- Synthesis of acetylenes via dehydrobromination using solid anhydrous potassium phosphate as the base under phase-transfer conditions
-
Phase-transfer catalyzed preparation of acetylenes from the corresponding vicinal dibromo compounds via double dehydrobromination using the mild solid base, anhydrous potassium phosphate, under very mild conditions is reported.
- Shenawi-Khalil, Sanaa,Sonavane, Sachin U.,Sasson, Yoel
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p. 2295 - 2297
(2012/07/27)
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- Weakly nucleophilic conjugate bases of superacids as powerful nucleophiles in vinylic bimolecular nucleophilic substitutions of simple β- alkylvinyl(aryl)-λ3-bromanes
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We report herein, for the first time, the stereoselective synthesis of simple (E)-β-alkylvinyl(aryl)-λ3-bromanes via a boron-λ3-bromane exchange reaction and their unique bimolecular nucleophilic substitutions at the vinylic ipso carbon atom under mild conditions. Interestingly, even weakly nucleophilic anions such as conjugate bases of superacids (HBF4, TfOH, Tf2CH 2, Tf3CH, Tf2NH, etc.) function as nucleophiles toward the vinyl-λ3-bromanes. For instance, the vinylic SN2 reaction of (E)-vinyl-λ3-bromanes with potassium bis(triflyl)methanide stereoselectively produced (Z)-vinyloxy oxosulfonium ylides with exclusive inversion of configuration via oxygen attack, while that with potassium bis(triflyl)imide afforded predominantly (Z)-vinyloxysulfoximines. In marked contrast, (E)-β-alkylvinyl- λ3-iodanes do not undergo the vinylic SN2 reaction with these conjugate bases of superacids. The differences between the nucleofugalities of aryl-λ3-iodanyl and aryl- λ3-bromanyl groups (the latter being greater) probably play a pivotal role in these unique reactions.
- Ochiai, Masahito,Okubo, Takuji,Miyamoto, Kazunori
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p. 3342 - 3344
(2011/05/04)
-
- Cross-coupling of nonactivated alkyl halides with alkynyl grignard reagents: A nickel pincer complex as the catalyst
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In a pinch: The nickel pincer complex 1 catalyzes the cross-coupling of the title compounds with remarkable substrate scope and functional group tolerance. A nickel/alkynyl species was isolated and shown to be catalytically competent. THF=tetrahydrofuran, O-TMEDA=bis[2-(N,N-dimethylaminoethyl)] ether. Copyright
- Vechorkin, Oleg,Godinat, Aurélien,Scopelliti, Rosario,Hu, Xile
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supporting information; experimental part
p. 11777 - 11781
(2012/01/19)
-
- Formation of conjugated polynaphthalene via Bergman cyclization
-
A series of enediyne containing chiral phthalimides were synthesized through Sonogashira coupling reactions. These enediynes were then subjected to thermal Bergman cyclization under vacuum. Polynaphthalenes with pendant chiral groups were obtained and characterized using GPC, IR spectroscopy, NMR spectroscopy, UV-Vis spectroscopy, and photoluminescence analysis. Under properly optimized conditions, the chirality of chiral directing group was maintained according to CD spectra of final products. After removal of chiral directing groups, weak CD signals representative of main chain chirality were visible. Further modification of the structure of the enediyne compounds will facilitate the synthesis of chiral polynaphthalene through this rather simple way. Extension of the Bergman cyclization to polymer chemistry is promising in the construction of novel polymers with rigid polyarene back-bones.
- Miao, Changcheng,Zhi, Jian,Sun, Shiyuan,Yang, Xi,Hu, Aiguo
-
experimental part
p. 2187 - 2193
(2011/04/15)
-
- Nucleophilic vinylic substitutions of (Z)-(2-aroyloxyvinyl)phenyl- λ3-iodanes with tetrabutylammonium halides: Vinylic S N2 reactions and ligand coupling on iodine(III)
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Treatment of (Z)-(β-benzoyloxyvinyl)phenyl-λ3- iodanes, readily prepared from ethynyl(phenyl)(tetrafluoroborato)- λ3-iodane via stereoselective Michael-type addition of benzoic acids in methanol in the presence of sodium benzoates, with tetrabutylammonium halides in THF at 65°C results in a vinylic SN2 reaction to give the inverted (E)-β-benzoyloxyvinyl halides in high yields.
- Ochiai, Masahito,Nishi, Yoshio,Hirobe, Masaya
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p. 1863 - 1866
(2007/10/03)
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- Claisen rearrangements based on vinyl fluorides
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2-Fluoroalk-1-en-3-ols (4), available from terminal alkenes (1) by bromofluorination, subsequent dehydrobromination of the 1-bromo-2-fluoroalkanes (2) to form 2-fluoroalkenes (3) and selenium dioxide mediated allylic oxidation with tert-butylhydroperoxide, undergo Johnson-Claisen rearrangement on treatment with trimethyl orthoacetate to give methyl 4-fluoroalk-4-enoates (7) in high yields. In contrast Ireland-Claisen rearrangement of 3-acetoxy-2-fluorodec-1-ene (9b) with triethylamine and TMSOTf in ether failed. Instead of the expected formation of a carboxylic acid, selective C-silylation of the α-position to the carboxyl group to form 14 occurred. However, Ireland-Claisen rearrangement was successful with corresponding chloroacetates 10 and propionates 11 of four 2-fluoroalk-1-en-3-ols (4) to give 2-chloro-4-fluoroalk- 4-enecarboxylic acids (15) or its 2-methyl derivatives 16, respectively, in moderate yields. These [3,3]-sigmatropic rearrangements are diastereoselective giving trans-configured double bonds, exclusively. Corresponding esters derived from (Z)-2-fluorocyclododec-2-enol (22), did rearrange to yield mixtures of diastereomers much less selectively. Also 2-fluorodec-2-enol (6), which was prepared by rearrangement of 2-fluoro-2-octyloxirane (5) with TMSOTf and triethylamine, was successfully applied as a starting material for [3,3]-sigmatropic rearrangements. The corresponding 3-(1-fluoroethenyl)alkanoic acid derivatives 17 and 18 were formed in moderate yield. 2-Fluoroalk-1-en-3-ol esters prepared in two steps from 2-fluoroalk-1-enes undergo Claisen rearrangements to form 2-substistuted 4-fluoroalk-4-enecarboxylic acids.
- Tranel, Frank,Haufe, Günter
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p. 1593 - 1608
(2007/10/03)
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- Borane-induced radical reduction of 1-alkenyl- and 1-alkynyl-λ3-iodanes with tetrahydrofuran
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Exposure of 1-alkenyl(phenyl)- and 1-alkynyl(phenyl)-λ3-iodanes to THF at room temperature in the presence of a catalytic amount of trialkylborane results in smooth reduction to give 1-iodo-1-alkenes and 1-iodo-1-alkynes as major products, respectively. The key step in the reductions probably involves a single-electron transfer from α-tetrahydrofuryl radical to the λ3-iodanes, which generates the labile [9-I-2] iodanyl radicals.
- Ochiai, Masahito,Tsuchimoto, Yoshimi,Hayashi, Takanori
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p. 5381 - 5384
(2007/10/03)
-
- Process for the preparation of cyclopropylacetylene
-
The present invention relates generally to novel methods for the preparation of cyclopropylacetylene which is an essential reagent in the asymmetric synthesis of (S)-6-chloro-4-cyclopropylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one; a useful human immunodeficiency virus (HIV) reverse transcriptase inhibitor with superior anti-retroviral activity. In the process, for example, cyclopropane carboxaldehyde is alkylated to form 1,1,1-trichloro-2-cyclopropyl-ethanol; which in turn undergoes elimination to form 1,1-dichloro-2-cyclopropyl-ethene; which in turn undergoes elimination to form cyclopropyl acetylene.
- -
-
Page column 14, 17-18
(2008/06/13)
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- Solvolysis of 1-decenyl(phenyl)iodonium tetrafluoroborate: Mechanisms of nucleophilic substitution and elimination
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Solvolysis of (E)-1-decenyl(phenyl)iodonium tetrafluoroborate 1 was carried out in some alcohols, acetic acid, and mixed aqueous alcoholic solvents at 50-60°C and the effects of added carboxylates and other salts were also examined in methanol. Reaction products include enol derivatives (substitution) and 1-decyne (elimination) as well as iodobenzene. Rates for the solvolysis increase with increasing nucleophilicity of the solvent but have no correlation with the solvent ionizing power. The substitution occurs mostly via inversion of configuration, and is concluded to follow the in-plane SN2 mechanism with a minor concomitant out-of-plane SN2 pathway. The reactions with the deuterated substrates show that stronger bases of pKa of the conjugate acid > 3 induce exclusively α-elimination of 1 in methanol. However, both α- and β-elimination occur in neutral methanol in a ratio of about 3/1 besides the substitution. Mechanisms for these reactions are proposed.
- Okuyama, Tadashi,Imamura, Shohei,Ishida, Yoshimi
-
p. 543 - 548
(2007/10/03)
-
- Process for the preparation of cyclopropylacetylene
-
The present invention relates generally to novel methods for the synthesis of cyclopropylacetylene which is an essential reagent in the asymmetric synthesis of (S)-6-chloro-4-cyclopropylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one; a useful human immunodeficiency virus (HIV) reverse transcriptase inhibitor. In the process, for example, cyclopropane carboxaldehyde is alkylated to form 1,1,1-trichloro-2-cyclopropyl-ethanol; which in turn is hydroxy protected to form 1,1,1-trichloro-2-cyclopropylethyltosylate; which in turn undergoes elimination to form cyclopropyl acetylene. This improvement provides for high conversion of inexpensive, readily available starting materials into cyclopropylacetylene, high overall yields and can be conducted on an industrial scale.
- -
-
-
- Stereoselective synthesis of (Z)-enethiols and their derivatives: Vinylic SN2 reaction of (E)-alkenyl(phenyl)-λ3-iodanes with thioamides
-
(Equation presented) Exposure of (E)-β-alkylvinyl(phenyl)-λ3-iodanes to thioamides in dichloromethane at room temperature was found to result in a bimolecular nucleophilic substitution (SN2) at the vinylic carbon atom to give inverted (Z)-enethiols and/or (Z)-S-vinylthioimidonium salts. Vinylic SN2 reactions with thioureas are also discussed.
- Ochiai, Masahito,Yamamoto, Shinji,Suefuji, Takashi,Chen, Da-Wei
-
p. 2753 - 2756
(2007/10/03)
-
- Reaction of Grignard compounds with 4-chloro-2-methyl-3-butyn-2-ol in Diethyl Ether equivalents
-
Reactions of RMgX · THF complexes with 4-chloro-2-methyl-3-butyn-2-ol in aromatic hydrocarbons were studied. The complexes formed by arylmagnesium halides require the presence of anisole for the reaction to occur. 4-Chloro-2-methyl-3-butyn-2-ol can be synthesized by reaction of 2-methyl-3-butyn-2-ol with sodium hypochloride in the two-phase system water-benzene.
- Shchelkunov,Sivolobova,Mataeva,Minbaev,Muldakhmetov
-
-
- A new and practical synthesis of vinyl dichlorides via a non-Wittig-type approach
-
A practical approach for the conversion of aldehydes to vinyl dichlorides has been developed. These are three-step, one-pot reactions involving the formation of trichlorocarbinol by treatment of aldehydes with trichloroacetic acid and sodium trichloroacetate followed by in situ protection and elimination reactions to form the desired vinyl dichlorides in 85 to 95% yields. (C) 2000 Dupont Pharmaceuticals Company.
- Wang, Zhe,Campagna, Silvio,Xu, Guoyou,Pierce, Michael E.,Fortunak, Joseph M.,Confalone, Pat N.
-
p. 4007 - 4009
(2007/10/03)
-
- Thermal decomposition of alkenyliodonium tetrafluoroborates: A novel route to fluoroalkenes
-
Alkenyl(phenyl)iodonium tetrafluoroborates dissolved in chloroform, or in the solid state, decompose thermally at 60°C to yield fluoroalkenes and iodobenzene as major products via an S(N)1- or S(N)2-type reaction within the ion pair of the substrates. (C) 2000 Elsevier Science Ltd.
- Okuyama, Tadashi,Fujita, Morifumi,Gronheid, Roel,Lodder, Gerrit
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p. 5125 - 5129
(2007/10/03)
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- Formamides undergo in-plane bimolecular nucleophilic vinylic substitutions (S(N)2) by the reaction with (E)-alkenyl(phenyl)iodonium tetrafluoroborates: Stereoselective synthesis of (Z)-vinyl formates
-
Reported for the first time is the stereoselective synthesis of (Z)-vinyl formates, which involves in-plane bimolecular nucleophilic vinylic substitutions of (E)-β-alkylvinyl(phenyl)iodonium tetrafluoroborates with formamides.
- Ochiai, Masahito,Yamamoto, Shinji,Sato, Koichi
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p. 1363 - 1364
(2007/10/03)
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- Chromium(ii)-mediated reactions of iodonium tetrafluoroborates with aldehydes: Umpolung of reactivity of diaryl-, alkenyl(aryl)-, and alkynyl(aryl)iodonium tetrafluoroborates
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The method described herein allows us, for the first time, to perform umpolung of reactivity of diaryl-, alkenyl(aryl)-, and alkynyl(aryl)iodonium tetrafluoroborates. The method involves generation of organochromium(III) species via reaction of iodonium salts with anhydrous chromium dichloride, followed by their nucleophilic addition to aldehydes to yield alcohols. In contrast to the reaction of aryl and alkenyl halides with chromium dichloride, these iodonium salts are so active that organochromium(III) could be generated without using a nickel catalyst. Substituent effects of unsymmetrically substituted diaryliodonium salts on the product profiles are in good agreement with the reported mode of decomposition of the intermediate unsymmetrical diaryliodanyl radicals. Alkenyl(mesityl)iodonium tetrafluoroborates undergo exclusive alkenylation of aldehydes with no signs of the formation of an arylation product.
- Chen, Da-Wei,Ochiai, Masahito
-
p. 6804 - 6814
(2007/10/03)
-
- Vinylic SN2 Reaction of 1-Decenyliodonium Salt with Halide Ions
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Reactions of (E)-1-decenyl(phenyl)iodonium salt with halide ions are examined under various conditions. The products are those of substitution and elimination, usually (Z)-1-halo-1-decene and 1-decyne, as well as iodobenzene, except for the reaction with fluoride which leads exclusively to elimination. The labeling experiments show that the elimination induced by fluoride occurs via an α mode, while that caused by the other halides is a syn β elimination. Kinetic results show that the substitution and β elimination occur mainly from the halo-λ3 -iodane intermediate; the substitution occurs as a bimolecular reaction with the external halide ion while the elimination is a unimolecular (intramolecular) reaction. The imermediacy of the hypervalent λ3-iodane as well as of the iodate are also confirmed by UV spectroscopy. The secondary kinetic isotope effects, leaving group substituent effects, and pressure effects on the rate are compatible with the in-plane vinylic SN2 mechanism for the substitution with inversion. Some retained substitution product, (E)-1-halo-1-decene, is formed in polar protic solvents like trifluoroacetic acid, formic acid, and 1,1,1,3,3,3-hexafluoro-2-propanol. The reaction is very slow in these solvents and no sign of formation of ionic intermediates is found. This slow substitution with retention is considered to occur via ligand coupling within the halo-λ3-iodane intermediate.
- Okuyama, Tadashi,Takino, Tomoki,Sato, Koichi,Oshima, Kunio,Imamura, Shohei,Yamataka, Hiroshi,Asano, Tsutomu,Ochiai, Masahito
-
p. 243 - 257
(2007/10/03)
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- In-plane vinylic S(N)2 substitution and intramolecular β elimination of β-alkylvinyl(chloro)-λ3-iodanes
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The reactions of four (E)-β-alkylvinyl(phenyl)iodonium salts with chloride ion were examined in acetonitrile and in several other solvents at 25°C. The β-methyl-, β-octyl-, and β-isopropyl-substituted iodonium salts undergo competitive bimolecular nucleophilic substitution to form the corresponding (Z)-1-chloro-1-alkene with inversion of configuration at the vinylic carbon and elimination to form the 1-alkyne. The β-tert-butyl-substituted iodonium salt affords only the products of the elimination reaction. The UV absorption spectra of the reactants show the rapid coversion of chloride and iodonium ions to an equilibrium mixture of the corresponding chloro-λ3-iodane, with an association constant of 5600-7600 mol-1 dm3. A kinetic analysis shows that most of the substitution and elimination products form from reaction of the λ3-iodane. Evidence is presented that the substitution reaction proceeds by a concerted bimolecular S(N)2 mechanism and that the elimination reaction proceeds by a unimolecular reaction mechanism with intramolecular transfer of the β-proton to the leaving group.
- Okuyama, Tadashi,Takino, Tomoki,Sato, Koichi,Ochiai, Masahito
-
p. 2275 - 2282
(2007/10/03)
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- Conversion of alkyl- and arylallenes into 1-alkynes through metallated intermediates
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A number of acetylenes RCH2C≡CH have been obtained by metallation of the allenes RCH=C=CH2 or mixtures of acetylenes and allenes with n-BuLi in THF-hexane and hydrolysis after allowing the metallated allenes to rearrange at roam temperature or by heating under reflux.
- Taherirastgar,Brandsma
-
p. 4035 - 4040
(2007/10/03)
-
- A Novel Transformation of Esters to Alkynes with 1-Substituted Benzotriazoles
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Reactions of lithio benzotriazol-1-yl derivatives 2, 11, and 25 with aromatic and aliphatic esters 3, 12, and 26 gave α-(benzotriazol-l-yl) ketones 4, 13, and 27, respectively, in high yields. Alternatively, α-(benzotriazol-l-yl) ketones 22 can be accessed by the reaction of α-(benzotriazol-1-yl) esters 20 with Grignard reagents. Condensation of 4, 13, 22, and 27 with (p-toluenesulfonyl)hydrazine provided p-tosylhydrazones 5, 14, 21, and 28. Treatment of hydrazones 5, 21, and 28 with n-butyllithium in diethyl ether resulted in the elimination of the tosyl group, dinitrogen, and benzotriazolyl group to afford the corresponding acetylenes 9, 23, and 29 in good yields. When α-(benzotriazol-l-yl) 1-α-phenoxy hydrazones 14 were treated with methyllithium, n-butyllithium, or phenyllithium, alkynes 18 were obtained, in which phenoxy groups were replaced by the lithium reagents.
- Katritzky, Alan R.,Wang, Jin,Karodia, Nazira,Li, Jianqing
-
p. 4142 - 4147
(2007/10/03)
-
- Triisopropylsilanol: A new type of phase transfer catalyst for dehydrohalogenation
-
A new solid-liquid phase transfer catalyst, trisopropylsilanol (TIPSOH), has been developed which, through the silanol/silanoate system, allows KOH to quantitatively convert even primary alkyl halides to alkenes avoiding both ether and alcohol by-products. Its potential application in the detoxification of mustard gas analogues and environmental pollutants has been demonstrated.
- Soderquist, John A.,Vaquer, Jaime,Diaz, Michael J.,Rane, Anil M.,Bordwell, Frederick G.,Zhang, Shizhong
-
p. 2561 - 2564
(2007/10/03)
-
- Synthesis and Nuclear Magnetic Resonance Studies on a Series of Synthesis Long-chain Tellurophene Fatty Esters
-
The synthesis and the results of the 1H and 13C NMR spectroscopic analyses of thirteen 2,5-disubstituted tellurophene fatty esters, containing substituents of different chain lengths, and of a monosubstituted tellurophene ester are repported.The tellurophene esters are obtained by cyclization of the corresponding conjugated intermediates with Na2Te in the presence of AgOAc in methanol.The tellurophene moiety in the alkyl chain induces a deshielding effect on the protons of the adjacent methylene prtons.The shift parameters of the tellurophene moiety on the shifts of the adjacent methylene carbon atoms are also determined.
- Jie, Marcel S. F. Lie Ken,Chau, Sherman H.
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p. 2642 - 2657
(2007/10/03)
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- Generation of Alkylidenecarbenes from 1,1-Dibromoalk-1-enes by the Reaction with Samarium Diiodide in Hexamethylphosphoric Triamide-Benzene
-
Reaction of 1,1-dibromoalk-1-enes with samarium diiodide in benzene containing 10percent of hexamethylphosphoric triamide (HMPA) affords rearranged alkynes; generation of alkylidenecarbenes is probably involved.
- Kunishima, Munetaka,Hioki, Kazuhito,Ohara, Takashi,Tani, Shohei
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p. 219 - 220
(2007/10/02)
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- Stabilized lithium acetylide and reactions therewith
-
A process for the preparation of ethynyl carbinols of the formula: STR1 wherein R" is hydrogen, a substituted or unsubstituted aliphatic or aromatic hydrocarbon, R'" is a substituted or unsubstituted aliphatic or aromatic hydrocarbon or R" and R'" together to the carbon atom to which they are joined represent a steroid, which comprises the steps of A. reacting in a solvent system comprising an aromatic hydrocarbon, at least one lithium alkylamide selected from the group consisting of: STR2 wherein R is a hydrogen or lower alkyl, R' is hydrogen, lower alkyl, a substituted or unsubstituted aliphatic, alicyclic or aromatic hydrocarbon, x is an integer of 2 to 8, y and z are each 0 to 1, with acetylene to form a monolithium acetylide B. reacting in a solvent system comprising an aromatic hydrocarbon, the monolithium acetylene from Part A with a ketone of the formula R"R'"C=O, wherein R" and R'" are as hereinbefore defined, and then C. hydrolysing the reaction product of Part B to form the corresponding ethynyl carbinol compound.
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-
-
- Preparation of Allenic Sulfones and Allenes from the Selenosulfonation of Acetylenes
-
β-(Phenylseleno)vinyl sulfones 2 are readily obtained from the free-radical selenosulfonation of acetylenes.Compounds 2 isomerize to allyl sulfones 4 under base-catalyzed conditions in nearly quantitative yield, with high stereoselectivity favoring the Z configuration.Allyl sulfones 4 afford generally high yields of allenic sulfones 1 when subjected to oxidation with m-chloroperbenzoic acid or tert-butyl hydroperoxide, followed by selenoxide syn-elimination.The sulfone-stabilized anion intermediates in the isomerizations of 2 to 4 can be alkylated, deuterated,or silylated in the α-position prior to oxidation, providing allenic sulfones with an additional α-substituent.In some cases, spontaneous elimination of the phenylseleno group occurred, producing the allenic sulfone without the need for an oxidation step.Desulfonylation of allyl sulfones 4f, 4c, and 25 with sodium amalgam afforded vinyl selenides that were converted to allenes in moderate to good yields by oxidation-elimination.The copper catalyzed coupling of allyl sulfones 4 with Grignard reagents comprises an alternative route to vinyl selenide precursors of allenes.These procedures permit the synthesis of various α- and γ-substituted allenic sulfones and allenes from acetylenes.
- Back, Thomas G.,Krishna, M. Vijaya,Muralidharan, K. Raman
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p. 4146 - 4153
(2007/10/02)
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- REACTIONS OF VINYLSILANES WITH LEWIS ACID-ACTIVATED IODOSYLBENZENE: STEREOSPECIFIC SYNTHESIS OF VINYLIODONIUM TETRAFLUOROBORATES AND THEIR REACTIONS AS HIGHLY ACTIVATED VINYL HALIDES
-
Alkenyl(phenyl)iodonium tetrafluoroborates 3 were synthesized from alkenylsilanes 1 by the reaction with iodosylbenzene and boron trifluoride-diethyl ether or triethyloxonium tetrafluoroborate.The reaction proceeds stereospecifically with retention of configuration of 1.X-ray diffraction analysis of (4-tert-butylcyclohexenyl)phenyliodonium tetrafluoroborate (3b) revealed the highly ionic structure with the distorted T-shape arrangement.Iodonium salts 3 behave like the highly activated species of vinyl iodides due to the high leaving ability of the iodine(III) substituents.Thus, a variety of substituted olefins including α-cyano and α-nitro olefins, vinyl sulfides, vinyl halides and α,β-unsaturated esters, were synthesized from 3 under mild conditions.A ligand coupling mechanism via the formation of 10-I-3 intermediate 27 containing a copper(III) ligand is proposed for the substitutions of 3 with nucleophiles.
- Ochiai, Masahito,Sumi, Kenzo,Takaoka, Yoshikazu,Kunishima, Munetaka,Nagao, Yoshimitsu,et al.
-
p. 4095 - 4112
(2007/10/02)
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- Dehydrosilylation of Alkenylsilanes Utilizing Polyvalent Organoiodine Compounds
-
Alkenylsilanes, on treatment with iodosylbenzene activated by co-ordination of boron trifluoride-diethyl ether to the oxygen atom, give the corresponding alkynes in good to excellent yields, presumably via vinyliodine(III) intermediates.
- Ochiai, Masahito,Sumi, Kenzo,Nagao, Yoshimitsu,Fujita, Eiichi,Arimoto, Masao,Yamaguchi, Hideo
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p. 697 - 699
(2007/10/02)
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- Selective Synthesis of Alkynes by Catalytic Dehydrogenation of Alkenes over Polymer-supported Palladium Acetate in the Liquid Phase
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A heterogenized palladium acetate catalyst, in the presence of oxygen and perchloric acid in ethanol-water caused the direct conversion of terminal and internal monoalkenes into the corresponding alkynes, under mild conditions and in high yields; Wacker-type ketonization occurs with the same reagents in dioxane-water.
- Cum, Giampietro,Gallo, Raffaele,Ipsale, Salvatore,Spadaro, Agatino
-
p. 1571 - 1573
(2007/10/02)
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- AN EFFICIENT COUPLING REACTION OF ANIONIC PROPARGYL AND ORGANIC HALIDES
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The organometallic produced by controlled lithiation of allene functions as an efficient propargylic anion equivalent in coupling reactions with alkyl and allyl halides.
- Hooz, John,Calzada, Jose G.,McMaster, Denis
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p. 271 - 274
(2007/10/02)
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- VINYLIODONIUM SALTS: THEIR STEREOSPECIFIC SYNTHESIS AND REACTIONS AS THE ACTIVATED VINYL HALIDES
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Vinyliodonium salts 2 were synthesized from vinylsilanes 1 by the reaction with iodosylbenzene and triethyloxonium tetrafluoroborate.The reaction occurs stereospecifically with retention of configuration.Vinyliodonium salts 2 are highly effective as the activated species of vinyl iodides.Thus, a variety of substituted olefins including α-cyano and α-nitro olefins, vinyl sulfides, vinyl halides, and α,β-unsaturated esters, were prepared from 2 under mild reaction conditions.
- Ochiai, Masahito,Sumi, Kenzo,Nagao, Yoshimitsu,Fujita, Eiichi
-
p. 2351 - 2354
(2007/10/02)
-
- Poly(ethylene glycols) and Poly(ethylene glycol)-Grafted Copolymers Are Extraordinary Catalysts for Dehydrohalogenation under Two-Phase and Three-Phase Conditions
-
Poly(ethylene glycols) 3> possess remarkably high activity as catalysts for dehydrohalogenation in organic-aqueous hydroxide two-phase systems, relative to classical phase-transfer agents, i. e., benzyltriethylammonium chloride and 18-crown-6.The importance of terminal hydroxyl groups together with the abrupt increase in catalyst activity and concentration in the organic layer on going from n=2 to n=3 and from n=3 to n=4 suggests the involvement of novel polymeric alkoxides I and/or hydroxides II.Moreover, the fact that maximum activity is obtained with n5 implies that an "18-crown-6-like" structure occuring at the terminus of the polymer chain is optimal for catalysis.Poly(ethylene glycols) grafted to cross-linked polystyrene display reasonably high activity.In preparative-scale conversions, such triphase catalysts can be recovered quantitatively by simple filtration and reused without significant loss in activity.
- Kimura, Yoshikazu,Regen, Steven L.
-
p. 195 - 198
(2007/10/02)
-
- Poly(ethylene glycols) Are Extraordinary Catalysts in Liquid-Liquid Two-Phase Dehydrohalogenation
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Poly(ethylene glycols) 3> are highly active and selective in catalyzing dehydrohalogenation in organic-aqueous hydroxide two-phase systems.
- Kimura, Yoshikazu,Regen, Steven L.
-
p. 2493 - 2494
(2007/10/02)
-
- Application of Phase Transfer Catalysis, 14.- Preparation of Alkynes from Halides with Solid Potassium tert-Butoxide and Crown Ether
-
Preparatively very simple and mild HX eliminations with solid potassium tert-butoxide in petroleum ether in the presence of catalytic amounts of crown-6 are described. 1,2-Dihalides (from alkenes) and 1,1-dihalides (from aldehydes) yield 1-alkynes; internal geminal dihalides (from symmetric ketones) give internal alkynes in excellent yields. 2,2-Dihalides (from methyl ketones) yield homogeneous 1-alkynes only if the 3-position is blocked. (E)-Haloalkenes lead also to alkynes in a syn-elimination process.
- Dehmlow, Eckehard V.,Lissel, Manfred
-
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