- Catalytic, contra-Thermodynamic Positional Alkene Isomerization
-
The positional isomerization of C═C double bonds is a powerful strategy for the interconversion of alkene regioisomers. However, existing methods provide access to thermodynamically more stable isomers from less stable starting materials. Here, we report
- Occhialini, Gino,Palani, Vignesh,Wendlandt, Alison E.
-
supporting information
p. 145 - 152
(2022/01/19)
-
- Contra-Thermodynamic Positional Isomerization of Olefins
-
A light-driven method for the contra-thermodynamic positional isomerization of olefins is described. In this work, stepwise PCET activation of a more substituted and more thermodynamically stable olefin substrate is mediated by an excited-state oxidant an
- Zhao, Kuo,Knowles, Robert R.
-
supporting information
p. 137 - 144
(2022/01/19)
-
- Nickel-catalyzed reductive deoxygenation of diverse C-O bond-bearing functional groups
-
We report a catalytic method for the direct deoxygenation of various C-O bond-containing functional groups. Using a Ni(II) pre-catalyst and silane reducing agent, alcohols, epoxides, and ethers are reduced to the corresponding alkane. Unsaturated species including aldehydes and ketones are also deoxygenated via initial formation of an intermediate silylated alcohol. The reaction is chemoselective for C(sp3)-O bonds, leaving amines, anilines, aryl ethers, alkenes, and nitrogen-containing heterocycles untouched. Applications toward catalytic deuteration, benzyl ether deprotection, and the valorization of biomass-derived feedstocks demonstrate some of the practical aspects of this methodology.
- Cook, Adam,MacLean, Haydn,St. Onge, Piers,Newman, Stephen G.
-
p. 13337 - 13347
(2021/11/20)
-
- Construction of C-C Bond via C-N and C-O Cleavage
-
The construction of a C-C bond is a center subject in synthetic organic chemistry. The cross-electrophile coupling has provided a powerful tool to forge the C-C bond. However, this process generally requires organic halides, which has severely restricted
- He, Rong-De,Pang, Xiaobo,Shu, Xing-Zhong
-
p. 635 - 640
(2020/04/07)
-
- Action of Organoaluminum Reagents on Esters: Alkene Production and the Degradation of Synthetic Lubricants
-
Reactions of methylaluminum reagents with ester-based lubricating oils are mimicked through the reaction of trimethylaluminum (TMA) with tetraesters C(CH2OC(O)R)4 (R = C5H11 4Pent, Bn 4Bn). Using a 2:1 stoichiometry gave adduct 4Pent(TMA)4. NMR spectroscopy on 1:1-12:1 TMA/4Pent systems suggested 4Pent gave dimethylated adduct C5H11CMe2OAlMe2(TMA), 2Pent(TMA). Similar combination of TMA with 4Bn at raised temperatures transformed 4Bn into C(CH2OAlMe2)4(2Bn)4 5(2Bn)4 by sequential reaction of each ester group. Doubly reacted {BnC(O)OCH2}2C(CH2OAlMe2)2(2Bn)2 7Bn(2Bn)2 was isolated and characterized. A Mitsubishi molecule could also be isolated, its formation rationalized by the elimination of 2Bn and TMA from 5(2Bn)4. The action of MenAlCl3-n (n = 1, 1.5, 2) was studied initially on monoester BnC(O)OMe 1Bn. Combining excess Me2AlCl with 1Bn gave adduct 1Bn(Me2AlCl) and small amounts of dimethylated BnCMe2OAlMe2(Me2AlCl), 2Bn(Me2AlCl), and MeOAlCl2 10. 2Bn(Me2AlCl) was fully characterized and, in the presence of 10, acted as a source of 2Bn(MeAlCl2). From this species, a mixture of alkenes could be generated by formal elimination of Me3Al2(OH)Cl2 13, the decomposition of which was presumed to also explain MeH observation. Replacing Me2AlCl with aluminum sesquichloride or MeAlCl2 led to progressively more sluggish but similar reactions. Using MenAlCl3-n (n = 1, 1.5, 2) with tetraesters suggested similar reactivity to monoesters.
- Slaughter, Jonathan,Molyneux, Samuel A.,Peel, Andrew J.,Wheatley, Andrew E. H.
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p. 395 - 408
(2019/01/11)
-
- Synthesis of Functionalized α-Vinyl Aldehydes from Enaminones
-
An efficient RhII-catalyzed synthesis of functionalized α-vinyl aldehydes with high E/Z stereoselectivity was developed. The reaction mediates the cyclopropanation of enaminones with vinyl carbenoids that are generated from cyclopropenes in situ to give the aminocyclopropane intermediates. Selective C?C bond cleavage of the cyclopropane intermediates leads to formation of α-vinyl aldehyde derivatives with high E/Z selectivity. This method proceeds at room temperature under very mild reaction conditions and works with a broad substrate scope.
- Chen, Jie,Guo, Pan,Zhang, Jianguo,Rong, Jiaxin,Sun, Wangbin,Jiang, Yaojia,Loh, Teck-Peng
-
supporting information
p. 12674 - 12679
(2019/08/07)
-
- Copper-Catalyzed Enantio- and Diastereoselective Addition of Silicon Nucleophiles to 3,3-Disubstituted Cyclopropenes
-
A highly stereocontrolled syn-addition of silicon nucleophiles across cyclopropenes with two different geminal substituents at C3 is reported. Diastereomeric ratios are excellent throughout (d.r.≥98:2) and enantiomeric excesses usually higher than 90 %, even reaching 99 %. This copper-catalyzed C?Si bond formation closes the gap of the direct synthesis of α-chiral cyclopropylsilanes.
- Zhang, Liangliang,Oestreich, Martin
-
supporting information
p. 14304 - 14307
(2019/11/13)
-
- Nucleophilic Substitutions of Alcohols in High Levels of Catalytic Efficiency
-
A practical method for the nucleophilic substitution (SN) of alcohols furnishing alkyl chlorides, bromides, and iodides under stereochemical inversion in high catalytic efficacy is introduced. The fusion of diethylcyclopropenone as a simple Lewis base organocatalyst and benzoyl chloride as a reagent allows notable turnover numbers up to 100. Moreover, the use of plain acetyl chloride as a stoichiometric promotor in an invertive SN-type transformation is demonstrated for the first time. The operationally straightforward protocol exhibits high levels of stereoselectivity and scalability and tolerates a variety of functional groups.
- Stach, Tanja,Dr?ger, Julia,Huy, Peter H.
-
supporting information
p. 2980 - 2983
(2018/05/28)
-
- CATALYSTS AND METHODS FOR FORMING ALKENYL AND ALKYL SUBSTITUTED ARENES
-
Embodiments of the present disclosure provide for Rh(I) catalysts, methods of making alkenyl substituted arenes (e.g., allyl arene, vinyl arene, and the like), methods of making alkyl substituted arenes, and the like.
- -
-
Paragraph 0157
(2018/03/25)
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- Reactivity of a Palladacyclic Complex: A Monodentate Carbonate Complex and the Remarkable Selectivity and Mechanism of a Neophyl Rearrangement
-
The ligand N(CH2-2-C5H4N)2(CH2CH2CH2OH), L1, reacted with [Pd(CH2CMe2C6H4)(COD)] to give a new fluxional cycloneophyl organopalladium complex [Pd(CH2CMe2C6H4)(κ2-L1)], 1, which on attempted recrystallization from THF gave the monodentate carbonate complex [Pd(CO3)(κ3-L1)], 2. Complex 2 was prepared in designed syntheses by reaction of [PdCl(κ3-L1)]+ with silver carbonate or by reaction of [Pd(OH)(κ3-L1)]+ with CO2. Complex 1 reacted with aqueous CO2 to give the cationic neophylpalladium complex [Pd(CH2CMe2C6H5)(κ3-L1)]+(HCO3)-, 6. Complex 6 reacts with hydrogen peroxide to give complex 2 with release of a mixture of organic products, the major one being 2-phenyl-2-butanol, PB. The formation of PB involves a neophyl rearrangement with the unprecedented preference for methyl over phenyl migration. A mechanistic basis for this unexpected reaction is proposed, involving β-carbon elimination at a palladium(IV) center.
- Behnia, Ava,Fard, Mahmood A.,Blacquiere, Johanna M.,Puddephatt, Richard J.
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p. 4759 - 4769
(2018/02/07)
-
- Photocatalytic Transfer Hydrogenolysis of Allylic Alcohols on Pd/TiO2: A Shortcut to (S)-(+)-Lavandulol
-
We report herein a regio- and stereoselective photocatalytic hydrogenolysis of allylic alcohols to form unsaturated hydrocarbons employing a palladium(II)-loaded titanium oxide; the reaction proceeds at room temperature under light irradiation without stoichiometric generation of salt wastes. Olefin and saturated alcohol moieties tolerated the reaction conditions. Hydrogen atoms were selectively incorporated into less sterically congested carbons of the allylic functionalities. This protocol allowed a short-step synthesis of (S)-(+)-lavandulol from (R)-(?)-carvone by avoiding otherwise necessary protection/deprotection steps.
- Takada, Yuki,Caner, Joaquim,Kaliyamoorthy, Selvam,Naka, Hiroshi,Saito, Susumu
-
supporting information
p. 18025 - 18032
(2017/12/08)
-
- A Zinc Catalyzed C(sp3)?C(sp2) Suzuki–Miyaura Cross-Coupling Reaction Mediated by Aryl-Zincates
-
The Suzuki–Miyaura (SM) reaction is one of the most important methods for C?C bond formation in chemical synthesis. In this communication, we show for the first time that the low toxicity, inexpensive element zinc is able to catalyze SM reactions. The cross-coupling of benzyl bromides with aryl borates is catalyzed by ZnBr2, in a process that is free from added ligand, and is compatible with a range of functionalized benzyl bromides and arylboronic acid pinacol esters. Initial mechanistic investigations indicate that the selective in situ formation of triaryl zincates is crucial to promote selective cross-coupling reactivity, which is facilitated by employing an arylborate of optimal nucleophilicity.
- Procter, Richard J.,Dunsford, Jay J.,Rushworth, Philip J.,Hulcoop, David G.,Layfield, Richard A.,Ingleson, Michael J.
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p. 15889 - 15893
(2017/10/24)
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- Toward a mild dehydroformylation using base-metal catalysis
-
Dehydroformylation, or the reaction of aldehydes to produce alkenes, hydrogen gas, and carbon monoxide, is a powerful transformation that is underdeveloped despite the high industrial importance of the reverse reaction, hydroformylation. Interestingly, nature routinely performs a related transformation, oxidative dehydroformylation, in the biosynthesis of cholesterol and related sterols under mild conditions using base-metal catalysts. In contrast, chemists have recently developed a non-oxidative dehydroformylation method; however, it requires high temperatures and a precious-metal catalyst. Careful study of both approaches has informed our efforts to design a base-metal catalyzed, mild dehydroformylation method that incorporates benefits from each while avoiding several of their respective disadvantages. Importantly, we show that cooperative base metal catalysis presents a powerful, mechanistically unique approach to reactions which are difficult to achieve using conventional catalyst design.
- Abrams, Dylan J.,West, Julian G.,Sorensen, Erik J.
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p. 1954 - 1959
(2017/03/09)
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- Tandem Hydroalumination/Cu-Catalyzed Asymmetric Vinyl Metalation as a New Access to Enantioenriched Vinylcyclopropane Derivatives
-
Herein, we report the first enantio- and diastereoselective addition of stereodefined vinyl organometallic reagents to cyclopropenes. The operationally simple tandem hydroalumination and copper-catalyzed vinylmetalation allows for the unique access of a diverse set of enantioenriched vinylcyclopropane derivatives.
- Müller, Daniel S.,Werner, Veronika,Akyol, Sema,Schmalz, Hans-Günther,Marek, Ilan
-
supporting information
p. 3970 - 3973
(2017/08/14)
-
- Rh(II)-Catalyzed [2,3]-Sigmatropic Rearrangement of Sulfur Ylides Derived from Cyclopropenes and Sulfides
-
(Chemical Equation Presented) A new type of Rh2(OAc)4-catalyzed [2,3]-sigmatropic rearrangement of sulfur ylides is reported. A series of cyclopropenes were successfully employed for [2,3]-sigmatropic rearrangement by a reaction with either allylic or propargylic sulfides. Under the optimized conditions, the reaction afforded the products in moderate to excellent yields. In these transformations, the vinyl metal carbenes generated in situ from the cyclopropenes were effectively trapped by sulfides, resulting in the formation of corresponding products upon [2,3]-sigmatropic rearrangements.
- Zhang, Hang,Wang, Bo,Yi, Heng,Zhang, Yan,Wang, Jianbo
-
supporting information
p. 3322 - 3325
(2015/07/15)
-
- Asymmetric Copper-Catalyzed Carbozincation of Cyclopropenes en Route to the Formation of Diastereo- and Enantiomerically Enriched Polysubstituted Cyclopropanes
-
The enantioselective synthesis of cyclopropylzinc reagents has been achieved via a copper-catalyzed carbozincation of 3,3-disubstituted cyclopropenes with diorganozinc reagents. The obtained organozinc compounds can be easily functionalized with a broad range of electrophiles, including palladium-catalyzed cross-couplings, affording highly substituted cyclopropanes. The operationally simple procedure using very low quantities of a commercially available and inexpensive copper catalyst provides a new tool for the synthesis of highly enantioenriched cyclopropanes as single diastereoisomers.
- Müller, Daniel S.,Marek, Ilan
-
supporting information
p. 15414 - 15417
(2015/12/26)
-
- Biphilic organophosphorus catalysis: Regioselective reductive transposition of allylic bromides via PIII/PV redox cycling
-
We report that a regioselective reductive transposition of primary allylic bromides is catalyzed by a biphilic organophosphorus (phosphetane) catalyst. Spectroscopic evidence supports the formation of a pentacoordinate (σ5-P) hydridophosphorane as a key reactive intermediate. Kinetics experiments and computational modeling are consistent with a unimolecular decomposition of the σ5-P hydridophosphorane via a concerted cyclic transition structure that delivers the observed allylic transposition and completes a novel PIII/PV redox catalytic cycle. These results broaden the growing repertoire of reactions catalyzed within the PIII/PV redox couple and suggest additional opportunities for organophosphorus catalysis in a biphilic mode.
- Reichl, Kyle D.,Dunn, Nicole L.,Fastuca, Nicholas J.,Radosevich, Alexander T.
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p. 5292 - 5295
(2015/05/13)
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- METHODS FOR OBTAINING OPTICALLY ACTIVE EPOXIDES AND VICINAL DIOLS FROM 2,2-DISUBSTITUTED EPOXIDES
-
The invention provides yeast strains, and polypeptides encoded by genes of such yeast strains, that have enantiospecific 2,2-disubstituted epoxide hydrolase activity. The invention also features nucleic acid molecules encoding such polypeptides, vectors c
- -
-
Paragraph 0124
(2015/12/19)
-
- Palladium-catalyzed regioselective azidation of allylic C-H bonds under atmospheric pressure of dioxygen
-
A palladium-catalyzed allylic azidation of alkenes with sodium azide under atmospheric pressure of dioxygen was developed. This methodology provides a new efficient and simple route for accessing allylic azides. Furthermore, the one-pot process consisting of Pd-catalyzed allylic azidation of alkenes and Cu-catalyzed 1,3-dipolar cycloaddition led directly to the 1,2,3-triazole from the alkene. The formed allylic azide can be also in situ reduced to the allylic amine or oxidized to the alkenyl nitrile. the Partner Organisations 2014.
- Chen, Huoji,Yang, Wanfei,Wu, Wanqing,Jiang, Huanfeng
-
supporting information
p. 3340 - 3343
(2014/05/20)
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- Pd-catalyzed ligand-free Suzuki reaction of β-substituted allylic halides with arylboronic acids in water
-
The catalyst system consisting of Pd(TFA)2 and KOH allows for a wide range of β-substituted allylic halides to react efficiently with various arylboronic acids in neat water under ligand-free conditions, affording the allylated arenes in high yields with broad functional group tolerance and up to 7.4 × 105 TON and 15416 h-1 TOF.
- Dong, Chaonan,Zhang, Lingjuan,Xue, Xiao,Li, Huanrong,Yu, Zhiyong,Tang, Weijun,Xu, Lijin
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p. 11152 - 11158
(2014/03/21)
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- Gold-catalyzed allylation of aryl boronic acids: Accessing cross-coupling reactivity with gold
-
A sp3-sp2 C?C cross-coupling reaction catalyzed by gold in the absence of a sacrificial oxidant is described. Vital to the success of this method is the implementation of a bimetallic catalyst bearing a bis(phosphino)amine ligand. A mechanistic hypothesis is presented, and observable transmetalation, C?Br oxidative addition, and C?C reductive elimination in a model gold complex are shown. We expect that this method will serve as a platform for the development of novel transformations involving redox-active gold catalysts.
- Levin, Mark D.,Toste, F. Dean
-
supporting information
p. 6211 - 6215
(2014/06/23)
-
- Aryl radical formation by copper(I) photocatalyzed reduction of diaryliodonium salts: NMR Evidence for a CuII/CuI mechanism
-
Photocatalyzed reduction of diaryliodonium salts was achieved by using [Cu(dpp)2][PF6] as a photoactive complex and DIPEA as a reductive quench. The application of a copper catalyst allows the generation of aryl radicals under mild conditions and maintains their reactivity for C-C bond formation processes.
- Baralle, Alexandre,Fensterbank, Louis,Goddard, Jean-Philippe,Ollivier, Cyril
-
supporting information
p. 10809 - 10813
(2013/09/02)
-
- Visible-light photocatalytic reduction of sulfonium salts as a source of aryl radicals
-
Triarylsulfonium salts are prompted to undergo efficient homolytic reduction by single electron transfer under mild photocatalytic conditions. The liberated aryl radical can then participate in carbon-carbon bond formation processes with allyl sulfones and activated olefins. Triarylsulfonium salts emerge as a valuable and alternative source of aryl radicals for synthesis. Copyright
- Donck, Simon,Baroudi, Abdulkader,Fensterbank, Louis,Goddard, Jean-Philippe,Ollivier, Cyril
-
supporting information
p. 1477 - 1482
(2013/06/27)
-
- Graphite oxide activated zeolite NaY: Applications in alcohol dehydration
-
A mixture of graphite oxide (GO) and the zeolite NaY (Si/Al = 5.1) was used to dehydrate various alcohols to their respective olefinic products. Using conditions optimized for 4-heptanol (15 wt% GO-NaY (1 : 1 wt/wt), 150°C, 30 min), a series of secondary and tertiary aliphatic alcohols were cleanly dehydrated in moderate to excellent conversions (27.5-97.2%). Several primary alcohols were also dehydrated, although higher catalyst loadings (200 wt% GO-NaY (1 : 1) and longer reaction times (3 h) were required. The enhanced dehydration activity was attributed to the ability of GO to convert NaY to an acidic form and without the need for ammonium cation exchange and/or high temperature calcination. The Royal Society of Chemistry 2013.
- Todd, Alexander D.,Bielawski, Christopher W.
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p. 135 - 139
(2013/03/29)
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- Unique catalysis of gold nanoparticles in the chemoselective hydrogenolysis with H2: Cooperative effect between small gold nanoparticles and a basic support
-
Gold nanoparticles on hydrotalcite act as a heterogeneous catalyst for the chemoselective hydrogenolysis of various allylic carbonates to the corresponding terminal alkenes using H2 as a clean reductant. The combination of gold nanoparticles and basic supports elicited significantly unique and selective catalysis in the hydrogenolysis.
- Noujima, Akifumi,Mitsudome, Takato,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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p. 6723 - 6725
(2012/07/28)
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- Facile η5-η3 hapticity interconversion in pentamethylcyclopentadienyl ruthenium(ii) complexes containing a phenylmethallyl ("open indenyl") ligand
-
The indenyl effect has been introduced to pentadienyl ("open cyclopentadienyl") chemistry by preparation of the phenylmethallyl ("open indenyl") ligand oIndMe. The reaction of its potassium salt K(oIndMe) with [(η5-C 5Me5)RuCl]4 afforded the sandwich complex [(η5-C5Me5)Ru(η5-oInd Me)] (1), which, upon treatment with PMe3, CO, and 2,6-dimethylphenyl isocyanide (CN-o-Xy), easily underwent η5- η3 hapticity interconversion and formed the complexes [(η5-C5Me5)Ru(η3-oInd Me)(L)] (2, L = PMe3; 3, L = CO; 4, L = CN-o-Xy). In these complexes, the η3-bound phenylmethallyl ligand adopts an anti-conformation with regard to the relative positions of the phenyl and methyl substituents. For the PMe3 complex anti-2, slow conversion to the syn-isomer was observed, and this equilibrium reaction was monitored by NMR spectroscopy at 50 °C to determine a first order rate constant of k 323 K = 6.57 × 10-6 (± 0.02 × 10 -6) s-1 and an activation barrier of ΔG° = 26.8 kcal mol-1. DFT calculations afforded a stabilization of syn-2 and syn-3 by ΔG298 = -1.54 and -1.74 kcal mol-1 over the respective anti-isomer.
- Gloeckner, Andreas,Arias, Oscar,Bannenberg, Thomas,Daniliuc, Constantin G.,Jones, Peter G.,Tamm, Matthias
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scheme or table
p. 11511 - 11518
(2012/01/04)
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- Palladium-catalyzed desulfinylative C-C allylation of Grignard reagents and enolates using allylsulfonyl chlorides and esters
-
2-Methylprop-2-ene-, prop-2-ene-, 1-methylprop-2-ene-, and (E)-but-2-enesulfonyl chlorides have been used as electrophilic partners in desulfinylative palladium-catalyzed C-C coupling with Grignard reagents and sodium salts of dimethyl malonate and methyl
- Rao Volla, Chandra M.,Dubbaka, Srinivas Reddy,Vogel, Pierre
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experimental part
p. 504 - 511
(2009/04/07)
-
- First cross-coupling reaction of potassium aryltrifluoroborates with organic chlorides in aqueous media catalyzed by an oxime-derived palladacycle
-
(Chemical Equation Presented) Potassium aryltrifluoroborates are cross-coupled with aryl and heteroaryl chlorides using a 4-hydroxyacetophenone oxime-derived palladacycle as precatalyst, K2CO3 as base, and TBAB as additive in refluxing water under conventional and microwave heating affording the corresponding biphenyls under phosphine-free conditions. For the arylation of allyl and benzyl chlorides, KOH is used as base in acetone-water (3:2) at rt or 50 °C using 0.1 mol % Pd loading providing allylbenzenes and diarylmethanes, respectively.
- Alacid, Emilio,Najera, Carmen
-
supporting information; scheme or table
p. 5011 - 5014
(2009/05/31)
-
- Methods for Obtaining Optically Active Epoxides and Vicinal Diols From 2,2-Disubstituted Epoxides
-
The invention provides yeast strains, and polypeptides encoded by genes of such yeast strains, that have enantiospecific 2,2-disubstituted epoxide hydrolase activity. The invention also features nucleic acid molecules encoding such polypeptides, vectors containing such nucleic acid molecules, and cells containing such vectors. Also embraced by the invention are methods for obtaining optically active 2,2-disubstituted vicinal diols and optically active 2,2-disubstituted epoxides.
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-
-
- A highly selective, high-speed, and hydrolysis-free O-acylation in subcritical water in the absence of a catalyst
-
(Chemical Equation Presented) Fast and furious: A wide range of alcohols are acylated by acetic anhydride, in the absence of catalyst, in subcritical water in a flow-type microreaction system. The esters are selectively produced in high yields at temperatures of 200 to 250°C. Varying the amount of acetic anhydride added with respect to the alcohols allows the regioselective acylation of one or both hydroxy groups of various dihydroxy compounds (see picture).
- Sato, Masahiro,Matsushima, Keiichiro,Kawanami, Hajime,Ikuhsima, Yutaka
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p. 6284 - 6288
(2008/04/05)
-
- Phenyl versus alkyl migration in the fragmentation of alkoxychlorocarbenes
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Phenyl versus methyl (alkyl) group migration is assessed in the fragmentations of neophyloxychlorocarbene, 2,2-diphenylpropyloxychlorocarbene, and 1-phenylcyclopropylmethoxychlorocarbene. Rate constants and activation parameters of the fragmentations are also reported.
- Moss, Robert A.,Fu, Xiaolin
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p. 235 - 237
(2007/10/03)
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- A remarkable catalytic activity of [Cu(NCMe)2(PPh 3)2]BF4 in conjugate addition of organomanganese reagents to α,β-unsaturated ester, enone and allyl chloride
-
A simple and convenient method of conjugate addition of alkyl and aryl organomanganese reagents to α,β-unsaturated ester and enone and allyl chloride in presence of Cu(I) salts is described. Conjugated products result with [Cu(NCMe)2(PPh3)2]BF4 as a catalyst along with chlorosilane as an accelerator at -10 to 0 °C.
- Deshmukh,Jadhav, Sunil,Anbhule,Mali,Suryawanshi
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p. 248 - 250
(2007/10/03)
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- A highly effective (Triphenyl phosphite)palladium catalyst for a cross-coupling reaction of allylic alcohols with organoboronic acids
-
The cross coupling reaction of aryl and vinyl boronic acids and allylic alcohols proceeded smoothly in toluene or dioxane in the presence of a (triphenyl phosphite)palladium catalyst to give the corresponding allylbenzene derivatives and 1,4-dienes. Neither cocatalysts for promoting C-O bond cleavage of allylic alcohols nor bases for activation of organoboron reagents are required for promoting the coupling process. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Kayaki, Yoshihito,Koda, Takashi,Ikariya, Takao
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p. 4989 - 4993
(2007/10/03)
-
- Simple deprotection of acetal type protecting groups under neutral conditions
-
Heating acetals with ethylene glycol causes the deprotection of acetal type protecting groups. When acetals such as MOM ethers, MEM ethers, and THP ethers were heated in ethylene glycol or propylene glycol, solvolysis proceeded smoothly to produce alcohols in excellent yield. This reaction is a very promising method for chemoselective deprotection of acetal type protecting groups.
- Miyake, Hideyoshi,Tsumura, Takatsugu,Sasaki, Mitsuru
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p. 7213 - 7215
(2007/10/03)
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- Suzuki-Miyaura and related cross-couplings in aqueous solvents catalyzed by di(2-pyridyl)methylamine-palladium dichloride complexes
-
Di(2-pyridyl)methylamine-based palladium dichloride complexes 4 are versatile catalysts for different types of cross-coupling reactions in water or aqueous solvents under aerobic conditions. The Suzuki-Miyaura reaction of arylboronic acids can be performed with bromoarenes under water reflux using K2CO3 as base or at room temperature or 60°C in aqueous methanol using KOH as base. For aryl chlorides the corresponding cross-couplings with arylboronic acids can be carried out in refluxing water with K2CO3 as base and TBAB as additive to provide biaryls and heterobiaryls. Arylboronic acids react with benzylic chlorides and allylic substrates such as chlorides, acetates or carbonates also in refluxing water with K2CO3 as base or at room temperature in aqueous acetone and KOH as base, to give diarylmethanes and arylpropenes. Trimethylboroxine and alkylboronic acids are coupled with bromo- and chloroarenes under water at reflux with K2CO3 as base and TBAB as additive to furnish methyl- and butylarenes. These cross-couplings have also been performed in shorter times under microwave irradiation. Several important intermediates such as, 4′-methylbiphenyl-2-carbonitrile, 4-biphenylacetic acid, 3-(3-methylphenyl)benzoic acid, 4,5-diphenyl-2-methyl- 3(2H)pyridazinone and 2-(4′-fluorobenzyl)thiophene have been prepared under aqueous and aerobic conditions in good yields.
- Najera, Carmen,Gil-Molto, Juan,Karlstroem, Sofia
-
p. 1798 - 1811
(2007/10/03)
-
- Cross-coupling reactions with boronic acids in water catalysed by oxime-derived palladacycles
-
Palladacycles derived from phenone-oximes 1 are efficient precatalysts for the Suzuki-Miyaura coupling of arylboronic acids with aromatic and heteroaromatic bromides and chlorides under water reflux under aerobic conditions. Alternatively, the coupling can also be carried out at room temperature in methanol-water. Aryl bromides gave biaryls with TON up to 105 and TOF up to 7 × 104 h-1. Activated and deactivated aryl chlorides need the presence of TBAB for the couplings, showing slightly lower efficiency (TON up to 9000 and TOF up to 3850 h-1). C(sp2)-C(sp3) bonds can also be formed by cross-coupling reactions of trimethylboroxine and butylboronic acid with aromatic bromides and chlorides under water reflux and of benzylic and allylic chlorides or acetates with arylboronic acids in acetone-water at room temperature.
- Botella, Luis,Nájera, Carmen
-
-
- Highly active oxime-derived palladacycle complexes for Suzuki-Miyaura and Ullmann-type coupling reactions
-
Oxime-derived chloro-bridged palladacycles 12 and 13 are efficient complexes for the Suzuki-Miyaura reactions of aryl-, allyl-, and benzyl halides with arylboronic acids. The isolated catalysts are thermally stable, not sensitive to air or moisture, and easily accessible from inexpensive starting materials. The reaction can be performed under aerobic conditions with aryl bromides and chlorides, displaying turnover numbers (TON) of up to 5 × 105 and turnover frequencies (TOF) of up to 198 000 h-1 for aryl bromides. Aryl chlorides undergo the Suzuki reaction with arylboronic acids with TON of up to 4700 and TOF up to 4700 h-1. Even inexpensive and readily available benzyl and allyl chlorides undergo the coupling reaction with good turnover numbers. Complexes of 12 catalyze the syntheses of symmetrical biaryls in good yields via reductive coupling of iodoarenes in the presence of Huenig's base.
- Alonso, Diego A.,Najera, Carmen,Pacheco, Ma Carmen
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p. 5588 - 5594
(2007/10/03)
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- Hydrodehalogenation of 1,1-dibromocyclopropanes by Grignard reagents promoted by titanium compounds
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1,1-Dibromocyclopropanes are converted into the corresponding monobromocyclopropanes (as mixtures of stereoisomers where appropriate) by reaction with 1.0-1.3 mol equiv. of ethylmagnesium bromide and 2-10 mol% titanium isopropoxide for 90%). With ethylmagnesium bromide, the reaction occurs very slowly in the absence of catalyst; with methylmagnesium bromide, the reaction does occur in the absence of catalyst, but is only slightly promoted in the presence of titanium isopropoxide. Reactions with a number of other Grignard reagents are also discussed. In the case of phenethylmagnesium bromide, the major product containing the phenethyl-group is ethylbenzene, together with small amounts of styrene and ethyl 4-phenyl-2-butyl ether, a product of trapping of the solvent, ether. In other cases, relatively large amounts of a diether, formally derived by hydrogen ion adjacent to the ether oxygen followed by dimerisation, are isolated. No products were identified incorporating the cyclopropane and either the Grignard alkyl group or the solvent. Labelling studies indicate that the hydrogen introduced into the cyclopropane is not derived from either the α- or β-positions of the Grignard reagent. When the reduction is carried out with phenethylmagnesium bromide in d8-tetrahydrofuran both monobromides contain deuterium.
- Dulayymi, Juma'a R. Al,Baird, Mark S.,Bolesov, Ivan G.,Nizovtsev, Alexey V.,Tverezovsky, Viacheslav V.
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p. 1603 - 1618
(2007/10/03)
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- Quantum Yields of the Initiation Step and Chain Propagation Turnovers in SRN1 Reactions: Photostimulated Reaction of 1-Iodo-2-methyl-2-phenyl Propane with Carbanions in DMSO
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Neophyl radicals were generated by photoinduced electron transfer (PET) from a suitable donor to the neophyl iodide (1, 1-iodo-2-methyl-2-phenylpropane). The PET reaction of 1 with the enolate anion of cyclohexenone (2) afforded mainly the reduction products tert-butylbenzene (5) and the rearranged isobutylbenzene (6), arising from hydrogen abstraction of the neophyl radical (15) and the rearranged radical 16 intermediates, respectively. The photostimulated reaction of 1 with 2 in the presence of di-tert-butylnitroxide, as a radical trap, afforded adduct 10 in 57% yield. The photoinduced reaction of the enolate anion of acetophenone (3) with 1 gave the substitution products 11 (50%) and 12 (16%), which arise from the coupling of 3 with radicals 15 and 16, respectively. The rate constant obtained for the addition of anion 3 to radical 15 was 1.2 × 105 M-1 s-1, by the use of the rearrangement of this radical as a clock reaction. The anion of nitromethane (4) was almost unreactive at the initiation step, but in the presence of 2 under irradiation, it gave high yields (67%) of the substitution product 13 and only 2% of the rearranged product 14. When the ratio of 4 to 1 was diminished, it was possible to observe both substitution products 13 and 14 in 16% and 6.4% yields, respectively. These last results allowed us to estimate the coupling rate constant of neophyl radicals 15 with anion 4 to be at least of the order of 106 M-1 s-1. Although the overall quantum yield determined (λ = 350 nm) for the studied reactions is below 1, the chain lengths (Φpropagation) for the reaction of 1 with anions 3 and 4 are 127 and 2, respectively.
- Argueello, Juan E.,Penenory, Alicia B.,Rossi, Roberto A.
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p. 7175 - 7182
(2007/10/03)
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- The kinetics and mechanisms of gas phase elimination of primary, secondary, and tertiary 2-hydroxyalkylbenzenes
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2-Phenylethanol, racemic l-phenyI-2-propanol, and 2-methyl-l-phenyl-2-propanol have been pyrolyzed in a static system over the temperature range 449.3-490.6oC and pressure range 65-198 torr. The decomposition reactions of these alcohols in seasoned vessels are homogeneous, unimolecular, and follow a first-order rate law. The Arrhenius equations for the overall decomposition and partial rates of products formation were found as follows: for 2-phenylethanol. overall rate log fe,(s-1) = 12.43 - 228.1 kj moM (2.303 /?T)-', toluene formation log fc,(s-1) = 12.97 - 249.2 kl moM (2.303 OT)-1. styrene formation log fe|(s~') = 12.40 - 229.2 kJ mol-1(2.303 R7}-1. ethylbenzene formation log fe,(s-1) = 12.96 - 253.2 k| mol-'(2.303 RT)-1; for l-phenyl-2-propanol, overall rate log fe,(s-1) = 13.03 - 233.5 k| mol-'(2.303 RT)-1. toluene formation log fc,(s-1) = 13.04 - 240.1 kJ mol-1(2.303 RT)-1, unsaturated hydrocarbons + indene formation logfe,(s-1) = 12.19 - 224.3 kj mol-1(2.303 RT)-1;for 2-methyl-l-phenyl-2-propanol, overall rate log fe,(s-1) = 12.68 - 222.1 kJ mol-1(2.303 RT-1l. toluene formation log fe,(s-1) = 12.65 - 222.9 kj mol-1(2.303 RT)-]. phenylpropenes formation log fe1(s-1) = 12.27 - 226.2 k) mol-1(2.303 RT)-1. The overall decomposition rates of the 2-hydroxyalkylbenzenes show a small but significant increase from primary to tertiary alcohol reactant. Two competitive eliminations are shown by each of the substrates: the dehydration process tends to decrease in relative importance from the primary to the tertiary alcohol substrate, while toluene formation increases. 1999 lohn Wiley & Sons, Inc.
- Chuchani, Gabriel,Rotinov, Alexandra,Dominguez, Rosa M.
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p. 401 - 407
(2007/10/03)
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- The Palladium-Catalyzed Cross-Coupling Reaction of Organosilicon Compounds with Allylic Carbonates or Diene Monoxides
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The cross-coupling reaction of allylic carbonates with organosilanes was found to proceed without fluoride ion activation under mild conditions by using a coordinatively unsaturated palladium complex as a catalyst.The reaction was assumed to proceed through an allylpalladium alkoxide derived from the allylic carbonate substrate and a palladium(0) species, the alkoxo ligand activating the organosilicon reagent.Likewise, diene monoxides also underwent cross-coupling with alkenyl- and arylfluorosilanes in moderate to high yields.
- Matsuhashi, Hayao,Asai, Satoshi,Hirabayashi, Kazunori,Hatanaka, Yasuo,Mori, Atsunori,Hiyama, Tamejiro
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p. 1943 - 1952
(2007/10/03)
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- Photolysis of Alkyl Aryl Sulfoxides: α-Cleavage, Hydrogen Abstraction, and Racemization
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The photochemistry of a series of alkyl aryl sulfoxides is described. The initial event of the photolysis process is homolytic cleavage to form sulfinyl/alkyl radical pairs. The radical pair partitions between recombination to starting material, formation of sulfenic esters, disproportionation to an olefin and benzenesulfenic acid, and formation of typical radical escape products. The quantum yield for conversion depends on the structure or the reactivity of the alkyl radical, with the sequence benzyl > tertiary alkyl > secondary alkyl > primary alkyl > (di)aryl. The high racemization efficiency of some aryl primary-alkyl sulfoxides suggests that another nonradical pathway for the photoracemization process may exist. Product analysis does not support any hydrogen abstraction pathways.
- Guo, Yushen,Jenks, William S.
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p. 857 - 864
(2007/10/03)
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- Synthesis of 4,4-disubstituted β-lactams by regiospecific electrophile- and silver-induced ring expansion of 2,2-disubstituted 1-methoxycyclopropylamines
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2,2-Disubstituted 1-methoxycyclopropylamines underwent regiospecific ring expansion to 1,4,4-trisubstituted 2-azetidinones by N-chlorination with tert-butyl hypochlorite and subsequent rearrangement with silver tetrafluoroborate. Upon thermolysis, 4,4-disubstituted β-lactams suffer a characteristic ring opening to afford β,γ-unsaturated carboxylic amides. The reduction of 1,4,4-trisubstituted 2-azetidinones with lithium aluminum hydride afforded 1,2,2-trisubstituted azetidines.
- De Kimpe, Norbert,Tehrani, Kourosch Abbaspour,Fonck, Gwendolien
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p. 6500 - 6503
(2007/10/03)
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- Formation of symmetrical alkenes by homocoupling of metallated sulfones under nickel catalysis
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Summary -Allylic sulfones undergo a coupling reaction with organometallic compounds (Mg or Li) not only with copper catalysts but also with iron or nickel salts. With 7,7-disubstituted allylic sulfones and also saturated aliphatic sulfones, however, another reaction was observed whereby two molecules of the starting sulfone are coupled to give symmetrical alkenes. The scope of this reaction was investigated. Elsevier.
- Gai, Yonghua,Julia, Marc,Jean-Noe,Verpeaux
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p. 805 - 816
(2007/10/03)
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- Trithioorthoesters and Tetrathioorthocarbonates as RC(3+) and C(4+) Synthons. Nickel-Catalyzed Alkylative Olefination of Trithioorthoesters and Tetrathioorthocarbonates
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NiCl2(PPh3)2-catalyzed alkylative olefinations of trithioorthoesters and tetrathioorthocarbonates give the corresponding substituted alkenes.Aliphatic C-S bonds in these substrates can be activated in the nickel-catalyzed cross coupling reaction leading to carbon-carbon bond formation.This reaction can be considered as using trithiorthoesters and tetrathioorthocarbonate as R3C(3+) and C(4+) synthons. - Keywords: Trithioorthoesters, Tetrathioorthocarbonate, Nickel-Catalyzed Alkylative Olefination, Synthons of RC(3+) and C(4+)
- Tzeng, Yih-Ling,Cheng, Wen-Lung,Luh, Tien-Yau
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p. 385 - 393
(2007/10/02)
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- Phenyl Migration in the Molecular Pyrolytic Elimination of 1-Chloro-2-methyl-2-phenylpropane in the Gas Phase
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The elimination of kinetics of 1-chloro-2-methyl-2-phenylpropane (neophyl chloride) in the gas phase were examined over a temperature range of 420-475 deg C and a pressure range of 34-134 Torr.The reaction, in seasoned static vessels and in the presence of a free radical suppressor, is molecular in nature and follows a first-order rate law.The Arrhenius equation for the elimination was found to be: log(k1/s-1)=(13.47+/-0.62) - (227.8+/-8.7) kJ mol-1 (2.303RT)-1.A Wagner-Meerwein phenyl migration was the prevailing pathway in the rearrangement process.This work provides strong evidence for an intimate ion-pair type of mechanism.
- Chuchani, Gabriel,Dominguez, Rosa M.
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p. 1499 - 1502
(2007/10/02)
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- One-Step Deoxygenation of Alcohols into Alkanes by a 'Double Electrolysis' in the Presence of a Phosphine
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Deoxygenation of primary and secondary alcohols was effectively achieved in one-step by constant current electrolysis of a mixture of a phosphine, an alcohol, and Et4NBr in CH3CN with one compartment cell at room temperature under N2 atmosphere.
- Maeda, Hatsuo,Maki, Toshihide,Eguchi, Kaoru,Koide, Takashi,Ohmori, Hidenobu
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p. 4129 - 4132
(2007/10/02)
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- Single insertion of α-olefins into the cationic complex [Zr(CH2Ph)3]+ affording isolable [Zr(CH2Ph)2(CH2CHRCH2Ph)] + adducts: A model for the insertion mechanism in ziegler-Natta polymerization
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The zwitterionic complex [Zr(CH2Ph)3{(η6-PhCH2)B(C 6F5)3}] (1) reacts smoothly at 25°C with propene and higher α-olefins, such as 4-methyl-1-pentene, 1-vinylcyclohexane, and allylbenzene, affording the single-insertion adducts [Zr(CH2Ph)2(CH2CHRCH2Ph)] +[B(CH2-Ph)(C6F5)3] - (R = Me, 2; R = CH2CHMe2, 4; R = C6H11, 5; R = CH2Ph, 6). Isolation and characterization of 2, 4, and 6 by NMR analysis reveal that the Zr cation is stabilized toward either further monomer insertion or β-hydrogen elimination by back-biting ηn-coordination of the δ-Ph ring and by η2-coordination of the two benzyl ligands. An analogous, less stable adduct deriving from single insertion of ethene (R = H, 3) has been detected at low temperatures by NMR. Thermolysis of 2 at 50°C, as well as addition of Lewis bases such as tetrahydrofuran, results in decomposition via β-hydrogen elimination with formation of CH2=CMeCH2Ph. At 50°C, 2 reacts with an excess of propene affording a mixture of atactic and isotactic polypropylene, probably after β-hydrogen elimination has occurred. In contrast, reaction of 2 with ethene proceeds already at 25°C, affording polyethylene, possibly through further insertion in 2. Compounds 2-6 are the first examples of adducts deriving from the insertion of olefins into the M-C bond of a group 4 metal complex which is an active Ziegler-Natta catalyst.
- Pellecchia, Claudio,Grassi, Alfonso,Zambelli, Adolfo
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p. 298 - 302
(2008/10/08)
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- Palladium Complexes Containing Rigid Bidentate Nitrogen Ligands as Catalysts for Carbon-Carbon Bond Formation
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Zerovalent Pd(Ar-BIAN)(dimethyl fumarate) and divalent PdCl2(Ar-BIAN) complexes containing the rigid bidentate nitrogen ligand bis(arylimino)acenaphthene (Ar-BIAN; Ar = C6H5, p-MeC6H4, p-MeOC6H4) are efficient catalysts for the cross coupling reaction of various organic halides (including acyl-, allyl-, aryl-, benzyl-, vinyl- and 1,2-dienylhalides) with organomagnesium, -zinc and -tin reagents.Coupling reactions of organic halides with one equivalent of organomagnesium and -zinc reagents, in the presence of 1 mol percent of a Pd(Ar-BIAN) catalyst, generally proceed smoothly in THF at 20 degC, giving complete conversion of the starting halide within 1-16 hours.Good isolated yields of carbon-carbon coupled products are obtained and the ratio cross/homo coupling varies between 98/2 and 0/100, depending on the substrates used.Reactions employing organotin reagents proceed best in DMF or HMPA and need longer reaction times and/or higher temperatures, as compared to organomagnesium and -zinc reagents, to go to completion.The selectivity for cross coupling is high (generally >99 percent) and high isolated yields of cross coupled products can be obtained.In the presence of carbon monoxide (1-5 bar) ketones can be formed with excellent selectivity and in good yields, as was demonstrated for the carbonylative coupling of benzyl bromide with tetramethyltin or (p-tolyl)trimethyltin.Comparison of some Pd(Ar-BIAN) catalyzed reactions with Pd-phosphine catalyzed reactions reveals that these reactions complement each other: for example, when a Pd(Ar-BIAN) catalyst was employed, the coupling of 2-methylallyl chloride with phenyltributyltin was much faster, whereas the coupling of iodobenzene with vinyltrimethyltin was much slower, as compared to the Pd(PPh3)n catalyzed reactions.
- Asselt, Rob van,Elsevier, Cornelis J.
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p. 323 - 334
(2007/10/02)
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- Direct Conversion of Alcohols into Thiols
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A simple one-pot reaction between alcohols and 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide (Lawesson's reagent, LR) affords the corresponding thiols, accompanied by dehydration products, alkenes.Treatment of acyclic 1,4-diols with LR gives the 1,3-dienes. o-(Dihydroxymethyl)benzene derivatives yield the 1,3-dihydrobenzothiophenes when treated with LR.
- Nishio, Takehiko
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p. 1113 - 1118
(2007/10/02)
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