- Copper-catalyzed hydroallylation of allenes employing hydrosilanes and allyl chlorides
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The hydroallylation of allenes was developed by employing a hydrosilane and allyl chlorides in the presence of a copper catalyst. The reaction provided (E)-1,5-dienes mainly in good to high yields.
- Fujihara, Tetsuaki,Yokota, Ken,Terao, Jun,Tsuji, Yasushi
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Read Online
- Trifluoromethylthiolation of 1, 3- and 1, 4-cyclohexadienes
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Treatment of 1, 3-cyclohexadiene with CF3SCl at -80 furnishes 15 compounds. All but the two dimerized adducts arise from the free radical catalyzed addition of CF3S and Cl radicals to carbon-carbon double bonds. One dimerized product
- Rohrbaugh,Durst,Longo,Munavalli
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Read Online
- A mild method for the replacement of a hydroxyl group by halogen: 3. the dichotomous behavior of α-haloenamines towards allylic and propargylic alcohols
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A study of the deoxyhalogenation of allylic and propargylic alcohols with tetramethyl-α-halo-enamines is reported. Primary allylic and primary and secondary propargylic alcohols gave the corresponding halides in high yields. Secondary allylic and propargylic alcohols yielded the corresponding secondary halides but the reaction also produced some rearranged primary halides (I > Br > Cl). The reactions with tertiary allylic and tertiary propargylic alcohols gave several products and was therefore of little synthetic value. However, the addition of triethylamine to the reaction mixture or the use of lithium alkoxide instead of alcohol brought about a major change of the course of the reaction which led to amides carrying an allyl or an allenyl group at C2. This was shown to result from a Claisen-Eschenmoser rearrangement of an intermediate α-allyloxy- or propargyloxy-enamine.
- Munyemana, Fran?ois,Patiny, Luc,Ghosez, Léon
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- Guanidine–Copper Complex Catalyzed Allylic Borylation for the Enantioconvergent Synthesis of Tertiary Cyclic Allylboronates
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An enantioconvergent synthesis of chiral cyclic allylboronates from racemic allylic bromides was achieved by using a guanidine–copper catalyst. The allylboronates were obtained with high γ/α regioselectivities (up to 99:1) and enantioselectivities (up to 99 % ee), and could be further transformed into diverse functionalized allylic compounds without erosion of optical purity. Experimental and DFT mechanistic studies support an SN2′ borylation process catalyzed by a monodentate guanidine–copper(I) complex that proceeds through a special direct enantioconvergent transformation mechanism.
- Ge, Yicen,Cui, Xi-Yang,Tan, Siu Min,Jiang, Huan,Ren, Jingyun,Lee, Nicholas,Lee, Richmond,Tan, Choon-Hong
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supporting information
p. 2382 - 2386
(2019/02/01)
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- Aliphatic C-H Bond Halogenation by Iron(II)-α-Keto Acid Complexes and O2: Functional Mimicking of Nonheme Iron Halogenases
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α-Ketoglutarate-dependent nonheme halogenases catalyze the halogenation of aliphatic C-H bonds in the biosynthesis pathway of many natural products. An iron(IV)-oxo-halo species has been established as the active oxidant in the halogenation reactions. With an objective to emulate the function of the nonheme halogenases, two iron(II)-α-keto acid complexes, [(phdpa)Fe(BF)Cl] (1) and [(1,4-tpbd)Fe2(BF)2Cl2] (2) (where phdpa = N,N-bis(2-pyridylmethyl)aniline, 1,4-tpbd = N,N,N′,N'-tetrakis(2-pyridylmethyl)benzene-1,4-diamine, and BF = benzoylformate), have been prepared. The iron complexes are capable of carrying out the oxidative halogenation of aliphatic C-H bonds using O2 as the terminal oxidant. Although the complexes are not selective toward C-H bond halogenation, they are the only examples of nonheme iron(II)-α-keto acid complexes mimicking the activity of nonheme halogenases. The dinuclear complex (2) exhibits enhanced reactivity toward C-H bond halogenation/hydroxylation.
- Jana, Rahul Dev,Sheet, Debobrata,Chatterjee, Sayanti,Paine, Tapan Kanti
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p. 8769 - 8777
(2018/08/17)
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- Mechanistic Studies on a Cu-Catalyzed Asymmetric Allylic Alkylation with Cyclic Racemic Starting Materials
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Mechanistic studies on Cu-catalyzed asymmetric additions of alkylzirconocene nucleophiles to racemic allylic halide electrophiles were conducted using a combination of isotopic labeling, NMR spectroscopy, kinetic modeling, structure-activity relationships, and new reaction development. Kinetic and dynamic NMR spectroscopic studies provided insight into the oligomeric Cu-ligand complexes, which evolve during the course of the reaction to become faster and more highly enantioselective. The Cu-counterions play a role in both selecting different pathways and in racemizing the starting material via formation of an allyl iodide intermediate. We quantify the rate of Cu-catalyzed allyl iodide isomerization and identify a series of conditions under which the formation and racemization of the allyl iodide occurs. We developed reaction conditions where racemic allylic phosphates are suitable substrates using new phosphoramidite ligand D. D also allows highly enantioselective addition to racemic seven-membered-ring allyl chlorides for the first time.1H and2H NMR spectroscopy experiments on reactions using allylic phosphates showed the importance of allyl chloride intermediates, which form either by the action of TMSCl or from an adventitious chloride source. Overall these studies support a mechanism where complex oligomeric catalysts both racemize the starting material and select one enantiomer for a highly enantioselective reaction. It is anticipated that this work will enable extension of copper-catalyzed asymmetric reactions and provide understanding on how to develop dynamic kinetic asymmetric transformations more broadly.
- Rideau, Emeline,You, Hengzhi,Sidera, Mireia,Claridge, Timothy D. W.,Fletcher, Stephen P.
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supporting information
p. 5614 - 5624
(2017/04/27)
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- Chlorohydrination of allyl chloride with HCl and H2O2 catalyzed by hollow titanium silicate zeolite to produce dichloropropanol
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Overall, over 95% of epichlorohydrin is industrially manufactured via the chlorohydrination route with hazardous Cl2 as a reagent, which brings serious operation and pollution problems. Herein, we describe a novel Cl2-free process for the synthesis of dichloropropanols from allyl chloride with H2O2 and HCl catalyzed by hollow titanium silicate zeolite under mild conditions. A high conversion and overall dichloropropanol selectivity exceeding 95% are simultaneously achieved, and the heterogeneous catalyst is highly stable and amenable for reuse. Comprehensive experimental and spectroscopic data suggest that the Lewis acidity of the framework Ti species has a synergistic effect with the Br?nsted acidity of HCl that promotes the epoxidation of allyl chloride and the ring opening of the epoxy groups.
- Peng, Xinxin,Xia, Changjiu,Lin, Min,Yuan, Hui,Zhu, Bin,Zhang, Yao,Wang, Baorong,Shu, Xingtian
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supporting information
p. 1221 - 1225
(2017/08/15)
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- Chemoenzymatic Total Synthesis of Hydromorphone by an Oxidative Dearomatization/Intramolecular [4 + 2] Cycloaddition Sequence: A Second-Generation Approach
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A second-generation approach to the synthesis of hydromorphone by oxidative dearomatization/Diels-Alder cycloaddition was investigated. Detailed analysis of the stereochemical outcome of the [4 + 2] cycloaddition was performed first on a truncated model system as well as on the material leading to ent-hydromorphone. The stereochemical assignments were made by NMR and X-ray methods. The second-generation synthesis of hydromorphone was completed in both enantiomeric series. Improvements in the dearomatization conditions were attained using hypervalent iodine reagents instead of Pb(OAc)4. Electrochemical methods of oxidative dearomatization were also investigated. New conditions enabling the rearomatization of ring A from the methoxyketal were developed, and a formal synthesis of the natural enantiomer of hydromorphone was completed. Experimental and spectral data are provided for all new compounds.
- Rycek, Lukas,Hayward, John J.,Latif, Marwa Abdel,Tanko, James,Simionescu, Razvan,Hudlicky, Tomas
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p. 10930 - 10941
(2016/11/28)
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- Hydroxylation versus Halogenation of Aliphatic C?H Bonds by a Dioxygen-Derived Iron–Oxygen Oxidant: Functional Mimicking of Iron Halogenases
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An iron–oxygen intermediate species generated in situ in the reductive activation of dioxygen by an iron(II)–benzilate complex of a monoanionic facial N3ligand, promoted the halogenation of aliphatic C?H bonds in the presence of a protic acid and a halide anion. An electrophilic iron(IV)–oxo oxidant with a coordinated halide is proposed as the active oxidant. The halogenation reaction with dioxygen and the iron complex mimics the activity of non-heme iron halogenases.
- Chatterjee, Sayanti,Paine, Tapan Kanti
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supporting information
p. 7717 - 7722
(2016/07/07)
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- Trihaloisocyanuric Acid/Triphenylphosphine: An Efficient System for Regioselective Conversion of Epoxides into Vicinal Halohydrins and Vicinal Dihalides under Mild Conditions
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A new synthetic method has been developed for the regioselective conversion of epoxides to vicinal chloro-/bromohydrins and vicinal dihalides by reaction with the system trihaloisocyanuric acid/tri?phenylphosphine in acetonitrile under mild and neutral conditions. The reactions proceed smoothly in high yield at room temperature and at reflux, respectively, over a short time.
- De Andrade, Vitor S. C.,De Mattos, Marcio C. S.
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p. 1381 - 1388
(2016/05/19)
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- Catalytic, stereospecific syn-dichlorination of alkenes
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As some of the oldest organic chemical reactions known, the ionic additions of elemental halogens such as bromine and chlorine to alkenes are prototypical examples of stereospecific reactions, typically delivering vicinal dihalides resulting from anti-addition. Although the invention of enantioselective variants is an ongoing challenge, the ability to overturn the intrinsic anti-diastereospecificity of these transformations is also a largely unsolved problem. Here, we describe the first catalytic, syn-stereospecific dichlorination of alkenes, employing a group transfer catalyst based on a redox-active main group element (selenium). With diphenyl diselenide (PhSeSePh) (5amol%) as the pre-catalyst, benzyltriethylammonium chloride (BnEt 3 NCl) as the chloride source and an N-fluoropyridinium salt as the oxidant, a wide variety of functionalized cyclic and acyclic 1,2-disubstituted alkenes, including simple allylic alcohols, deliver syn-dichlorides with exquisite stereocontrol. This methodology is expected to find applications in streamlining the synthesis of polychlorinated natural products such as the chlorosulfolipids.
- Cresswell, Alexander J.,Eey, Stanley T.-C.,Denmark, Scott E.
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p. 146 - 152
(2015/03/04)
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- Rhodium-catalyzed alkene hydrosilylation via a hydride shuttle process by diene ligands: Dramatic enhancement of regio- and diastereoselectivity
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A cooperative ligand-assisted, Rh-catalyzed intramolecular alkene hydrosilylation of homoallylic silyl ethers (1) was developed to provide 1,3-trans-oxasilacyclopentanes (trans-2) in a highly regio- and diastereoselective manner. The modification of metal-ligand architecture employing an inner-sphere functional diene ligand (1,3-cyclohexadiene) and a supporting phosphine ligand (BINAP) was identified as responsible for dramatic enhancement of selectivities. Mechanistic details of a diene ligand-mediated hydride shuttle process are presented as the potential mechanistic driving force behind the high level of the selectivities.
- Hua, Yuanda,Nguyen, Hiep H.,Trog, Gabriela,Berlin, Adam S.,Jeon, Junha
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supporting information
p. 5890 - 5895
(2015/03/30)
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- Formation of iron(III) meso-chloro-isoporphyrin as a reactive chlorinating agent from oxoiron(IV) porphyrin π-cation radical
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Iron(III) isoporphyrin, a tautomer of porphyrin with a saturated meso carbon, is one of the isoelectronic forms of oxoiron(IV) porphyrin π-cation radical, which is known as an important reactive intermediate of various heme enzymes. The isoporphyrin has been believed to be incapable of catalyzing oxygenation and oxidation reactions. Here, we report that an oxoiron(IV) porphyrin π-cation radical can be converted to iron(III) meso-chloro- isoporphyrin in the presence of trifluoroacetic acid and chloride ion. More importantly, this study shows the first evidence that iron(III) meso-chloro-isoporphyrin is an excellent reactive agent for chlorinating aromatic compounds and olefins. The results of this study suggest that the mechanism involves electrophilic chlorination of substrate with iron(III) meso-chloro-isoporphyrin.
- Cong, Zhiqi,Kurahashi, Takuya,Fujii, Hiroshi
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supporting information; experimental part
p. 4469 - 4472
(2012/04/23)
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- Pyridine-assisted chlorinations and oxidations by palladium(IV)
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The reactivity of the bis-NHC complex LPdIVCl4 (L = κ2-[R-NHCCH2NHC-R] with R = C14H 29) in chlorinations and oxidations of organic substrates was considerably increased in the presence of pyridine. For alkene chlorinations, this effect was due to the in situ formation of highly reactive LPd IVCl3(py)+, which was able to transfer Cl + to the C=C bond in a ligand-mediated process (devoid of π complexation), which did not require py dissociation. The enhanced reactivity in the presence of pyridine also extended to the oxidation of secondary and benzylic alcohols under mild conditions in a reaction where py served as a base, broadening the known scope of reactivity for PdIV complexes. LPdIVCl3(py)+ could be formed from Cl -/py exchange or from the oxidation of LPdIICl(py) + by Cl2. Taking advantage of the enhanced reactivities that pyridine coordination imparted on both PdII and PdIV complexes allowed for the catalytic chlorination of styrene with LPd IVCl4 as a sacrificial oxidant, thereby establishing the principal feasibility of PdII/PdIV catalyses that obviates PdII activations of the substrate.
- McCall, A. Scott,Kraft, Stefan
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scheme or table
p. 3527 - 3538
(2012/06/16)
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- Catalytic phosphorus(V)-mediated nucleophilic substitution reactions: Development of a catalytic appel reaction
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Catalytic phosphorus(V)-mediated chlorination and bromination reactions of alcohols have been developed. The new reactions constitute a catalytic version of the classical Appel halogenation reaction. In these new reactions oxalyl chloride is used as a consumable stoichiometric reagent to generate the halophosphonium salts responsible for halogenation from catalytic phosphine oxides. Thus, phosphine oxides have been transformed from stoichiometric waste products into catalysts and a new concept for catalytic phosphorus-based activation and nucleophilic substitution of alcohols has been validated. The present study has focused on a full exploration of the scope and limitations of phosphine oxide catalyzed chlorination reactions as well as the development of the analogous bromination reactions. Further mechanistic studies, including density functional theory calculations on proposed intermediates of the catalytic cycle, are consistent with a catalytic cycle involving halo- and alkoxyphosphonium salts as intermediates.
- Denton, Ross M.,An, Jie,Adeniran, Beatrice,Blake, Alexander J.,Lewis, William,Poulton, Andrew M.
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experimental part
p. 6749 - 6767
(2011/10/02)
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- Hydrocarbon chlorination promoted by manganese and iron complexes with methylated derivatives of bis(2-pyridylmethyl)-1,2-ethanediamine
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Non-heme iron halogenases, such as SyrB2 and CytC3, catalyze the regioselective chlorination and bromination of aliphatic C-H bonds. Reported here is the hydrocarbon chlorination promoted by manganese and iron complexes with methylated derivatives of bis(2-pyridylmethyl)-1,2-ethanediamine (bispicen). The reactions between these coordination compounds and meta-chloroperbenzoic acid generate oxidants capable of oxidizing weak C-H bonds to C-Cl bonds. This chemistry is regioselective, with a strong preference for activating C-H bonds on secondary carbons over weaker C-H bonds on tertiary carbons. The reactivity is consistent with the methyl groups on the ligands preventing more sterically encumbered substrates from accessing the reactive portions of a [MIV(LMen)(O)Cl2] oxidant. The iron compounds promote more hydrocarbon chlorination than their manganese analogs.
- Goldsmith, Christian R.,Coates, Cristina M.,Hagan, Kenton,Mitchell, Casey A.
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body text
p. 24 - 30
(2011/04/22)
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- Bis- N -heterocyclic carbene palladium(IV) tetrachloride complexes: Synthesis, reactivity, and mechanisms of direct chlorinations and oxidations of organic substrates
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This Article describes the preparation and isolation of novel octahedral CH2-bridged bis-(N-heterocyclic carbene)palladium(IV) tetrachlorides of the general formula LPdIVCl4 [L = (NHC)CH 2(NHC)] from LPdIICl2 and Cl2. In intermolecular, nonchelation-controlled transformations LPdIVCl 4 reacted with alkenes and alkynes to 1,2-dichlorination adducts. Aromatic, benzylic, and aliphatic C-H bonds were converted into C-Cl bonds. Detailed mechanistic investigations in the dichlorinations of alkenes were conducted on the 18VE PdIV complex. Positive solvent effects as well as kinetic measurements probing the impact of cyclohexene and chloride concentrations on the rate of alkene chlorination support a PdIV-Cl ionization in the first step. Product stereochemistry and product distributions from various alkenes also support Cl+-transfer from the pentacoordinated PdIV-intermediate LPdIVCl 3+ to olefins. 1-Hexene/3-hexene competition experiments rule out both the formation of π-complexes along the reaction coordinate as well as in situ generated Cl2 from a reductive elimination process. Instead, a ligand-mediated direct Cl+-transfer from LPd IVCl3+ to the π-system is likely to occur. Similarly, C-H bond chlorinations proceed via an electrophilic process with in situ formed LPdIVCl3+. The presence of a large excess of added Cl- slows cyclohexene chlorination while the presence of stoichiometric amounts of chloride accelerates both PdIV-Cl ionization and Cl+-transfer from LPdIVCl3 +. 1H NMR titrations, T1 relaxation time measurements, binding isotherms, and Job plot analysis point to the formation of a trifurcated Cl-...H-C bond in the NHC-ligand periphery as a supramolecular cause for the accelerated chemical events involving the metal center.
- McCall, A. Scott,Wang, Hongwang,Desper, John M.,Kraft, Stefan
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supporting information; experimental part
p. 1832 - 1848
(2011/04/15)
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- Rate coefficients and products for gas-phase reactions of chlorine atoms with cyclic unsaturated hydrocarbons at 298 K
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Rate coefficients for the reaction of Cl atoms with cycloalkenes have been determined using the relative rate method, at 298 K and atmospheric pressure of N2. Reference molecule was n -hexane, and the concentrations of the organics were followed by gas chromatographic analysis. Cl atoms were prepared by photolysis of trichloroacetyl chloride at 254 nm. The relative rates of reactions of Cl atoms with cycloalkenes, with, respect to M-hexane, are measured as 1.12 ±0.38, 1.31 ±0.14, and 1.69±0.18forcyclopentene, cyclohexene, and cycloheptene, respectively. Considering the absolute value of the rate coefficient of the reaction of Cl atom with n-hexane as 3.03 ± 0.06 × 10-10 cm3 molecule-1 s -1, the rate coefficient values for cyclopentene, cyclohexene, and cycloheptene are calculated, to be (3.39 ± 1.08) × 10 -10, (3.97 ±0.43) × 10-10, and (5.12 ± 0.55) × 10-10 cm3 molecule-1 S -1', respectively. The experiments for each, molecule were repeated six to eight times, and the slopes and the rate coefficients given above are the average values of these measurements, and the quoted error includes 2σ as well as all other uncertainties in the measurement and calculations. The rate coefficient increases linearly with the number of carbon atoms, with an increment per additional CH2 group being (8.7 ± 1.6) × 11-12 cm3 molecule-1 s-1. Chloroketones and chloroalcohols, along with unsaturated, ketones and alcohols, were found to be the major products of Cl-atom-initiated oxidation of cycloalkenes in the presence of air. The atmospheric implications of these results are discussed, along with a comparison with the reported structure activity relationships.
- Sharma,Pushpa,Dhanya,Naik,Bajai
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body text
p. 98 - 105
(2011/06/21)
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- Palladium-catalyzed asymmetric synthesis of allylic fluorides
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The enantioselective fluorination of readily available cyclic allylic chlorides with AgF has been accomplished using a Pd(0) catalyst and Trost bisphosphine ligand. The reactions proceed with unprecedented ease of operation for Pd-mediated nucleophilic fluorination, allowing access to highly enantioenriched cyclic allylic fluorides that bear diverse functional groups. Evidence that supports a mechanism in which C-F bond formation occurs by an SN2-type attack of fluoride on a Pd(II)-allyl intermediate is presented.
- Katcher, Matthew H.,Doyle, Abigail G.
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supporting information; experimental part
p. 17402 - 17404
(2011/02/23)
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- Rhodium-catalyzed activation of C(sp3)-X (X = Cl, Br) bond: An intermolecular halogen exchange case
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A RhCl(PPh3)3-catalyzed halogen-exchange reaction between allyl and alkyl halides with β-H atoms was observed. The possible mechanism of the reaction involves oxidative addition and reductive elimination of the C(sp3)-X bonds, which is not common in organometallic chemistry.
- Wang, Jianping,Tong, Xiaofeng,Xie, Xiaomin,Zhang, Zhaoguo
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supporting information; experimental part
p. 5370 - 5373
(2011/03/19)
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- Addition of bromotrichloromethane and tetrachloromethane to cis-cyclooctene, cyclohexene, and norbornadiene in the presence of palladium(II) complexes
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Addition of bromotrichloromethane and tetrachloromethane to alkenes in the presence of palladium(II) complexes begins with single-electron transfer from the palladium atom to polyhalomethane molecule, followed by fragmentation of the radical anion thus formed and generation of trichloromethyl radical. Halogen transfer to a carbon-centered radical arising from addition of trichloromethyl radical at the double bond occurs both from the polyhalomethane molecule and from halide palladium complex.
- Dneprovskii,Ermoshkin,Kasatochkin,Boyarskii
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p. 933 - 946
(2007/10/03)
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- Quaternary ammonium polychlorides as efficient reagents for chlorination of unsaturated compounds
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Chlorination of unsaturated compounds by benzyltributylammonium polychlorides results in higher yields of addition products compared to those obtained with molecular chlorine.
- Zelikman,Tyurin,Smirnov,Zyk
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p. 1541 - 1546
(2007/10/03)
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- The Reaction between Acyl Halides and Alcohols: Alkyl Halide vs. Ester Formation
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In the reaction between an acyl halide and an alcohol the thermodynamically favoured products are the free carboxylic acid and the alkyl halide.The initial reaction is, generally, the formation of an ester and HHal.When the alcohol is very prone to yield an alkyl cation upon protonation by HHal, formed H2O exhibited a superior reactivity and competed successfully with the alcohol for the acyl halide making, therefore, ester formation practically confined to a triggering role.But, in those cases where the cation is less easily formed, ester formation was favoured and, consequently, became the necessary elementary step towards alkyl halide formation.Tis final product, on the other hand, might be extremely slow to form in an SN2 reaction between the protonated ester function and the halide ion.In these instances, therefore, as well as in the cases when a basic solvent competes for the proton of HHal, the ester is the final product.A notable exception of the situation above outlined, is given by α-hydroxy-α-phenylbenzeneacetic acid (2y), which appears to undergo direct chlorine-hydroxyl interchange through a quaternary intermediate (E), in the end collapsing to α-chloro-α-phenyl-benzeneacetic acid (4y).Different systems were compared using CH2Cl2 as a solvent under strictly similar conditions.Some 28 different substrates were tested for reaction with AcCl (1a), whereas the action of eight acyl halides (a) against (RS)-α-methylbenzenemethanol (2n) and α-phenylbenzenemethanol (2p), as well as the effect of five different solvents on the reaction between two alcohols (2p and 2-methyl-2-propanol, 2c) with 1a, were observed.
- Strazzolini, Paolo,Giumanini, Angelo G.,Verardo, Giancarlo
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p. 217 - 254
(2007/10/02)
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- SYNTHESES DE CARBONATES ET CARBAMATES BENZYLIQUES ET ALLYLIQUES
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Different methods for the preparation of carbonates and carbamates derived from 1-phenylethyl, 2-cyclohexenyl and 1-methyl-2-propenyl are described.These conmpounds have been synthesized by the reactions of alcohols, phenols or amines with chloroformiates, imidazolocarbonates or corresponding mixed p-nitrophenylcarbonates. It is shown that these reactions can also be used for the introduction of 1-phenylethyloxycarbonyl - (I), 2-cyclohexenyloxycarbonyl - (II) and 1-methyl-2-propenyloxycarbonyl - (III) groups into alcohols, phenols and amines for the protection of hydroxyls and amino-groups.
- Kryczka, Boguslaw
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p. 147 - 158
(2007/10/02)
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- Reaction of alkylhypochlorites and xenon difluoride with cyclohexene
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Reactions of alkylhypochlorites and xenon difluoride with cyclohexene give primarily 1-chloro-2-fluorocyclohexanes via formation of a complex between xenon difluoride and the alkylhypochlorite.
- Shellhamer,Horney,Toth,Heasley
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p. 6903 - 6906
(2007/10/02)
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- Lewis acidic catalysts for olefin epoxidation by iodosylbenzene
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A ferric complex, (Et3HN) FeIII(bpb)Cl2, has been synthesized, and its structure has been determined by X-ray crystallography. This complex and its inflate derivative, (Et3HN)FeIII(bpb)(OTf)2, are found to catalyze the epoxidation of a variety of olefins by iodosylbenzene, OIPh. These reactions give little allylic oxidation of cyclohexene and stereochemical retention with cis-stilbene. Al(OTf)3, a nonredox metal salt, has also been found to catalyze the epoxidation of cyclohexene by iodosylbenzene, and the reactivity is quite similar to that of Fe(OTf)3, which, we studied previously. In addition to epoxides, other products were observed. For the reactions containing Fe(OTf)3, Al(OTf)3, or (Et3HN) FeIII(bpb)(OTf)2, cis-1,2-cyclohexanediol ditrifilate and 3-acetamidocyclohexene were found. The amide oxygen in 3-acetamidocyclohexene was derived from iodosylbenzene as verified by isotopic labeling using 18OIPh. For the reactions containing (Et3HN) FeIII(bpb)Cl2 FeCl3, or AlCl3, trans-1,2-dichlorocyclohexane and 3-chlorocyclohexene were observed. 1,4-Diiodobenzene was found in all of the reactions. The presence of these products suggests strongly that the mechanisms of these reactions are related to those occurring between soluble iodine(III)-containing compounds and olefins in the absence of any metal catalysts. A new mechanisms that accounts for all of the products is proposed which involves electrophilic attack on the olefin by the iodine(III) center in a metal-iodosylbenzene complex. The reactions of PhI(OAc)2 with norbornenecarboxylic acid or nortornene in different solvents were also investigated. The products isolated were shown to be 5-(acetyloxy)-3,3a,4,5,6,6a-hexahydro-[3β,3aα,5α,6β, 6aα]-3,6-methano-2H-cyclopenta [b] furan-2-one (1), 5-acetamido-3,3a,4,5,6,6a-hexahydro-[3β,3aα,5α,6β, 6aα]-3,6-methano-2H-cyclopenta [b] furan-2-one (2), and exo-2-acetoxy-syn-7-acetamidonorbornane (3). The structures of 1 and 3 were determined by X-ray crystallography. The formation of these products provides additional evidence for the electrophilic character of iodine(III) compounds.
- Yang, Yihui,Diederich, Fran?ois,Valentine, Joan Selverstone
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p. 7195 - 7205
(2007/10/02)
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- Reaction of Dilithiated Carboxylic Acids with Iodine: Evidence for the Formation of a Radical Anion Intermediate
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The mechanism for oxidative dimerization of carboxylic acid dianions involves single electron transfer to iodine, producing an organic anion radical.Rearrangement of this species was observed with suitable substrates at a rate competitive with intermolecular reactions.The radical anion can dimerize or react with iodine.The iodide thus generated can be isolated (reaction with excess of iodine) or can participate in a polar SN2-type reaction sequence leading to dimeric products (reaction with 1/2 equiv of iodine).The interference by free amines (liberated during the metalation with lithium amides) is rationalized by the formation of a charge-transfer complex with iodine which decomposes, liberating protons.
- Renaud, Philippe,Fox, Marye Anne
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p. 3745 - 3752
(2007/10/02)
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- HETEROGENEOUS ASYMMETRIC RING-OPENING REACTIONS OF PROCHIRAL EPOXIDES INCLUDED AS GUEST MOLECULES IN TRI-o-THYMOTIDE CLATHRATES.
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Enantiomorphous tri-o-thymotide clathrates of prochiral oxiranes were submitted to the action of gaseous hydrogen halides.Ring-opening reactions ensued that differ from those reported in homogeneous phase, showing a considerable modification of the chemical reactivity of the external reagent in the host lattice.Chirality transfer from the host receptors to the guest products was also observed, but with a poor efficiency.
- Gerdil, Raymond,Barchietto, Giacomo
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p. 4685 - 4688
(2007/10/02)
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- Oxygenated alkyl substituted bicyclo alkanes
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Anti-androgenic composition compound of the formula STR1 wherein Q is CO, CH(OR), CR(OH), or CR (OC)-lower alkyl);R is H, or C 1-2 -alkyl;X is hydroxyalkyl, methoxy-C 2-11 -alkyl, ethoxy-C 2-11 -alkyl or oxo-C 2-11 -alkyl, formyl-C 2-11 -alkyl, carboxy-C 2-11 -alkyl or (C 1-2 -alkyl) oxycarbonyl-C 2-11 -alkyl;c is 1 or 2;p or w are 0, 1 or 2 and the sum of p and w is 1 to 4;and a pharmaceutically acceptable salt thereof.
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- Anti-tumor halo bicyclo alkanones
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Potent tumor inhibitors are prepared which are compounds of the formula: STR1 wherein Q is CO, CH(OH) or C(OH)CH3, M1 is halogen, M2 is halogen or hydrogen, c is one or two p is 0 or 1, and one of X and X' is H and the other is hydroxy-C2-9 alkyl, methoxy-C2-9 -alkyl, ethoxy-C2-9 -alkyl, oxo-C2-9 -alkyl, formyl-C2-9 -alkyl, carboxy-C2-9 -alkyl or (C1-2 -alkyl)oxycarbonyl-C2-9 -alkyl.
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- BORON TRIFLUORIDE PROMOTED REACTIONS OF N-HALOELECTROPHILES WITH ALKENES
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N-Haloelectrophiles react with alkenes in the presence of boron trifluoride etherate to give halofluorides and N-halo adducts.
- Heasley, Gene E.,Janes, J. Mark,Stark, Stephen R.,Robinson, Brian L.,Heasley, Victor L.,Shellhamer, Dale F.
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p. 1811 - 1814
(2007/10/02)
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- HIGHLY ENANTIOSELECTIVE ISOMERIZATION OF PROCHIRAL ALLYLAMINES CATALYZED BY CHIRAL DIPHOSPHINE RHODIUM(I) COMPLEXES. PREPARATION OF OPTICALLY ACTIVE ENAMINES
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Rh(I) complexes of types ClO4 and n>ClO4 (diphosphine = cis-chelating tertiary diphosphine; diene = 1,5-cyclooctadiene or norbornadiene; S = solvent) were found to be effective catalists for allylic hydrogen migration of tertiary and secondary allylamines to give the corresponding (E)-enamines and imines, respectively.Studies on diphosphine ligands with respect to the catalytic activity and product selectivity led to the discovery of a fully aryl-substituted diphosphine, BINAP , which produces very active Rh(I) complex catalysts.With ClO4 (COD = 1,5-cyclooctadiene) or n>ClO4 as catalyst, (Z)-(diethylnerylamine, 1) or (E)-N,N-diethyl-3,7-dimethyl-2,6-octadienylamine (diethylgeranylamine, 2) was isomerized into the racemic (E)-enamine (E)-N,N-diethyl-3,7dimethyl-1,6-octadienylamine (citronellenamine, 3) with a chemical selectivity of over 95percent, the 6-double bond being retained intact.A variety of substituted allylamines serves as the substrate, e.g., (E)-N,N-dimethyl-2-butenylamine, N,N-dimethyl-2-methyl-2-propenylamine, N,N-dimethyl-3-methyl-2-butenylamine, N,N-dimethyl-3-phenyl-2-butenylamine.Asymmetric isomerization of prochiral allylamines producing optically active enamines or imines can be effected with cationic Rh(I) complexes of various chiral diphosphine ligands such as (2R,3R)-DIOP and others.The ligand that gives the highest optical yield was (+)- or (-)-BINAP.Virtually perfect enantioselectivity (95-99percent ee) was achieved with + for the isomerization of 1 or 2 into the optically active (E)-enamine (3).A clear stereochemical correlation was established between the olefin geometry (E or Z) of substrates, the configuration of the chiral diphosphines (R or S), and the chiral carbon configuration of the product enamines (R or S).The present catalytic system thus provides a convenient and practical access to optically active aldehydes.For example, optically pure natural citronellal can be produced either from nerylamine with the Rh(I)-(+)-BINAP catalyst or from geranylamine with the Rh(I)-(-)-BINAP complex catalyst.
- Tani, Kazuhide,Yamagata, Tsuneaki,Akutagawa, Susumu,Kumobayashi, Hidenori,Taketomi, Takanao,et al.
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p. 5208 - 5217
(2007/10/02)
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- Alkylmetal Asymmetric Reduction. 14. Enantioselective Reduction of Ketones by Chiral (2-Methylbutyl)aluminum Derivatives
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The reaction of trisaluminum with some α-alkynyl ketones has been studied: the organoaluminum derivative rapidly reduces the ketones to afford optically active α-alkynyl carbinols, which can be recovered after hydrolytic workup.The sterochemical results obtained are discussed on the basis of previous reports on enantioselective reductions of ketones by an alkylaluminum dichloride derived from β-pinene.In this context, an investigation on the reaction between a series of ketones and β-branched alkylaluminum chlorides is also reported.
- Giacomelli, Giampaolo,Lardicci, Luciano,Palla, Fabio,Caporusso, Anna Maria
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p. 1725 - 1728
(2007/10/02)
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- MECHANISMS OF EPOXIDATIONS AND CHLORINATIONS OF HYDROCARBONS BY INORGANIC HYPOCHLORITE IN THE PRESENCE OF A PHASE-TRANSFER CATALYST.
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Inorganic hypochlorite in the presence of a quarternary ammonium salt (phase-transfer catalyst) not only epoxidizes several arenes to arene oxides in high yields but also converts toluene to alpha -chlorotoluene, anisole to ring chlorinated anisoles, and alkenes to a complex mixture of chlorinated and oxidized products, including the epoxide. More detailed studies with this system indicate the following: (1) the high-yield conversion of toluenes to benzyl chlorides proceeds with a deuterium isotope effect of 3. 6 and a rho ** plus value of minus 1. 7: (2) p-chloroanisole is the major product from anisole and is formed in a 22-fold greater quantity than o-chloroanisole; (3) the epoxidation of cis- and trans-alkenes is stereoselective but not completely stereospecific; (4) the chlorination of saturated hydrocarbons occurs with a selectivity that is experimentally identical with that of chlorine monoxide.
- Fonouni,Krishnan,Kuhn,Hamilton
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p. 7672 - 7676
(2007/10/02)
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- Hydrocarbon Functionalization by the (Iodosylbenzene)manganese(IV) Porphyrin Complexes from the (Tetraphenylporphinato)manganese(III)-Iodosylbenzene Catalytic Hydrocarbon Oxidation System. Mechanism and Reaction Chemistry
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The two types of complexes isolated from the reaction of (tetraphenylporphinato)manganese(III) derivatives, XMnIIITPP, with iodosylbenzene - IVTPP(OIPh)>2O, 1, X = Cl- or Br-, and IVTPP>2O, 2, X = N3- - are capable of oxidizing alkane substrates in good yields at room temperature.Several lines of evidence establish the intermediacy of free alkyl radicals in the reactions of 1 and 2 with alkanes.Oxygen exchange with water in both the iodosyl (Mn-O-I) and μ-oxo (Mn-O-Mn) moieties of 1 suggests the formation of oxo manganese porphyrin complexes from these moieties.Hydrogen abstraction from the alkane substrate by an oxo manganese porphyrin intermediate is postulated to be mechanism for reaction of 1 and 2 with alkanes.Observation of a monomeric manganese(IV) porphyrin intermediate by EPR spectroscopy during the reactions of 1 with alkanes is consistent with the formation of a hydroxymanganese(IV) porphyrin complex resulting from substrate hydrogen abstraction by an oxo intermediate.The formation of RX product from oxidation of RH by 1 has been determined to result from ligand-transfer oxidation of free alkyl radicals by the porphyrin complexes in solution.Through competition reactions and time-dependent product formation studies, ligand-transfer oxidation by XMnIIITPP was found to be the major pathway for RX production.Observation of MnIITPP by EPR spectroscopy during the reactions of 1 with alkanes supports this conclusion.Formation of ROH product may result from ligand-transfer oxidation of free radicals or from the collapse of an intermediate caged radical pair.The mechanism of ROH product formation in the caged radical pair is postulated to be an outer-sphere electron-transfer process due to the expected slow rate of inner-sphere ligand transfer for the high-spin d3 hydroxymanganese(IV) porphyrin complex.Thus the ability of the substrate radical to undergo electron-transfer oxidation determines the ratio of radicals that undergo cage escape to give free radicals to radicals that undergo oxidation and subsequent formation of alcohol product in the caged species.Studies with tertiary substrates support these conclusions.
- Smegal, John A.,Hill, Craig L.
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p. 3515 - 3521
(2007/10/02)
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- Reactions of (Organostannyl)- and (Organogermyl)lithium Reagents with Some (Allylic) Cyclohex-2-enyl Chlorides
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The stereo- and regiochemistries of the reactions between (trimethylgermyl)lithium, (triphenylstannyl)lithium, and (trimethylstannyl)lithium and cis- and trans-5-methyl-2-cyclohexenyl chlorides, 3,5-dimethyl-2-cyclohexenyl chlorides, and some deuterated derivatives have been investigated utilizing 1H, 2H, 13C, and 119Sn nuclear magnetic resonance spectroscopy.The major substitution pathway (forming the allylic organometallic) involves configurational inversion at carbon and is accompanied by an insignificant level of 2H relocation between the allylic positions.The SN2 mechanism is strongly implicated.Serious side reactions accompany the reactions of (trimethylgermyl)lithium generated in hexamethylphosphoric triamide (HMPA), and significant amounts of digermanes and cyclohexenyldimethylamines form.The latter almost certainly result from chloride displacement by dimethylamide ((CH3)2N:-, formed by alkali metal cleavage of HMPA), such displacement proceeding regio- and stereospecifically in accord with the SN2 pathway.Pentamethyl(cyclohex-2-enyl)digermanes which are formed stereospecifically, are considered to result from chloride displacement by (pentamethyldigermyl)lithium, formed by dimethylgermylene insertion into (trimethylgermyl)lithium itself.Certain redistribution reactions of the pentamethyl(cyclohex-2-enyl)digermanes have been observed.
- Wickham, Geoffrey,Young, David,Kitching, William
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p. 4884 - 4895
(2007/10/02)
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- The photochemical addition of N-haloamides to olefins: the influence of various factors on the competition between 1,2-addition and hydrogen abstraction
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In the photodecomposition of N-haloamides (ZCONRX) in the presence of olefins, the 1,2-addition chain competes with the hydrogen abstraction chain(s) leading to the parent amide (the quantum yields for these processes are greater than unity).The following factors were shown to have an influence on this competition as measured by the yield of 1,2-addition and the yield of parent amide in methylene chloride solutions: (i) the N-halogen (higher yields of addition with X=Cl than with X=Br); (ii) the electronegativity of Z (increase of the yield of addition as the electronegativity of Z increases); (iii) the temperature (higher yields of addition at lower temperatures, and at -70 degC, better yields of addition (>90percent, R=H) for X=Br than for X=Cl); and (iv) the size of R (dramatic decrease of the yield of 1,2-addition in going from R=H to R=CH3).Surprisingly, the presence of a scavenger for HX had no influence on the yield of 1,2-addition.Both the size and electronegativity of Z had an effect on the stereochemistry of 1,2-addition to cyclohexene.High yields of addition to a variety of olefins were obtained with N-chloroamides such as ClCH2CONHCl, C2H5OCONHCl, CF3CONHCl.Their addition to enol ethers at -70 degC led to the synthesis of α-amido acetals or ketals (aldehydes or ketones) and to an α-amido glycoside in good yields.
- Lessard, Jean,Mondon, Martine,Touchard, Daniel
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p. 431 - 450
(2007/10/02)
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- THE REACTION OF HYPOCHLOROUS ACID WITH OLEFINS. A CONVENIENT SYNTHESYS OF ALLYLIC CHLORIDES
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The reaction of HOCl with more highly substituted olefins in methylene chloride affords allylic chlorides in 60-80percent isolated yields.The utility of the reaction is illustrated with the synthesis of Rose oxide and α-monoterpenes.
- Hegde, Shridhar G.,Vogel, Martin K.,Saddler, John,Hrinyo, Tanya,Rockwell, Ned,et al.
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p. 441 - 444
(2007/10/02)
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