- Regioselective Synthesis of α-Functional Stilbenes via Precise Control of Rapid cis- trans Isomerization in Flow
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The rapid cis-trans isomerization of α-anionic stilbene was regioselectively controlled by using flow microreactors, and its reaction with various electrophiles was conducted. The reaction time was precisely controlled within milliseconds to seconds at -50 °C to selectively give the cis- or trans-isomer in high yields. This synthetic method in flow was well-applied to synthesize precursors of commercial drug compound, (E)- and (Z)-tamoxifen with high regioselectivity and productivity.
- Lee, Hyune-Jea,Yonekura, Yuya,Kim, Nayoung,Yoshida, Jun-Ichi,Kim, Heejin
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p. 2904 - 2910
(2021/05/05)
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- Iridium-Catalyzed Hydrochlorination and Hydrobromination of Alkynes by Shuttle Catalysis
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Described herein are two different methods for the synthesis of vinyl halides by a shuttle catalysis based iridium-catalyzed transfer hydrohalogenation of unactivated alkynes. The use of 4-chlorobutan-2-one or tert-butyl halide as donors of hydrogen halides allows this transformation in the absence of corrosive reagents, such as hydrogen halides or acid chlorides, thus largely improving the functional-group tolerance and safety profile of these reactions compared to the state-of-the-art. This method has granted access to alkenyl halide compounds containing acid-sensitive groups, such as tertiary alcohols, silyl ethers, and acetals. The synthetic value of those methodologies has been demonstrated by gram-scale synthesis where low catalyst loading was achieved.
- Yu, Peng,Bismuto, Alessandro,Morandi, Bill
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supporting information
p. 2904 - 2910
(2020/01/25)
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- Iodine(III)-Mediated Oxidative Hydrolysis of Haloalkenes: Access to α-Halo Ketones by a Release-and-Catch Mechanism
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An unprecedented iodine(III)-mediated oxidative transposition of vinyl halides has been accomplished. The products obtained, α-halo ketones, are useful and polyvalent synthetic precursors. There are only a handful of reported examples of the direct conversion of vinyl halides to their corresponding α-halo carbonyl compounds. Insights into the mechanism and demonstration that this synthetic transformation can be done under enantioselective conditions are reported.
- Jobin-Des Lauriers, Antoine,Legault, Claude Y.
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supporting information
p. 108 - 111
(2016/01/15)
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- Selective Ruthenium-Catalyzed Hydrochlorination of Alkynes: One-Step Synthesis of Vinylchlorides
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An unprecedented ruthenium-catalyzed direct and selective alkyne hydrochlorination is reported and leads to vinylchlorides in excellent yields with atom economy. The reaction proceeds at room temperature from terminal alkynes and provides a variety of chloroalkenes. Only the regioisomer resulting from the formal Markovnikov addition is selectively formed. Mechanistic studies show the stereoselective syn addition of HCl to alkynes at room temperature and suggest a chloro hydrido RuIV species as a key intermediate of the reaction.
- Dérien, Sylvie,Klein, Hubert,Bruneau, Christian
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supporting information
p. 12112 - 12115
(2015/10/12)
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- Iridium-catalyzed addition of aroyl chlorides and aliphatic acid chlorides to terminal alkynes
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Iridium complexes show high catalytic activity in intermolecular additions of acid chlorides to terminal alkynes to afford valuable (Z)-β-chloro- α,β-unsaturated ketones. Ligands in the catalytic system play a crucial role in this reaction. An N-heterocyclic carbene (NHC) is an efficient ligand for the addition of aroyl chlorides, while dicyclohexyl(2-methylphenyl) phosphine (PCy2(o-Tol)) is indispensable for the reaction of aliphatic acid chlorides. The addition reactions proceed regio- and stereoselectively with suppression of decarbonylation and β-hydrogen elimination, which have been two major intrinsic problems in transition-metal-catalyzed reactions. Stoichiometric reactions of active iridium catalysts with aroyl chlorides and aliphatic acid chlorides are carried out to gain insights into the reaction mechanisms.
- Iwai, Tomohiro,Fujihara, Tetsuaki,Terao, Jun,Tsuji, Yasushi
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supporting information; experimental part
p. 1268 - 1274
(2012/03/12)
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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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scheme or table
p. 1832 - 1848
(2011/04/15)
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- Mesoionic carbenes: Reactions of 1, 3-diphenyltetrazol-5-ylidene with electron-deficient alkenes, and synthesis and catalytic activities of the (tetrazol-5-ylidene)rhodium(I) complexes
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The reactions of 1, 3-diphenyltetrazol-5-ylidene, a rare example of mesoionic carbenes, with electron- deficient unsaturated compounds were studied. The carbene reacted with dimethyl 1, 2, 4, 5-tetrazine-3, 6-dicarboxylate to give a 5-tetrazoliomethylide, together with hydrazine derivatives. The reaction with tetracyanoethylene gave another methylide in low yield. On the contrary, the reactions with weaker electrophiles, such as 3, 6-diphenyl-1, 2, 4, 5-tetrazine, fumalonitrile, N-phenylmaleimide, and dimethyl acetylenedicarboxylate, did not give any coupling products, but gave phenylated products and/or Michael addition products via the degradation of the 1, 3-diphenyltetrazole ring. Novel mesoionic mono- and bis(carbene)-rhodium(I) complexes were synthesized and the structures were characterized by X-ray crystallography. Their catalytic activities for the decarbonylative addition reaction of benzoyl chloride to ethynylbenzene were investigated.
- Araki, Shuki,Yokoi, Keisaku,Sato, Ryosuke,Hirashita, Tsunehisa,Setsune, Jun-Ichiro
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scheme or table
p. 164 - 171
(2009/07/17)
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- Palladium(0)-catalyzed cross-coupling of potassium (z)-2-chloroalk-1-enyl trifluoroborates: A chemo- and stereoselective access to (z)-chloroolefins and trisubstituted alkenes
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We describe the preparation of a series of new potassium trifluoroborates 1 and the study of their behaviour in a Pd0-catalyzed cross-coupling reaction. We found that compounds 1 are endowed with original properties as they behave as nucleophil
- Guinchard, Xavier,Bugaut, Xavier,Cook, Cyril,Roulland, Emmanuel
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supporting information; experimental part
p. 5793 - 5798
(2010/01/15)
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- Iridium-catalyzed addition of acid chlorides to terminal alkynes
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(Chemical Equation Presented) An iridium N-heterocyclic carbene (NHC) complex, IrCl(cod)(IPr), successfully catalyzed an addition of common aromatic acid chlorides to terminal alkynes to afford (Z)-β-chloro-α,β- unsaturated ketones regio- and stereoselectively. When the NHC ligand (IPr) was changed to a phosphine (RuPhos), the addition occurred with decarbonylation to give the corresponding (Z)-vinyl chlorides. Furthermore, the former reaction using IrCl(cod)(IPr) can be applied to the catalytic synthesis of 2,5-disubstituted furans.
- Iwai, Tomohiro,Fujihara, Tetsuaki,Terao, Jun,Tsuji, Yasushi
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supporting information; experimental part
p. 6668 - 6669
(2009/10/30)
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- First catalytic and green synthesis of aryl-(Z)-vinyl chlorides and its plausible addition-elimination mechanism
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(Chemical Equation Presented) Via a catalytic cycle in the presence of scandium triflate (2 mol %)/DMF (1 mol %)/benzoyl chloride (5 mol %), aromatic ketones were treated with bis(trichloromethyl) carbonate (BTC) to afford aryl-(Z)-vinyl chlorides. All metal triflates tested in the reaction showed highly catalytic activity. A plausible addition-elimination mechanism was proposed. The present work describes the first catalytic and green route to the synthesis of aryl-(Z)-vinyl chlorides.
- Su, Weike,Jin, Can
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p. 993 - 996
(2007/10/03)
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- Stereoselective CrCl2-mediated condensation of aldehydes with functionalized 1,1,1-trichlorides: Synthesis of trisubstituted (Z)-chloroolefins
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The CrCl2-mediated condensation of aldehydes 1 with a variety of functionalized 1,1,1-trichlorides 2 affords trisubstituted chloroolefins 4 in excellent yields and generally high Z-stereoselectivity. The intermediate dichlorohydrin adducts 3 can be isolated in good yields under conditions of limited reagent and reduced temperature.
- Falck,Bandyopadhyay, Anish,Barma,Shin, Dong-Soo,Kundu, Abhijit,Krishna Kishore
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p. 3039 - 3042
(2007/10/03)
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- Synthesis of dihalohydrins and tri- and tetra-substituted olefins
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A novel synthesis reaction for highly stereospecific tri- and tetra-substituted olefins is described. A single stereoisomer of stable α-halo-α,β-ester is produced in high yield by the reaction of aldehyde or ketone with a trihalogenated compound such as t
- -
-
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- Pd-catalyzed selective tandem arylation-alkylation of 1,1-dihalo-1-alkenes with aryl- and alkylzinc derivatives to produce α-alkyl-substituted styrene derivatives
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Trans -selective monoarylation of 1,1-dibromo- and 1,1-dichloro-1-alkenes (1) can be achieved in >80% yields and in ≥98-99% stereoselectivity with arylzinc bromides in the presence of a catalytic amount of Cl2Pd(DPEphos) or Cl2Pd(dppb), the former permitting cleaner and higher yielding reactions. Although THF is a generally satisfactory solvent, ether and toluene are superior to THF in some cases. The second substitution of (Z)-α-bromostyrenes (3) with alkylzincs in the presence of 2 mol% of Pd(t Bu3P)2 proceeds to give the corresponding 2 in >90% yields and in ≥98-99% stereoselectivity. Although somewhat less satisfactory, the use of Cl2Pd(DPEphos) permits a one-pot tandem arylation-alkylation.
- Shi, Ji-cheng,Negishi, Ei-ichi
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p. 518 - 524
(2007/10/03)
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- Rhodium-catalyzed reaction of aroyl chlorides with alkynes or alkenes in the presence of disilanes
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Internal alkynes effectively undergo aroylarylation, that is 1,2-addition of aroyl and aryl groups, on treatment with aroyl chlorides in the presence of a catalytic amount of [RhCl(cod)]2 and PPh3 using hexamethyldisilane as reducing agent to produce the corresponding 1,3-diaryl-2-propen-1-one derivatives in good yields. The reaction can also proceed using relatively reactive alkenes such as norbornenes in place of the alkynes. Similar treatment of a terminal alkyne, phenylacetylene, with aroyl chlorides brings about aroylsilylation to give 1-aryl-2-phenyl-3-trimethylsilyl-2-propene-1-ones.
- Kokubo, Ken,Matsumasa, Kenji,Miura, Masahiro,Nomura, Masakatsu
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p. 217 - 222
(2007/10/03)
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- Rhodium-catalyzed reaction of aroyl chlorides with alkynes
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Aroyl chlorides react with terminal alkynes accompanied by decarbonylation in the presence of a catalytic amount of [RhCl(cod)]2 and PPh3 to give the corresponding vinyl chloride derivatives regioand stereoselectively in good yields.
- Kokubo, Ken,Matsumasa, Kenji,Miura, Masahiro,Nomura, Masakatsu
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p. 6941 - 6946
(2007/10/03)
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- Surface-Mediated Reactions. 4. Hydrohalogenation of Alkynes
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The use of appropriately prepared silica gel and alumina has been found to mediate the addition of hydrogen halides to alkynes.The technique has been rendered even more convenient by the use of various organic and inorganic acid halides that react in the presence of silica gel or alumina to generate hydrogen halides in situ.Treatment in this fashion of 1-propynylbenzene (1), which underwent no reaction in CH2Cl2 solution saturated with HCl, readily afforded the syn addition product, alkenyl chloride (E)-4a.On extended treatment (E)-4a underwent subsequent iaomerization to the thermodynamically more stable Z isomer.Thus either isomer of 4a could be obtained in good yield depending on the reaction conditions.In a similar way bromides (E)- and (Z)-4b were obtained without competing formation of the radical products (E)- and (Z)-5, which occurred in solution.In contrast with solution-phase hydroiodination of alkyne 1, which slowly afforded iodide (E)-4c, surface-mediated addition readily afforded (E)-4c, followed by isomerization to the Z isomer.E ->/- Z equilibration of the alkenyl halides 4 was shown to involve, at last in part, addition-elimination via the gem-dihalides 13.Analogous behavior was exhibited by the phenylalkynes 2 and 3 on surface-mediated hydrohalogenation.Surface-mediated addition of HBr and HI to the internal alkylalkyne 14 afforded principally the anti addition products (Z)-15b,c.Treatment of the terminal alkynes 17 and 22 with (COBr)2 over alumina gave the dibromides 20 and 24/25, respectively, whereas use of acetyl bromide as the HBr precursor afforded the alkenyl bromides 18b and 23.
- Kropp, Paul J.,Crawford, Scott D.
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p. 3102 - 3112
(2007/10/02)
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- The reaction of benzotrihalides and benzal halides with magnesium. Synthetic and mechanistic studies
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The benzotrihalides (PhCX3) where X = Cl, Br, and F were allowed to react with magnesium in THF at room temperature.When the halide was chloride or bromide, the trihalide gave diphenylacetylene in high yield in addition to several minor products which were identified.No reaction was observed when the halide was fluoride.When the corresponding dichloride was allowed to react with magnesium in THF, stilbene was formed as the major product.The possible mechanisms for these reactions are discussed.
- Ashby, E. C.,Al-Fekri, Dheya M.
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p. 275 - 292
(2007/10/02)
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- Phenylselenium Trichloride in Organic Synthesis. Reaction with Unsaturated Compounds. Preparation of Vinylic Chlorides via Selenoxide Elimination
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Phenylselenium trichloride, PhSeCl3, was reacted with a number olefinic compounds to produce (β-chloroalkyl)phenylselenium dichlorides.The addition was anti stereospecific and irreversible.The presence of an oxygen substituent (acyloxy or aryloxy group) in the allylic position of the olefin directed the attack of PhSeCl3 to occur regiospecifically anti-Markovnikov to give a (β-acyloxy/aryloxy-β'-chloroalkyl)phenylselenium dichloride.When the (β-chloroalkyl)phenylselenium dichlorides were treated in methylene chloride with aqueous sodium hydrogen carbonate, the selenium dichloride moiety was readily hydrolyzed to a selenoxide, which underwent the usual selenoxide elimination reaction to produce an allylic or a vinylic chloride.Symmetrical olefins containing no allylic hydrogens were converted to vinylic chlorides with retention of olefin geometry.Olefins containing a directing oxygen substituent in the allylic position afforded vinylic chlorides where the vinylic halogen atom was oriented 1,3 to the oxygen substituent (E/Z mixture).Other olefins afforded mixtures of allylic and vinylic halides in varying proportions.The reaction of phenyselenium tribromide, PhSeBr3, with some olefinic compounds was also investigated.This material showed the same stereo- and regiochemical behavior as PhSeCl3 in its addition reactions.However, the adducts were not useful for the preparation of vinylic or allylic bromides by using the hydrolytic selenoxide elimination reaction.
- Engman, Lars
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p. 4086 - 4094
(2007/10/02)
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- A NEW REDUCTION SYSTEM: COMBINATION OF SODIUM SULFIDE (SODIUM HYDROSULFIDE) WITH PHASE TRANSFER AGENT IN A TWO PHASE MIXTURE. REDUCTIVE DEBROMINATION OF vic-DIBROMIDES TO OLEFINS
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A wide variety of vic-dibromides are debrominated to the corresponding olefins in good to excellent yields by aqueous sodium sulfide or sodium hydrosulfide using trioctylmethylammonium chloride as the phase transfer agent in a two-phase mixture.
- Nakayama, Juzo,Machida, Haruki,Hoshino, Masamatsu
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p. 3001 - 3004
(2007/10/02)
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- Three-membered Ring Heterocycles, 14. α-Halogenation of Tertiary Phosphane Oxides
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The symmetrically substituted tertiary phosphane oxides 5 were obtained from phosphorus halides 4 and 6 using organometallic reagents.Dibenzylphenylphosphane oxide (5c) reacted with bromine at 150 deg C to give all three possible diastereomeric α,α'-dibromophosphane oxides. e.g. (R,R/S,S)-2c, (r)-2c, and (s)-2c, and one α-bromophosphane oxide 8.The phosphane oxides 5a, b, d were lithiated once or twice in the α-positions by means of butyllithium.The α,α'-dilithiophoasphane oxides -5 reacted with tetrachloromethane below -80 deg C to yield the α-chlorophosphane oxides 1c - e whose diastereomeric ratios were controlled kinetically.The thermodynamically controlled ratios were adjusted with bases.While the α-lithiated dineopentyl phosphane oxides -5a and -5d also afforded the α-chlorophosphane oxides 1c and 1d, respectively, with an excess of tetrachloromethane, the α,α-dichlorophosphane oxide 9 was formed from the α-lithiobenzylphosphane oxide 5b.This difference is attributed to the acidity of the α-protons and steric factors.The configurations and preferred conformations of the α,α'-dibromophosphane oxides 2c and the α-chlorophosphane oxides 1c - e were determined on the basis of the 1H-31P coupling of the methine protons.
- Heuschmann, Manfred,Quast, Helmut
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p. 3384 - 3401
(2007/10/02)
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