- Hydroxy and ether functionalized dithiolanes: Models for the active site of the [FeFe] hydrogenase
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In attempt to synthesize suitable [FeFe] hydrogenase model complexes, 2-methoxypropane-1,3-dithiole and 4-methyl-4-hydroxy-1,2-dithiolane were reacted with Fe3(CO)12 to give the respective complexes [Fe 2(CO)6(H3COCH(CH2S)2)] and [Fe2(CO)6(HOC(CH3)(CH2S) 2)]. The compounds were characterized by 1H and 13C NMR spectroscopy, mass spectrometry and elemental analysis. In addition, their electrochemical properties were investigated by cyclic voltammetry and compared with that of [Fe2(CO) 6(HOC(CH2S)2)] known from literature.
- Apfel, Ulf-Peter,Kowol, Christian R.,Kloss, Florian,G?rls, Helmar,Keppler, Bernhard K.,Weigand, Wolfgang
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- Infrared and nuclear magnetic resonance spectroscopic studies of the structure and dynamics of allylic magnesium compounds
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The infrared spectra of allyl- and methallyl-d2-magnesium bromides have two double bond stretching bands, corresponding to C=CH2 and C=CD2 groups in equilibrating allylic isomers. The methylene resonances in the 13C NMR spectra of allylmagnesium bromide and chloride and methallylmagnesium bromide are broadened at low temperatures by an exchange process which appears to be the interconversion between the classical unsymmetrical allylic structures. Analogous changes are seen in the spectrum of 1,3-dimethylallylmagnesium chloride and in the proton NMR spectrum of allylmagnesium bromide. Rate constants and activation parameters for the exchange have been determined from the line broadenings. Unlike the Grignard reagent, the methylene resonances of diallylmagnesium in tetrahydrofuran are not significantly broadened at reduced temperature, and the deuterated reagent does not have two distinct double bond stretching bands in the IR spectrum.
- Hill, E. Alexander,Boyd, Winston A.,Desai, Hemnalini,Darki, Amir,Bivens, Lymel
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- Pd-Catalyzed Asymmetric Acyl-Carbamoylation of an Alkene to Construct an α-Quaternary Chiral Cycloketone
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Herein, we report the palladium-catalyzed asymmetric acyl-carbamoylation of an alkene by employing thioesters as the acyl electrophiles and t-BuNC as the carbamoyl reagent, affording an α-quaternary chiral cycloketone in synthetically useful yields with excellent enantioselectivity. The reaction proceeded via asymmetric 1,2-migratory insertions of acyl-Pd into alkenes and subsequent migratory insertion of isocyanides into C(sp3)-PdII. The product could be diversified to some valuable skeletons with retention of enantiopurity, demonstrating the synthetic utility of this protocol.
- Liu, Min,Wang, Xing,Guo, Ziqiong,Li, Hanyuan,Huang, Wei,Xu, Hui,Dai, Hui-Xiong
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supporting information
p. 6299 - 6304
(2021/08/30)
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- Regiospecific Synthesis of Calcium-Independent Daptomycin Antibiotics using a Chemoenzymatic Method
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Daptomycin (DAP) is a calcium (Ca2+)-dependent FDA-approved antibiotic drug for the treatment of Gram-positive infections. It possesses a complex pharmacophore hampering derivatization and/or synthesis of analogues. To mimic the Ca2+-binding effect, we used a chemoenzymatic approach to modify the tryptophan (Trp) residue of DAP and synthesize kinetically characterized and structurally elucidated regiospecific Trp-modified DAP analogues. We demonstrated that the modified DAPs are several times more active than the parent molecule against antibiotic-susceptible and antibiotic-resistant Gram-positive bacteria. Strikingly, and in contrast to the parent molecule, the DAP derivatives do not rely on calcium or any additional elements for activity.
- Mupparapu, Nagaraju,Lin, Yu-Hsin Cindy,Kim, Tae Ho,Elshahawi, Sherif I.
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supporting information
p. 4176 - 4182
(2021/02/01)
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- Copper-Catalyzed Enantiotopic-Group-Selective Allylation of gem-Diborylalkanes
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We report a copper-catalyzed enatiotopic-group-selective allylation of gem-diborylalkanes with allyl bromides. The combination of copper(I) bromide and H8-BINOL derived phosphoramidite ligand proved to be the most effective catalytic system to provide various enantioenriched homoallylic boronate esters, containing a boron-substituted stereogenic center that is solely derived from gem-diborylalkanes, in good yields with high enantiomeric ratios under mild conditions. Experimental and theoretical studies have been conducted to elucidate the reaction mechanism, revealing how the enatiotopic-group-selective transmetalation of gem-diborylalkanes with chiral copper complex occurs to generate chiral α-borylalkyl-copper species for the first time. Additional synthetic applications to the synthesis of various chiral building blocks are also included.
- Kim, Minjae,Park, Bohyun,Shin, Minkyeong,Kim, Suyeon,Kim, Junghoon,Baik, Mu-Hyun,Cho, Seung Hwan
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supporting information
p. 1069 - 1077
(2021/01/25)
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- Nickel-Catalyzed Asymmetric Reductive 1,2-Carboamination of Unactivated Alkenes
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Starting from diverse alkene-tethered aryl iodides and O-benzoyl-hydroxylamines, the enantioselective reductive cross-electrophilic 1,2-carboamination of unactivated alkenes was achieved using a chiral pyrox/nickel complex as the catalyst. This mild, modular, and practical protocol provides rapid access to a variety of β-chiral amines with an enantioenriched aryl-substituted quaternary carbon center in good yields and with excellent enantioselectivities. This process reveals a complementary regioselectivity when compared to Pd and Cu catalysis.
- He, Jun,Xue, Yuhang,Han, Bo,Zhang, Chunzhu,Wang, You,Zhu, Shaolin
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supporting information
p. 2328 - 2332
(2020/01/08)
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- Silver-promoted cascade radical cyclization of γ,δ-unsaturated oxime esters with P(O)H compounds: synthesis of phosphorylated pyrrolines
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A cascade radical cyclization was realized for the first silver-promoted imino-phosphorylation of γ,δ-unsaturated oxime esters, which provided a step-economical and redox-neutral route to access a variety of phosphorylated pyrrolines in good to excellent yields. Moreover, a new bulky trivalent phosphine ligand with a pyrroline motif was obtained through a deoxidation process.
- Chen, Chen,Bao, Yinwei,Zhao, Jinghui,Zhu, Bolin
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supporting information
p. 14697 - 14700
(2019/12/11)
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- Organic base-catalysed solvent-tuned chemoselective carbotrifluoromethylation and oxytrifluoromethylation of unactivated alkenes
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An unprecedented and efficient organic base-catalysed highly chemoselective carbo- and oxytrifluoromethylation of unactivated alkenes with Togni's reagent was developed. The switchable chemoselectivity was tuned by simply changing the organic base catalyst and solvent. Mechanistic studies indicated that a radical cyclization pathway for carbotrifluoromethylation in DMSO and a carbocation pathway for oxytrifluoromethylation in DCE were probably involved.
- Yang, Ning-Yuan,Li, Zhong-Liang,Ye, Liu,Tan, Bin,Liu, Xin-Yuan
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supporting information
p. 9052 - 9055
(2016/07/21)
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- Catalytic enantioselective iodoaminocyclization of hydrazones
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The first catalytic enantioselective iodoaminocyclization of β,γ-unsaturated hydrazones has been developed with the help of a trans-1,2-diaminocyclohexane-derived bifunctional thiourea catalyst and allows for the direct access to δ2-pyrazolines containing a quaternary stereogenic center in high yield with good enantioselectivity (up to 95% yield and 95:5 er).
- Tripathi, Chandra Bhushan,Mukherjee, Santanu
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supporting information
p. 3368 - 3371
(2014/07/08)
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- Oxidative bromination of alkenes mediated with nitrite in ionic liquids
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The oxidative bromination of C2-C8 alkenes with HBr-NaNO2-O2 in solutions of BMImBr, HMImBr or BMImBF 4 containing 16-28 wt% H2O was studied using volumetric method, GC-MS analysis, 14N NMR and UV-VIS spectroscopy. The optimal conditions to conduct the reaction at high selectivity for 1,2-dibromoalkanes in BMImBr were determined. The composition of ionic liquid affects the catalytic performance. Although in BMImBF4 the reaction runs with equal rate as in bromide ionic liquid, the fraction of bromohydrin in the reaction products increases to 20 %. Generated from NaNO2, NOx operated as a catalyst in the oxidation of Br- and was oxidized to catalytically inert NO3 - anions when complete conversion of HBr was attained. Graphical Abstract: Oxidative bromination of alkenes [Figure not available: see fulltext.]
- Kuznetsova, Lidia I.,Kuznetsova, Nina I.,Zudin, Vladimir N.,Utkin, Viktor A.,Trebushat, Dmitry V.,Fedotov, Martin A.,Larina, Tatyana V.
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p. 1499 - 1506,8
(2014/11/08)
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- Synthesis of 3-aza-bicyclo[3.1.0]hexan-2-one derivatives via gold-catalyzed oxidative cyclopropanation of N -allylynamides
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N-Allylynamides with various functional groups and different substitution patterns can be converted into 3-aza-bicyclo[3.1.0]hexan-2-one derivatives in moderate to high yield using IMesAuCl/AgBF4 as the catalyst and pyridine N-oxide as the oxidant. A noncarbene mediated approach is proposed as the mechanism.
- Wang, Kai-Bing,Ran, Rui-Qiao,Xiu, Shi-Dong,Li, Chuan-Ying
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supporting information
p. 2374 - 2377
(2013/06/27)
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- Synthetic study on tetrapetalones: Stereoselective cyclization of N-acyliminium ion to construct substituted 1-benzazepines
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The synthesis of the tetracyclic core of complex antibiotic tetrapetalones has been achieved In three steps starting from the simple Intermediate γ-hydroxy amide, which can be accessed through a high-yielding six-step sequence. The successful synthesis relies on a novel strategy based on the N-acyliminium ion cyclizatlon.
- Cheng, Li,Xlnyu, L.I. And,Ran, Hong
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supporting information; experimental part
p. 4036 - 4039
(2009/12/09)
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- One-pot synthesis of aryl sulfones from alcohols
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A one-pot synthesis of aryl sulfones from primary alcohols is described. Alcohols were treated with N-bromosuccinimide and triphenylphosphine, followed by addition of sodium arenesulfinate with a catalytic amount of tetrabutylammonium iodide to afford the aryl sulfones in good to high yields.
- Murakami, Teiichi,Furusawa, Kiyotaka
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p. 479 - 482
(2007/10/03)
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- Process for producing allyl bromides
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An improved process for producing allyl bromides by halogen exchange by reaction of an allyl chloride, with a metal bromide, wherein the reaction is conducted in an aprotic polar solvent. The allyl bromides obtained by the process of the invention are useful as intermediates for producing medicines, agricultural chemicals, dyes, and the like.
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- Reaction of Trialkyl Orthoformates with the Aluminium Derivatives of Some α-Unsaturated Bromides. Preparation of β-Unsaturated Acetals
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Die Aluminium-Derivate 2, 4, und 7 α-ungesaettigter Bromide, dargestellt in Ether, sind sehr reaktionsfaehig gegenueber Trialkylorthoformaten.Mit Hilfe dieser Reaktion, durchgefuehrt bei -80 deg C, koennen auf einfache Weise β-ungesaettigte Acetale 3, 5, bzw. 8 dargestellt werden.
- Picotin, Gerard,Miginiac, Philippe
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p. 1725 - 1730
(2007/10/02)
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- SELECTIVITIES OF pi - AND sigma -SUCCINIMIDYL RADICALS IN SUBSTITUTION AND ADDITION REACTIONS. APPENDIX: RESPONSE TO WALLING, EL-TALIAWI, AND ZHAO.
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A new method for studies of pi -succinimidyl (S// pi ) radicals is described, one that makes possible the study of reactions of this radical with a variety of substrates not accessible by the use of Br//2-NBS. NBS systems containing BrCCl//3 at mole fractions greater than 0. 3 show all the characteristics associated with S// pi behavior, and they function in the presence of olefins which serve as Br//2 scavengers. If CCl//4 is substituted for BrCCl//3, the system is clearly S// sigma . The S// pi behavior is contrasted with S// sigma and Br multiplied by (times) reactivities for H abstractions from a variety of substrates and for additions to tert-butylethylene, isobutylene, and 1,3-butadiene. In early-transition-state systems, for H transfer, the strength of the bond being broken and the strength of the bond being made are not the major factors in determining reactivities. The behavior in late-transition-state systems is influenced by both bond strengths. The S// pi radical shows intermediate behavior. These conclusions are supported by primary deuterium isotope effects for methylene chloride and chlororoform. The Appendix addresses a number of questions raised by the preliminary study of NBS reactions by Walling et al.
- Skell,Tlumak,Seshadri
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p. 5125 - 5131
(2007/10/02)
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- Diastereoselective α Allylation of Secondary and Tertiary Thioamides via Thio-Claisen Rearrangement. A Structural Proof of Z Secondary Thioamide Dianions and Z Tertiary Thioamide Anions
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Highly diastereoselective α allylation of secondary and tertiary thioamides is achieved by making use of thio-Claisen rearrangement.From the correlation between the diastereoselectivities in products and the structures of allylating agents, the Z structures of secondary thioamide dianion (ca. 100percent Z) and tertiary thioamide anion (>97percent Z) are concluded.
- Tamaru, Y.,Furukawa, Y.,Mizutani, M.,Kitao, O.,Yoshida, Z.
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p. 3631 - 3639
(2007/10/02)
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- SYNTHESE RADICALAIRE D'ANALGESIQUES POTENTIELS: ARYL-4 PIPERIDINES SUBSTITUEES EN 2 ET BENZOMORPHANES
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The synthesis of a series of 3-aryl 5-hexenyl amines and the cyclisations of the corresponding N-chloroamines are described.When the ring closure results from the amino radical addition to the ethylenic double bond, 2-chloromethyl 4-phenyl piperidines are obtained.These compounds lead by intramolecular Friedel-Crafts reaction to varied substituted 6,7-benzomorphanes.When the phenyl ring is substituted with a methoxyl group, the cyclisation proceeds via homolytic aromatic substitution and 4-allyl tetrahydroquinolines are formed.
- Stella, L.,Raynier, B.,Surzur, J. M.
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p. 2843 - 2854
(2007/10/02)
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