The resulting di- or tetraalkenes 12 or 17 have been cyclized by ring-closing metathesis to give concave 1,10-phenanthrolines 14 and 19, differing from other concave 1,10-phenanthrolines 1 in their geometries. The influence of the shapes of these ligands and those of the related concave 1,10-phenanthrolines 1a-f and 2 on the stereochemistry of the copper(I)-catalyzed cyclopropanation of indene (3) and styrene (4) has been investigated, identifying factors that favour the formation of thermodynamically less stable syn-cyclopropanes 6 and 7. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Luening, Ulrich,Fahrenkrug, Frank
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p. 916 - 923
(2007/10/03)
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- Diruthenium(I,I) saccharinate complexes: Synthesis, molecular structure, and evaluation as catalysts for carbenoid reactions of diazoacetates
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The dinuclear ruthenium complexes [Ru2(μ-sac)2(CO)6] (1), [Ru2(μ-sac)2(CH3CN)2(CO)4] (3), [Ru2(μ-sac)2(CO)5(PPh3)] (4) and [Ru2(μ-sac)2(CO)4(PPh3)2] (5) as well as the tetranuclear ruthenium complex [Ru2(μ-sac)2(CO)5]2 (2) (sac = saccharinate, C7H4NO3S-) were synthesized starting from Ru3(CO)12 and saccharin. X-ray crystal structure analysis of 1, 3A × p-xylene, 4 × CH2Cl2 and 5 × 3CH2Cl2 showed that the Ru22 + core is bridged through the amidate moieties of the two saccharinate ligands, with a head-tail arrangement in complexes 1, 3A and 5, and a head-head arrangement in 4. For complex 3, an equilibrium mixture of the head-head regioisomer 3A and a second species 3b exists in solution. Complexes 1 and 2 are suitable catalysts for the cyclopropanation of nucleophilic alkenes (styrene, cyclohexene and 2-methyl-2-butene) with methyl diazoacetate.
- Buck, Stefan,Maas, Gerhard
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p. 2774 - 2784
(2007/10/03)
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- A practical and controllable enantioselective synthesis of 2-phenyl-1-cyclopropanecarboxylates via a camphor-derived sulfonium ylide
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We have developed a practical and controllable enantioselective synthesis of 2-phenyl-1-cyclopropane-carboxylates via camphor-derived sulfonium ylide. The procedure has many advantages such as cheap starting materials, facile synthetic procedures, good yields, excellent diastereoselectivities and high enantioselectivities. Georg Thieme Verlag Stuttgart.
- Huang, Kun,Huang, Zhi-Zhen
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p. 1621 - 1623
(2007/10/03)
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- Indium-mediated, highly efficient cyclopropanation of olefins using CH 2I2 as methylene transfer reagent
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The indium-mediated, one-pot cyclopropanation of a variety of olefins with methylene iodide proceeds smoothly with excellent yields of products.
- Virender,Jain, Suman L.,Sain, Bir
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- Compounds that modulate PPAR activity and methods of preparation
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This invention discloses compounds that alter PPAR activity. The invention also discloses pharmaceutically acceptable salts of the compounds, pharmaceutically acceptable compositions comprising the compounds or their salts, and methods of using them as therapeutic agents for treating or preventing hyperlipidemia and hypercholesteremia in a mammal. The present invention also discloses methods for making the disclosed compounds.
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- Bis(oxazoline)·copper(I)-catalyzed enantioselective cyclopropanation of cinnamate esters with diazomethane
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Chiral bis(oxazoline)-copper(I) complexes were found to be effective catalysts for the enantioselective cyclopropanation reaction of trans-cinnamate esters exploiting an argon flow mediated diazomethane addition method. After optimization of the catalyst structure, good yields and enantiomeric excesses were obtained with electron-poor methyl cinnamate derivatives. Sterically demanding esters gave lower yields and enantioselectivities. The correlation between the product enantiopurities and the σ+ values of the aromatic para-substituents was shown to be linear in a Hammet-type plot.
- Charette, Andre B.,Janes, Marc K.,Lebel, Helene
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p. 867 - 872
(2007/10/03)
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- A new chiral ruthenium complex for catalytic asymmetric cyclopropanation
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A new chiral ruthenium complex 6, featured with an N,O-mixed polydentate ligand, was synthesized and characterized. This ruthenium complex showed high efficiency in catalytic cyclopropanations of alkenes with diazoacetates. High trans/cis selectivity and enantioselectivity (up to 96%) were achieved with the readily accessible ethyl diazoacetate as the reagent.
- Tang, Wenjun,Hu, Xinquan,Zhang, Xumu
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p. 3075 - 3078
(2007/10/03)
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- Dirhodium(II) tetrakis(perfluoroalkylbenzoates) as partially recyclable catalysts for carbene transfer reactions with diazoacetates
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Three highly fluorinated dirhodium(II) tetrakis(benzoates), [Rh2(O2CRF)4, RF=C6H4-4-C6F13 (3) and C6H3-3,5-di(CnF2n+1) (n=6: 4; n=8: 5)], have been prepared and characterized. Only 4 and 5 are suited for applications in fluorous synthesis due to their excellent solubility in fluorous solvents. They were found to catalyze the following carbenoid reactions of diazo compounds in the fluorous solvents 1,1,2-trichloro-1,2,2-trifluoroethane and perfluoro(methylcyclohexane): cyclopropanation of styrenes using methyl diazoacetate, intermolecular carbene C-H insertion into hexane with methyl diazoacetate, and intramolecular aromatic C-H insertion of an α-diazo-β-ketoester. Except for the second reaction type, the catalyst could be recovered to a high extent by a liquid-liquid extraction (fluorous solvent - dichloromethane) due to its preference for the fluorous solvent. For the cyclopropanation reactions, the recovered catalyst was used in four subsequent reaction/workup cycles without significant loss of activity. In contrast, the catalyst could not be recovered from the carbenoid C-H insertion reaction with hexane; apparently, some by-products of this sluggish reaction, such as carbene dimers and oligomers, caused the deactivation or destruction of the catalyst.
- Endres, Andreas,Maas, Gerhard
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p. 3999 - 4005
(2007/10/03)
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- Calixarenes as ligands for transition-metal catalysts: A bis(calix[4]arene-11,23-dicarboxylato) dirhodium complex
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A novel dirhodium tetracarboxylate complex is described in which two calix[4]arene macrocycles, bridged at the upper rim by a Rh-Rh unit, serve as ligands and whose solid-state structure shows an unusual coordination of a toluene molecule in the axial pos
- Seitz, Juergen,Maas, Gerhard
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p. 338 - 339
(2007/10/03)
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- Highly enantioselective cyclopropanation of styrenes and diazoacetates catalyzed by 3-oxobutylideneaminatocobalt(II) complexes, part 1. Designs of cobalt complex catalysts and the effects of donating ligands
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Highly enantioselective cyclopropanation of styrene derivatives and diazoacetates was effectively catalyzed by reasonably designed 3-oxobutylideneaminatocobalt(II) complexes, whose ligands were prepared from 1,2-dimesitylethyl-enediamine and alkyl 3-oxobutanoates. The steric demand of the diamine unit of the complexes seriously influenced the enantioselectivity, and the ester groups on their side chains somewhat improved the trans-selectivity. Addition of a catalytic amount of N-methylimidazole significantly accelerated the reaction and enhanced the enantioselectivity due to its coordination to the center cobalt atom of the complex as an axial ligand. Alcoholic or aqueous alcoholic solvents were also effective particularly for the cyclopropanation of 1-substituted 1-phenylethylenes to achieve high enantioselectivity in aqueous methanol.
- Ikeno, Taketo,Sato, Mitsuo,Sekino, Hiroyuki,Nishizuka, Asae,Yamada, Tohru
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p. 2139 - 2150
(2007/10/03)
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- Asymmetric inter- and intramolecular cyclopropanation of alkenes catalyzed by chiral ruthenium porphyrins. Synthesis and crystal structure of a chiral metalloporphyrin carbene complex
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Extensive investigations of asymmetric intermolecular cyclopropanation of terminal alkenes with diazoacetates catalyzed by ruthenium porphyrin [Ru(P*)(CO)(EtOH)] (1, H2P* = 5,10,15,20-tetrakis-{(1S,4R,5R,8S)-1,2,3,4,5,6,7,8-octahydro-1,4:5,8- dimethanoanthracene-9-yl}porphyrin) and the application of catalyst 1 to asymmetric intramolecular cyclopropanation of allylic or homoallylic diazoacetates are described. The intermolecular cyclopropanation of styrene and its derivatives with ethyl diazoacetate afforded the corresponding cyclopropyl esters in up to 98% ee with high trans/cis ratios of up to 36 and extremely high catalyst turnovers of up to 1.1 × 104. Examination of the effects of temperature, diazoacetate, solvent, and substituent in the intermolecular cyclopropanation reveals that (i) both enantioselectivity and trans selectivity increase with decreasing temperature, (ii) sterically encumbered diazoacetates N2CHCO2R such as R = But, and donor solvents, such as diethyl ether and tetrahydrofuran, are beneficial to the trans selectivity, and (iii) electron-donating para substituents on styrene accelerate the cyclopropanations, with the log(kx/kH) vs σ+ plot for para-substituted styrenes p-X-C6H4CH=CH2 (X = MeO, Me, Cl, CF3) exhibiting good linearity with a small negative ρ+ value of -0.44 ± 0.09. In the case of intramolecular cyclopropanation, complex 1 promoted the decomposition of a series of allylic diazoacetates to form the cyclopropyl lactones in up to 85% ee, contributing the first efficient metalloporphyrin catalyst for an asymmetric intramolecular cyclopropanation. Both the inter- and intramolecular cyclopropanations were proposed to proceed via a reactive chiral ruthenium carbene intermediate. The enantioselectivities in these processes were rationalized on the basis of the X-ray crystal structures of closely related stable chiral carbene complexes [Ru(P*)(CPh2)] (2) and [Ru(P*)(C(Ph)-CO2CH2CH=CH2)] (3) obtained from reactions of complex 1 with N2CPh2 and N2C(Ph)CO2CH2CH=CH2, respectively.
- Che,Huang,Lee,Li,Lai,Kwong,Teng,Lee,Lo,Peng,Zhou
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p. 4119 - 4129
(2007/10/03)
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- Aza-bis(oxazolines): New chiral ligands for asymmetric catalysis
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diagram presented Aza-bis(oxazolines) are introduced as chiral ligands for asymmetric catalysis combining the advantages of easy availability of bis(oxazolines) and backbone variability of aza-semicorrins. Especially, the title ligands could be attached t
- Glos, Martin,Reiser, Oliver
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p. 2045 - 2048
(2007/10/03)
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- Highly enantioselective cyclopropanation of styrenes with diazoacetates catalyzed by optically active β-ketoiminato cobalt(II) complexes
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The highly enantioselective cyclopropanation of styrenes with diazoacetates was achieved using reasonably designed β-ketoiminato cobalt(II) complex catalysts. In the presence of optically active cobalt(II) complexes derived from optically active 1,2-(2,4,
- Ikeno, Taketo,Sato, Mitsuo,Yamada, Tohru
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p. 1345 - 1346
(2007/10/03)
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- Single-chiral bis(oxazolinyl)pyridine (pybox). Efficiency in asymmetric catalytic cyclopropanation
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Single-chiral bis(oxazolinyl)pyridine ligands were examined as ligands for ruthenium-catalyzed asymmetric catalytic cyclopropanation of olefins: enantioselectivities up to 94% for the trans-cyclopropane were observed.
- Nishiyama, Hisao,Soeda, Norikazu,Naito, Tomonari,Motoyama, Yukihiro
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p. 2865 - 2869
(2007/10/03)
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- Synthesis and evaluation of ruthenium catalysts containing diamine-based ligands in olefin cyclopropanation
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Ruthenium complexes with N-(p-toluenesulfonyl)-diamine ligands were found to be efficient in the catalytic cyclopropanation reaction of olefins with alkyl diazoacetate.
- Simal, Francois,Demonceau, Albert,Noels, Alfred F.
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p. 3493 - 3496
(2007/10/03)
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- Catalytic Asymmetric Synthesis of Cyclopropane Derivatives with Chiral Ruthenium Complexes: Isolation of Intermediate Carbene Complex
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A chiral ruthenium(II)-bis(2-oxazolin-2-yl)pyridine catalyst prepared in situ from optically active bis(2-oxazolin-2-yl)pyridine (Pybox-ip) (2) and [RuCl2(p-cymene)]2 (1) exhibited efficient activity for the asymmetric cyclopropanation (ACP) of styrene and several diazoacetates to give the corresponding trans- and cis-2-phenylcyclopropane-1-carboxylates (3 and 4) in good yields (66-87%). A mixture of 1 and 2 in an atmosphere of ethylene produced the trans-RuCl2(Pybox-ip)(ethylene) complex (5), which also proved to be a powerful catalyst for ACP. The stereoselectivity of the trans- and cis-cyclopropanes were from 90:10 up to 98:2, and their enantioselectivities reached 97%. A catalytic system with 5 could be used for several olefins (6-8) and internal olefins (12 and 13). The non-chiral Ru-Pybox-dihydro catalyst 16 exhibited asymmetric induction with 39% ees of 3 with d- and l-menthyl diazoacetates, and kept a high trans- and cis-stereoselection of 97:3. 2,6-Di-tert-butyl-methylphenyl diazoacetate 17 reacted with the complex 5 to give a stable carbene complex 18, which was characherized by NMR study. The complex 18 exhibited a carbene transfer reaction with styrene at 80°C to give only trans-cyclopropane 3 in 55 %ee.
- Nishiyama
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p. 158 - 164
(2007/10/03)
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- Chiral Ruthenium(II)-Bis(2-oxazolin-2-yl)pyridine Complexes. Asymmetric Catalytic Cyclopropanation of Olefins and Diazoacetates
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A chiral ruthenium(II)-bis(2-oxazolin-2-yl)pyridine catalyst prepared in situ from optically active bis(2-oxazolin-2-yl)pyridine (Pybox-ip) (2) and 2 (1) exhibited efficient activity for the asymmetric cyclopropanation (ACP) of styrene and several diazoacetates to give the corresponding trans- and cis-2-phenylcyclopropane-1-carboxylates (3 and 4) in good yields (66-87percent).A mixture of 1 and 2 in an atmosphere of ethylene produced the trans-RuCl2 (Pybox-ip)(ethylene) complex (5), which also proved to be a poweful catalyst for ACP.The stereoselectivity of the trans- and cis-cyclopropanes were from 90:10 up to 98:2, and their enantioselectivities reached 97percent.A catalytic system with 5 could be used for several olefins and internal olefins.A concerted mechanism of ACP with the Ru-Pybox catalyst was postulated on the basis of the stereospecificity with deuterated styrene.Other substituents, such as ethyl, s-butyl, benzyl, and phenyl on the oxazoline rings of Pybox in place of the isopropyl group were also examined, and were found to exhibit a similar high trans-stereoselection and a high enantioselectivity of the cyclopropane products; ex . with Ru-Pybox-ethyl 91:9 of 3:4 and 82percent ee for 3.The non-chiral Ru-Pybox-dihydro catalyst exhibited asymmetric induction with 39percent ees of 3 with d- and l-menthyl diazoacetates, and kept a high trans- and cis-stereoselection of 97-3.
- Nishiyama, Hisao,Itoh, Yoshiki,Sugawara, Yuji,Matsumoto, Hideki,Aoki, Katsuyuki,Itoh, Kenji
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p. 1247 - 1262
(2007/10/03)
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- Asymmetric Cyclopropanation Using New Chiral Auxiliaries Derived from D-Fructose
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Acetals of α,β-unsaturated aldehydes with 3-O-alkylated derivatives of 1,2-O-isopropylidene-β-D-fructopyranose and 1,2-O-isopropylidene-β-D-psicopyranose, which are readily available from D-fructose, were cyclopropanated with Et2Zn and CH2I2 with good diastereoselectivity.The effects of structure of the acetals on enantioselectivity were examined.
- Kang, Jahyo,Lim, Geun Jho,Yoon, Suk Kyoon,Kim, Moohi Yoo
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p. 564 - 577
(2007/10/02)
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- A Pseudomonas sp. Alcohol Dehydrogenase with Broad Substrate Specificity and Unusual Stereospecificity for Organic Synthesis
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A new alcohol dehydrogenase from Pseudomonas sp. strian PED has been isolated and characterized.The enzyme exhibits a broad substrate specificity, accepting aromatic, cyclic, and aliphatic compounds as substrates.The Km values were determined as 525 μM for NAD and 75 μM for 2-propanol with a specific activity of 36 U/mg.The kinetic mechanism is ordered bi-bi with the cofactor binding first and releasing last.The enzyme transfers the pro-R hydride of NADH to the si face of carbonyl compounds to yield (R) alcohols.Synthetic-scale reductions of a number of representative compounds were carried out in high enentiomeric excess with in situ regeneration of NADH using 2-propanol as the hydride source and the same enzyme as catalyst.
- Bradshaw, Curt W.,Fu, Hong,Shen, Gwo-Jenn,Wong, Chi-Huey
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p. 1526 - 1532
(2007/10/02)
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- Fluoride Ion Promoted Reactions of α-Halo Silanes: Synthesis of Stilbenes, Epoxides, Cyclopropanes, Benzazepines, and Phthalidylisoquinolines
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Reaction of α-halo silanes 1 with CsF in DMF affords stilbenes 5.In the presence of added aldehydes, epoxides 6 are obtained, while with electron-deficient olefins the corresponding cyclopropanes 7 are formed.A similar reaction of 1a with iminium compounds 8 in HMPA leads to 2-phenyl-3-benzazepines 12, whereas 1b or 17 furnishes phthalidylisoquinolines 15.
- Kessar, Satinder V.,Singh, Paramjit,Kaur, Nachhattar Pal,Chawla, Usha,Shukla, Kalpana,et al.
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p. 3908 - 3912
(2007/10/02)
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- 184. Stereoselective Hydrolysis of Substituted Cyclopropanedicarboxylates with Pig Liver Esterase
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The hydrolysis of the meso-cyclopropane-1,2-dicarboxylates 1a-3a, 4, 5a, 6a, and 9, containing various substituents at C(3), and of the rac-3-phenylcyclopropane-1,2-dicarboxylates 7a, 8a, and 10 with pig liver esterase (PLE) is described.The stereoselectivity and absolute configurations of the products were determined.An interpretation of results was attempted on the basis of a recent active-site model for PLE.
- Walser, Paula,Renold, Peter,N'Goka, Victor,Hosseinzadeh, Fatemeh,Tamm, Christoph
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p. 1941 - 1952
(2007/10/02)
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- Reduction and carbonylation of gem-dihalogeno cyclopropanes with iron pentacarbonyl
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Reductive carbonylation of a gem-dibromo cyclopropane to carbomethoxycyclopropane can be achieved with excess Fe(CO)5 in DMF and an added nucleophile such as MeOH or MeONa.
- Reyne, F.,Brun, P.,Waegell, B.
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p. 4597 - 4600
(2007/10/02)
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- Semicorrin Metal Complexes as Enantioselective Catalysts. Part 2. Enantioselective Cyclopropane Formation from Olefins with Diazo Compounds Catalyzed by Chiral (Semicorrinato)copper Complexes)
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Copper complexes of chiral, C2-symmetric semicorrin ligands were found to be efficient catalysts for the cyclopropane formation from olefins with diazo compounds.In the presence of 1 mol-percent of catalyst, alkyl diazoacetates reacted smoothly with termi
- Fritschi, Hugo,Leutenegger, Urs,Pfaltz, Andreas
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p. 1553 - 1565
(2007/10/02)
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- Fluoride Ion Initiated Reactions of α-Halosilanes; Facile Synthesis of Some Stilbenes, Epoxides and Cyclopropanes
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Treatment of α-halosilanes (1) with CsF in DMF furnishes stilbenes (3); in the presence of added aldehydes epoxides (5) are obtained while with electron deficient olefins the corresponding cyclopropanes (6) are formed.
- Kessar, Satinder V.,Singh, Paramjit,Venugopal, D.
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p. 605 - 606
(2007/10/02)
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- Stereochemical Analysis of an Aromatic Triplet Di-?-methane Rearrangement
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It is shown that (-)-(S)-N,N-dimethyl-2-(1'-methylallyl)aniline((-)-(S)-4), on direct irradiation in MeCN at 20 deg C, undergoes in its lowest-lying triplet state an aromatic di-?-methane (ADPM) rearrangement to yield (-)-(1'R,2'R)- and (+)-(1'R,2'S)-N,N-dimethyl-2-(2'-methylcyclopropyl)aniline((-)trans- and (+)-cis-7) in an initial trans/cis ratio of 4.71 +/- 0.14 and in optical yields of 28.8 +/- 5.2percent and 15 +/- 5percent, respectively.The ADPM rearrangement of (-)-(S)-4 to the trans- and cis-configurated products occurs with preponderance of the path leading to retention of configuration at the pivot atom (C(1') in the reactant and C(2') in the products) for (-)-trans-7 and to inversion of configuration for (+)-cis-7, respectively.The results can be rationalised by assuming reaction paths which involve the occurence of discrete 1,4- and 1,3-diradicals (cf.Schemes 10, 12, and 13).A general analysis of such ADPM rearrangements which allows the classification of these photochemical reaction in terms of borderline cases is presented (Scheme 14).It is found that the optical yields in these 'step-by-step' rearrangements are determined by the first step, i.e. by the disrotatory bond formation between C(2) of the aromatic moiety and C(2') of the allylic side chain leading to the generation of the 1,4-diradicals.Moderation of the optical yields can occur in the ring closure of the 1,3-diradicals to the final products, which may take place with different trans/cis-ratios for the individual 1,3-diradicals.Compounds (-)-trans-7 as well as (+)-cis-7 easily undergo the well-known photochemical trans/cis-isomerization.It mainly leads to racemization.However, a small part of the molecules shows trans/cis-isomerization with inversion of configuration at C(1'), which is best explained by a photochemical cleavage of the C(1')-C(3') bond.
- Scholl, Bernhard,Hansen, Hans-Juergen
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p. 1936 - 1958
(2007/10/02)
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- Deprotonation and Diastereoselective Alkylation of Methyl Cyclopropanecarboxylates
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Using model compounds it is demonstrated when deprotonation of methyl cyclopropanecarboxylates leads to ester condensation products and when alkylation of the ester enolate can be performed.Under certain structural conditions (steric and electronic effect
- Reichelt, Ingrid,Reissig, Hans-Ulrich
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p. 3895 - 3914
(2007/10/02)
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