- Three-step synthetic pathway to fused bicyclic hydantoins involving a selenocyclization step
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Sequential 5-alkenyl hydantoin and pyrrolidine ring-forming reactions have been applied in the synthesis of conformationally constrained fused bicyclic scaffold. They are assembled by a three-step reaction sequence from two variable building blocks (readily available β-ketoesters and alkenyl halides) by combining a Bucherer-Bergs reaction with a final selenium-promoted intramolecular cyclization as a key step. The chemoselectivity of this bicyclic hydantoin formation is strongly influenced by experimental factors such as the solvent and the use of additives. The reaction is regiospecific giving only five-membered fused bicyclic hydantoins in good to excellent yields stemming from the nucleophilic attack of the nitrogen atom to a cyclic seleniranium ion intermediate during the cyclization step. A separable diastereomeric mixture is obtained; the products with bridgehead substituents and phenylseleno groups in cis relationships were formed predominantly. The reaction tolerates a variety of substitution at the double bond, furthermore, the presence of substituents at C(5) and N(3) position opens up the capability of generating a broad structural diversity.
- ?mit, Biljana M.,Pavlovi?, Radoslav Z.
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- FREE RADICAL CHAIN REACTION OF ALLYLIC TIN COMPOUNDS WITH ORGANIC HALIDES INVOLVING SH prime PROCESS.
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Negatively substituted halomethanes were allylated easily by allyltin compounds via radical chain reaction involving S//H prime process. Aryl, aralkyl, and alkyl halides underwent similar chain reactions only when the tin compound was charged in excessive amounts.
- Migita,Nagai,Kosugi
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Read Online
- Kinetic resolution of racemic secondary alcohols via oxidation with Yarrowia lipolytica strains
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Cyclic and alicyclic racemic secondary alcohols are kinetically resolved via oxidation with Yarrowia lipolytica strains. The comparison of the oxidation reactions with the reductions of the corresponding ketones supports the hypothesis of the presence of
- Fantin, Giancarlo,Fogagnolo, Marco,Medici, Alessandro,Pedrini, Paola,Fontana, Silvia
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- Atroposelective Synthesis of Axially Chiral N-Arylpyrroles by Chiral-at-Rhodium Catalysis
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A transformation of fluxional into configurationally stable axially chiral N-arylpyrroles was achieved with a highly atroposelective electrophilic aromatic substitution catalyzed by a chiral-at-metal rhodium Lewis acid. Specifically, N-arylpyrroles were alkylated with N-acryloyl-1H-pyrazole electrophiles in up to 93 percent yield and with up to >99.5 percent ee, and follow-up conversions reveal the synthetic utility of this new method. DFT calculations elucidate the origins of the observed excellent atroposelectivity.
- Chen, Shuming,Han, Feng,Houk, K. N.,Ivlev, Sergei,Meggers, Eric,Xie, Xiulan,Ye, Chen-Xi
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- Erbium(III) triflate: A valuable catalyst for the rearrangement of epoxides to aldehydes and ketones
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Rearrangement of epoxides is performed with erbium triflate as catalyst. In contrast to most proposed catalysts for this re-action, erbium triflate works well with both aromatic and aliphatic epoxides.
- Procopio, Antonio,Dalpozzo, Renato,De Nino, Antonio,Nardi, Monica,Sindona, Giovanni,Tagarelli, Antonio
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- Polyethylene-Bound Soluble Recoverable Palladium(0) Catalysts
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The use of diphenylphosphine-terminated ethylene oligomers as ligands for palladium(0) and palladium(II) is described.With use of these polymeric ligands, it is possible to carry out homogeneous reactions characteristic of (Ph3P)4Pd and (Ph3P)2Pd(OAc)2 with essentially complete recovery of the Pd catalyst.The only limitation to repeated reuse of the catalyst is its immolative catalytic oxidation of the phosphine ligand by adventitious oxygen.
- Bergbreiter, David E.,Weatherford, David A.
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- PALLADIUM-CATALYZED REARRANGEMENT OF ALLYLIC ESTERS OF ACETOACETIC ACID TO GIVE γ,δ-UNSATURATED METHYL KETONES
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Various allylic esters of acetoacetic acid undergo rearrangement to give γ,δ-unsaturated methyl ketones in high yields with elimination of carbon dioxide under mild conditions in the presence of catalytic amounts of Pd(OAc)2 and PPh3.
- Shimizu, Isao,Yamada, Toshiro,Tsuji, Jiro
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- A NOVEL SYNTHESIS OF TERMINAL OLEFINS BY ANODIC OXIDATION OF CARBOXYLIC ACIDS HAVING A TRIMETHYLSILYL GROUP ON THE β-POSITION
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Anodic oxidation of carboxylic acids having a trimethylsilyl group on the β-position gave exclusively terminal olefins in reasonable yields.
- Shono, Tatsuya,Ohmizu, Hiroshi,Kise, Naoki
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- Conversion of ketoximes to ketones with trimethylphosphine and 2,2′-dipyridyl diselenide
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Use of trimethylphosphine (Me3P) and 2,2′-dipyridyl diselenide (PySeSePy) is an excellent method for the conversion of ketoximes to the corresponding ketones, since yields higher than 90% are obtained at rt within a fewminutes (or hours for the more reluctant substrates, which do not react with Bu3P/PhSSPh). In the simplest cases, the reaction can be completed with 30mol% of PySeSePy, provided that an excess of phosphine is present in the reaction medium.
- Martín, Manuel,Martínez, Gabriel,Urpí, Fèlix,Vilarrasa, Jaume
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Read Online
- An efficient method for deprotection of acetals
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A variety of acetonides and acetals were efficiently cleaved using CuCl2.2H2O in MeCN. The method was effectively used in synthesis of chiral diols which are important in asymmetric synthesis.
- Saravanan,Chandrasekhar,Anand, R. Vijaya,Singh, Vinod K.
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Read Online
- Chromium-Catalyzed Production of Diols From Olefins
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Processes for converting an olefin reactant into a diol compound are disclosed, and these processes include the steps of contacting the olefin reactant and a supported chromium catalyst comprising chromium in a hexavalent oxidation state to reduce at least a portion of the supported chromium catalyst to form a reduced chromium catalyst, and hydrolyzing the reduced chromium catalyst to form a reaction product comprising the diol compound. While being contacted, the olefin reactant and the supported chromium catalyst can be irradiated with a light beam at a wavelength in the UV-visible spectrum. Optionally, these processes can further comprise a step of calcining at least a portion of the reduced chromium catalyst to regenerate the supported chromium catalyst.
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Paragraph 0111
(2021/03/19)
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- Iron-catalyzed carbonylative cyclization of γ,δ-unsaturated aromatic oxime esters to functionalized pyrrolines
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Herein, a new method of iron-catalyzed carbonylative cyclization of γ,δ-unsaturated aromatic oxime esters to functionalized pyrrolines has been developed. By using readily available substrates, 32 examples of functionalized pyrrolines were prepared in moderate to good yields. Notably, examples of reduction and cycloaddition reactions of the obtained product were given as well. This journal is
- Wang, Hai,Wu, Xiao-Feng,Yin, Zhiping,Zhang, Youcan
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supporting information
p. 7045 - 7048
(2020/07/14)
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- Synthesis of a Water-Soluble Ruthenium Complex and Its Catalytic Activity for Acceptorless Alcohol Dehydrogenation in Aqueous Medium
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The synthesis of a ruthenium complex bearing a PN-chelating ligand is described. The complex, in the presence of KOH, enabled the synthesis of ketones from secondary alcohols in the absence of a hydrogen acceptor in aqueous medium. This synthetic protocol, which uses water as the medium, is green and has a high atom economy as it avoids the use of an acceptor and produces hydrogen as the sole byproduct. Mechanistic investigations revealed that the catalytic cycle involves a phosphine dissociative pathway.
- Bhatia, Anita,Muthaiah, Senthilkumar
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supporting information
p. 1644 - 1648
(2018/06/26)
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- Oximinotrifluoromethylation of unactivated alkenes under ambient conditions
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An efficient protocol for oximinotrifluoromethylation of unactivated alkenes was developed via trifluoromethyl radical-induced intramolecular remote oximino migration under mild reaction conditions, providing a wide range of β-trifluoromethylated oximes. Other fluoroalkyl radicals were also applicable for this transformation. This method provided access to synthetically challenging medium-sized ring scaffolds and the 6,7,5-fused lactam skeleton.
- Wang, Na,Wang, Jian,Guo, Yu-Long,Li, Lei,Sun, Yan,Li, Zhuang,Zhang, Hong-Xia,Guo, Zhen,Li, Zhong-Liang,Liu, Xin-Yuan
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supporting information
p. 8885 - 8888
(2018/08/17)
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- Atom-economical cobalt-catalysed regioselective coupling of epoxides and aziridines with alkenes
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We demonstrate that a simple cobalt complex can regioselectively couple epoxides and aziridines with alkenes to generate valuable homoallylic alcohols and amines. The intramolecular reaction exhibits complete atom economy and, in contrast to traditional Mizoroki-Heck reactions, does not require stoichiometric amounts of base. An indole derivative was also shown to be a suitable coupling partner. Finally, promising results regarding the development of an intermolecular process using both epoxides and aziridines are reported, as well as preliminary mechanistic studies suggesting a radical mechanism.
- Prina Cerai, Gabriele,Morandi, Bill
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supporting information
p. 9769 - 9772
(2016/08/04)
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- Studies on the low-temp oxidation of coal containing organic sulfur and the corresponding model compounds
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This paper selects two typical compounds containing organic sulfur as model compounds. Then, by analyzing the chromatograms of gaseous low-temp oxidation products and GC/MS of the extractable matter of the oxidation residue, we summarizing the mechanism of low-temp sulfur model compound oxidation. The results show that between 30 °C to 80 °C, the interaction between diphenyl sulfide and oxygen is mainly one of physical adsorption. After 80 °C, chemical adsorption and chemical reactions begin. The main reaction mechanism in the low-temp oxidation of the model compound diphenyl sulfide is diphenyl sulfide generates diphenyl sulfoxide, and then this sulfoxide is further oxidized to diphenyl sulphone. A small amount of free radicals is generated in the process. The model compound cysteine behaves differently from diphenyl sulfide. The main reaction low-temp oxidation mechanism involves the thiol being oxidized into a disulphide and finally evolving to sulfonic acid, along with SO2 being released at 130 °C and also a small amount of free radicals. We also conducted an experiment on coal from Xingcheng using X-ray photoelectron spectroscopy (XPS). The results show that the major forms of organic sulfur in the original coal sample are thiophene and sulfone. Therefore, it can be inferred that there is none or little mercaptan and thiophenol in the original coal. After low-temp oxidation, the form of organic sulfur changes. The sulfide sulfur is oxidized to the sulfoxide, and then the sulfoxide is further oxidized to a sulfone, and these steps can be easily carried out under experimental conditions. What's more, the results illustrate that oxidation promotes sulfur element enrichment on the surface of coal.
- Zhang, Lanjun,Li, Zenghua,Li, Jinhu,Zhou, Yinbo,Yang, Yongliang,Tang, Yibo,McPhee, Derek J.
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p. 22241 - 22256
(2016/01/25)
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- Z -selective ethenolysis with a ruthenium metathesis catalyst: Experiment and theory
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The Z-selective ethenolysis activity of chelated ruthenium metathesis catalysts was investigated with experiment and theory. A five-membered chelated catalyst that was successfully employed in Z-selective cross metathesis reactions has now been found to be highly active for Z-selective ethenolysis at low ethylene pressures, while tolerating a wide variety of functional groups. This phenomenon also affects its activity in cross metathesis reactions and prohibits crossover reactions of internal olefins via trisubstituted ruthenacyclobutane intermediates. In contrast, a related catalyst containing a six-membered chelated architecture is not active for ethenolysis and seems to react through different pathways more reminiscent of previous generations of ruthenium catalysts. Computational investigations of the effects of substitution on relevant transition states and ruthenacyclobutane intermediates revealed that the differences of activities are attributed to the steric repulsions of the anionic ligand with the chelating groups.
- Miyazaki, Hiroshi,Herbert, Myles B.,Liu, Peng,Dong, Xiaofei,Xu, Xiufang,Keitz, Benjamin K.,Ung, Thay,Mkrtumyan, Garik,Houk,Grubbs, Robert H.
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supporting information
p. 5848 - 5858
(2013/05/22)
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- Oxidant-free lactonization of diols using a hydrotalcite-supported copper catalyst
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We newly synthesized well-crystallized hydrotalcite-supported copper nanoparticles, denoted as Cu/HT(c), which acted as a highly efficient heterogeneous catalyst for oxidant-free lactonization of various diols under liquid-phase conditions. The Cu/HT(c) catalyst could be recovered by simple filtration and reused without the significant loss of its activity and selectivity.
- Mikami, Yusuke,Ebata, Kaori,Mitsudome, Takato,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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experimental part
p. 855 - 861
(2010/09/16)
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- New, general, and practical preparation of methyl ketones via the direct coupling of amides with CH2CI2 promoted by TiCI 4/Mg
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The direct coupling of a variety of amides with CH2CI 2 or CD2CI2 promoted by TiCI4/Mg/THF provides an extremely simple, practical, selective, and efficient approach for the construction of methyl ketones. The efficiency and practicability of this chemistry is illustrated by the very simple synthesis of deuterated methyl ketones.
- Lin, Kuo-Wei,Tsai, Chi-Hui,Hsieh, L-Lin,Yan, Tu-Hsin
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supporting information; experimental part
p. 1927 - 1930
(2009/04/10)
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- Dioxime oxalates; new iminyl radical precursors for syntheses of N-heterocycles
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Symmetrical and unsymmetrical dioxime oxalates were prepared by treatment of oximes with oxalyl chloride. UV photolysis of these precursors was found to be an atom-efficient way of generating iminyl radicals. The process was most efficient for dioxime oxalates having aryl substituents attached to their C{double bond, long}N bonds. The method was useful for EPR spectroscopic study of iminyl and iminoxyl radicals. Photolyses in toluene solution, of dioxime oxalates containing alkenyl acceptor groups, yielded unsaturated iminyl radicals that ring closed to afford 3,4-dihydro-2H-pyrroles in good yields. Dioxime oxalates with biphenyl substituents also released iminyl radicals that ring closed onto the aromatic acceptor groups and, in acetonitrile solution, this approach provided a useful and atom-efficient method of making substituted phenanthridines.
- Portela-Cubillo, Fernando,Lymer, James,Scanlan, Eoin M.,Scott, Jackie S.,Walton, John C.
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supporting information; experimental part
p. 11908 - 11916
(2009/04/06)
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- Reactions of diazoalkanes with unsaturated compounds 16. Catalytic reactions of diazomethane with 2-alkenyl-1,3-oxazolidines and 2-alkenyl-1,3-oxathiolanes
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The influence of 1,3-oxazolidine and 1,3-oxathiolane fragments in substituted alkenes on the direction of their catalytic reaction with diazomethane has been investigated. The olefins bearing an oxazolidine substituent in the α- or γ-position and an oxathiolane substituent in the γ-position relative to the C=C bond react with diazomethane in the presence of Pd(acac)2 selectively resulting in cyclopropanation products. The use of Cu(OTf)2 does not result in cyclopropanation; however Cu(OTf)2 catalyzes the reaction of diazomethane with 2-(alk-1-enyl)-1,3-oxathiolanes yielding 2,3,5,6-tetrahydro-1,4-oxathiocines formed through the [2,3]-sigmatropic rearrangement of the intermediate sulfonium ylides.
- Khanova,Sultanova,Rafikov,Baykova,Biglova,Dokichev,Tomilov, Yu. V.
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experimental part
p. 617 - 621
(2009/05/15)
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- Low pressure carbonylation of heterocycles
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Heterocycles, e.g., epoxides, are carbonylated at low pressure with high percentage conversion to cyclic, ring expanded products using the catalyst where L is tetrahydrofuran (THF).
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Page/Page column 4
(2008/06/13)
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- A cross-metathesis route to functionalized α-methyl α-substituted amino acids
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A chemoenzymatic approach to the synthesis of functionalized α-methyl α-substituted amino acids is detailed. This involves amidasemediated enzymatic resolution of α-methyl α-substituted side-chain ω-unsaturated amino acids followed by functionalization via cross-metathesis.
- Storcken, Roy P. M.,Panella, Lavinia,Van Delft, Floris L.,Kaptein, Bernard,Broxterman, Quirinus B.,Schoemaker, Hans E.,Rutjes, Floris P. J. T.
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p. 161 - 164
(2008/02/03)
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- Stereoselective synthesis of the monomeric unit of SCH 351448
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The monomeric unit of the macrodiolide SCH 351448 has been synthesized from three building blocks. Strategic disconnections were chosen between C21-C22 (Wittig) and C10-C11 (stereoselective aldol). The cis configuration of both 2,6-disubstituted tetrahydropyran rings was established by a stereoselective cationic reduction. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Backes, J. Rene,Koert, Ulrich
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p. 2777 - 2785
(2007/10/03)
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- Practical β-lactone synthesis: Epoxide carbonylation at 1 atm
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A readily prepared bimetallic catalyst is capable of effecting epoxide carbonylation to produce β-lactones at substantially lower CO pressures than previously reported catalyst systems. A functionally diverse array of β-lactones is produced in excellent yields at CO pressures as low as 1 atm. This procedure allows for epoxide carbonylation on a multigram scale without the requirement of specialized, high-pressure equipment.
- Kramer, John W.,Lobkovsky, Emil B.,Coates, Geoffrey W.
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p. 3709 - 3712
(2007/10/03)
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- Rhenium-Catalyzed Epoxide Deoxygenation: Scope and Limitations
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Transfer of oxygen atoms from epoxides to triphenylphosphine is efficiently catalyzed by Tp′ReO3 [Tp′ = hydrido-tris-(3,5-dimethylpyrazolyl)borate] in benzene at 75-105 °C. The reaction tolerates a wide variety of functional groups including ketones (conjugated or non-conjugated to the new double bond), esters, nitriles, ethers, silyl ethers and phthalimides. Relative rates vary with substitution pattern and electronics; in general, monosubstituted and 2,2-disubstituted epoxides react fastest, and cis-2,3-disubstituted systems react faster than trans. Electron-withdrawing substituents promote the reaction.
- Gable, Kevin P.,Brown, Eric C.
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p. 2243 - 2245
(2007/10/03)
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- Oxidative addition of allylic substrates to coordinatively unsaturated ruthenium compounds, [Ru(η5-C5Me5)(η-amidinate)]: Preparation, structure elucidation, and catalysis of novel ruthenium (IV)-η3-allyl complexes
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Oxidative addition reactions of allylic halides, acetates, and carbonates with [Ru(η5-C5Me5)(η-amidinate)] [amidinate: iPrNC(Me)=NiPr (1a), 1BuNC(Ph)=N1Bu (1b)], which shows signs of coordinative unsaturation, gave novel cationic π-allyl ruthenium(IV) species. The compounds [Ru(η3-allyl)(η5-C5Mes)(η 2-amidinate)]+X- were isolated by anion exchange of the products (X = PF6, BF4, BPh4), and were characterized by spectroscopic analysis. The crystallography of two of the [Ru(η3-allyl)(η5-C5Mes)(η 2-amidinate)] +X- revealed a four-legged piano stool structure in which two nitrogen atoms in the amidinate ligand and two carbon atoms in the η3-allyl ligands occupy the positions of four legs; the orientation of the η3-allyl ligand was endo. Although cyclic voltammograms of the precursor, [Ru(η5-C5Me5)(η-amidinate)], indicated possible oxidative addition of organic halides other than allylic halides to [Ru(η5-C5Me5)(η-amidinate)], only allylic halides gave the corresponding Ru(IV) products. The importance of prior coordination of the carbon-carbon double bond of allylic substrates was evidenced by NMR observation of the intermediate in the reaction of 1a or 1b with allyl acetate. Addition of nucleophiles such as PhLi, dimethyl methylsodiomalonate, and piperidine to the [Ru(η3-allyl)(η5-C5Me 5)(η2-amidinate)]+X- gave rise to allylation of these nucleophiles and regeneration of [Ru(η5-C5Me5)(η-amidinate)]. The reactions of allyl methyl carbonate with nucleophiles were also achieved by catalysis of either [Ru(η5C5Me5)(η-amidinate)] or [Ru(η3-allyl)(η5-C5Me 5)(η2-amidinate)]+X-.
- Kondo, Hideo,Kageyama, Akira,Yamaguchi, Yoshitaka,Haga, Masa-Aki,Kirchner, Karl,Nagashima, Hideo
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p. 1927 - 1937
(2007/10/03)
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- Synthesis of functional monomers based on β-diketones
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Unsaturated β-diketones - 3-allylpentane-2,4-dione, 3-allyl-1,1,1-trifluoropentane-2,4-dione, and 2-allyl-1-phenylbutane-1,3-dione-were prepared by two independent procedures: condensation and alkylation. The compounds were characterized by elemental analysis and 1H NMR and IR spectroscopy. The copper, nickel, and cobalt complexes of these β-diketones were prepared, and their thermal behavior was examined.
- Voloshanovskii,Manaeva,Shevchenko,Mamontov
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p. 296 - 300
(2007/10/03)
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- Radical addition to carbenoids. Chain reactions of α-diazo carbonyl compounds with triorganotin hydrides, tris(trimethylsilyl)silane and allyltributylstannane
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α-Diazo ketones RC(O)CH=N2 react with tributyltin hydride at 60°C in benzene to give the corresponding α-stannyl ketones RC(O)CH2SnBu3, which exist in equilibrium with the stannyl enol ether tautomers R(Bu3SnO)C=CH2. The reactions are initiated by di-tert-butyl hyponitrite and follow a free-radical chain mechanism. Triphenyltin hydride and tris(trimethylsilyl)silane [(TMS)3SiH] react similarly, the latter to yield the α-silyl ketone RC(O)CH2Si(TMS)3 which does not isomerise to the more stable silyl enol ether R[(TMS)3SiO]C=CH2 under the reaction conditions. This result indicates that TMS3Si. reacts at the α-carbon atom of the α-diazo ketone to give R(CO)CHSiTMS3, probably via an initial diazenyl radical adduct; triorganotin radicals are assumed to react in the same way. When the group R in the α-diazo ketone is but-3-enyl, the intermediate α-metalloalkyl radical undergoes 5-exo-cyclisation. Allyltributylstannane reacts with α-diazo ketones and with ethyl α-diazoacetate in refluxing benzene, in the presence of 2,2′-azo(2-methylpropionitrile) as initiator, to give butenyl ketones RC(O)CH2CH2CH=CH2 and ethyl pent-4-enoate, respectively, after a hydrolytic work-up.
- Dang, Hai-Shan,Roberts, Brian P.
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p. 769 - 775
(2007/10/03)
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- REACTION OF HOMOALLYLIC COMPOUNDS OF TIN WITH ACYLATING AGENTS
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In the reaction of homoallylic organotin compounds with carboxylic acid anhydrides and chlorides in the presence of Lewis acids cyclopropyl methyl ketones are formed with α,β-unsaturated ketones and β-chloro ketones as impurities.The ratio of the reaction products depends on the temperature, the structure of the reagents, and the type of catalyst.
- Ivashchenko, N. B.,Polunin, E. V.,Kashin, A. N.
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p. 546 - 550
(2007/10/02)
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- Photoinduced Electron Transfer (PET) Promoted Cross-coupling of Organoselenium and Organosilicon Compounds: a New Carbon-Carbon Bond Formation Strategy
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PET promoted cross-coupling of organoselenium compounds and silyl enol ethers is reported.
- Pandey, Ganesh,Sochanchingwung, R.
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p. 1945 - 1946
(2007/10/02)
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- Steric effects in intramolecular [2+2] photocycloaddition of C=C double bonds to cyclohexenones
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The effect of substituents on the mode of approach and the endo/exo ratio in intramolecular [2+2] photocycloaddition reactions were studied.
- Becker,Haddad
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p. 947 - 964
(2007/10/02)
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- Oxidative Addition Reactions of ω-Alkenyl Nitronate Anions
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Anions are oxidatively added to nitronate anions to yield α-substituted nitroalkanes when potassium hexacyanoferrate(III) is used as oxidant.Oxidation of nitronate anions yields intermediate α-nitroalkyl radicals, which undergo addition by anions to give intermediate α-substituted nitroalkane radical anions, which are further oxidised to yield the α-substituted nitroalkanes.The nitronate anions used are derived from 5-nitrohex-1-ene, 6-nitrohept-1-ene, endo-5-nitro-exo-6-phenylbicyclohept-2-ene, and 1-(bicyclohept-5-en-endo-2-yl)-2-nitropropane.The intermediate α-nitroalkyl onto the ω-alkenes.The α-nitroalkyl radical derived from 1-(bicyclohept-5-en-endo-2-yl)-2-nitropropane underwent cyclisation when the oxidation was carried out in the absence of an added anion.The addition of anions (thiocyanate, benzenesulfinate, 4-chlorobenzenethiolate, and nitrite) to the α-nitroalkyl radicals derived from endo-5-nitro-exo-6-phenylbicyclohept-2-ene occurred stereoselectively from the less hindered exo face.Oxidative addition of 4-chlorobenzenethiolate to the nitronate from endo-5-nitro-exo-6-phenylbicyclohept-2-ene gave an unusual cyclisation via addition of a thiyl radical to the alkene.
- Bowman, W. Russell,Brown, David S.,Burns, Catherine A.,Crosby, David
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p. 2099 - 2106
(2007/10/02)
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- Oxymetallation. Part 24. Preparation of cyclic peroxides by cycloperoxymercuriation of unsaturated hydroperoxides
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Seventeen unsaturated hydroperoxides have been converted by treatment with mercury(II) acetate and/or mercury(II) nitrate into nineteen new mercuriated cyclic peroxides and by subsequent demercuriation with alkaline sodium borohydride, six new mercury-free peroxides have been isolated. The results greatly extend the range of such reactions and provide information about the stereoselectivities and relative ease of several different modes of cycloperoxymercuriation. It is suggested that the reactions with mercury(II) acetate are kinetically controlled whereas those with mercury(II) nitrate show a component of thermodynamic control of product distribution.
- Bloodworth,Curtis,Spencer,Tallant
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p. 2729 - 2750
(2007/10/02)
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- Reduction of Substituted Nitro Compounds with Tri-n-butyltin Hydride
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α-Substituted nitro compounds have been reduced with tri-n-butyltin hydride to give replacement of the α-substituent by hydrogen (2-bromo, 2-chloro- and 2-nitro-2-phenylsulphonylpropane to 2-nitropropane; p-nitrobenzyl chloride, bromide, iodide and thiocyanate to p-nitrotoluene; 5-nitrofurfuryl nitrate to 2-methyl-5-nitrofuran and 2-hydroxymethyl-5-nitrofuran; 2-(bromomethyl)-1-methyl-5-nitroimidazole to 1,2-dimethylimidazole). 2-Bromo-2-nitrohept-6-ene and 1-bromo-1-nitrohex-5-ene were reduced to 2-nitrohept-6-ene and 1-nitrohex-5-ene,5-bromo- and 5-phenylsulphonyl-5-nitro-6-phenyl-norborn-6-ene to 5-nitro-6-phenylnorborn-6-ene and 2-iodo-2-nitro-3-(endo-norborn-2-en-5-yl)propane to 2-nitro-3-(endo-norborn-2-en-5-yl)propane without cyclisation of the intermediate alkenyl α-nitroalkyl radicals. 2-Bromo-2-nitrohex-5-ene and 1-bromo-1-nitropent-4-ene were reduced to the respective nitroalkenes at high but at lower cyclisation to 1-methyl-1-nitrocyclopentane and 1-nitrocyclopentane took place.Inhibition studies of the reductions of 2-bromo-2-nitrohex-5-ene and p-nitrobenzyl bromide showed a radical chain mechanism.In some of the reductions at low , radical rearrangement of the intermediate α-nitroalkyl radicals gave the respective ketones.Mechanisms involving (a) addition/elimination and (b) dissociation of intermediate radical anions, are proposed.
- Bowman, W. Russell,Crosby, David,Westlake, Paul J.
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- Energetic and Rate Effects of the Trifluoromethyl Group at C-2 and C-4 on the Aliphatic Claisen Rearrangement
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The rate of the Claisen rearrangement is accelerated by a factor of 73 over the parent system when a trifluoromethyl group is present at C-2 of allyl vinyl ether.Ground-state destabilization by the trifluoromethyl group may be responsible for this rate effect.There is little polar character in the transition state, and the transition-state structure has little carbonyl character and only moderate (ca. 1/3) bonding character between the two terminal carbons.The rate enhancement is not observed in the Cope rearrangement of the all-carbon analogue that has a trifluoromet hyl group at C-2.At C-4, the trifluoromethyl group does not bring about a significant rate effect in the Claisen rearrangement relative to the parent system; this result is in contrast to an energetic benefit of 3.5 kcal/mol enjoyed by the system when a cyano group is at C-4, which suggests that radical-stabilizing ability and not electronic-withdrawing ability is important in stabilizing the transition state.
- Gajewski, J. J.,Gee, K. R.,Jurayj, J.
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p. 1813 - 1822
(2007/10/02)
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- AN EFFICIENT AND HIGHLY SELECTIVE METHOD FOR DEOXYMATION OF KETOXIMES
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A combination of pyridinium dichromate/tert-butyl hydroperoxide (1:1) has been found to be an excellent reagent for the highly selective regeneration of ketones from ketoximes.
- Chidambaram, N.,Satyanarayana, K.,Chandrasekaran, S.
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p. 1727 - 1734
(2007/10/02)
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- SELECTIVE OXIDATION OF ALCOHOLS BY MANGANATES
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K2MnO4 oxidized allylic and benzylic alcohols but did not affect saturated alcohols under phase-transfer catalysis condition, whereas a solid mixture of BaMnO4, Al2O3, and CuSO4*5H2O selectively oxidized allylic, benzylic, and saturated secondary hydroxy groups to the corresponding carbonyl groups in the presence of saturated primary hydroxy groups.
- Kim, Kwan Soo,Chung, Sangjae,Cho, In Haeng,Hahn, Chi Sun
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p. 2559 - 2562
(2007/10/02)
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- An Electron Spin Resonance Study of the Regioselectivity of the Cyclization of Protonated and Unprotonated Pent-4-en-1-oxyl and Pent-4-en-1-peroxyl Radicals
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The regioselectivity of the ring closure of protonated and unprotonated pent-4-en-1-oxyl radicals has been determined by monitoring by e.s.r. spectroscopy the radicals which are formed when the corresponding pent-4-enyl peroxides (2; R = H or Me) are photolysed in solution.Under neutral conditions, the spectra of the corresponding tetrahydrofuran-2-ylmethyl radicals (6) are observed, confirming the preferential 5-exo-mode of cyclization.When trifluoroacetic acid is present, the different spectra of the protonated tetrahydrofuran-2-ylmethyl radicals (8) are observed, and it is argued that this reflects the similar regioselectivity of the intramolecular addition of the protonated alkoxyl radicals.The identity of the radicals (6) and (8) was confirmed by generating them independently by abstracting bromine atoms from the corresponding bromides (9).Similar experiments with the hydroperoxides (1) failed to show the spectra of the dioxan-3-ylmethyl radicals (17), perhaps because they rapidly undergo γ-scission to the oxygen-centred radicals (18).However, (17) could be trapped with oxygen to afford, after Ph3P reduction, 1,2-dioxanes (4).No evidence could be found for the protonation of alkylperoxyl radicals by trifluoroacetic acid.
- Bloodworth, A. J.,Davies, Alwyn G.,Hay-Motherwell, Robyn S.
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p. 575 - 582
(2007/10/02)
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- PREPARATION OF THERMODINAMICALLY STABLE ENOL SILYL ETHERS OF γ,δ-UNSATURATED KETONES BY PALLADIUM-CATALYZED DECARBOXYLATION-ALLYLATION OF ALLYL 2,3-DISUBSTITUTED 3-TRIMETHYLSILOXYACRYLATES
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Allyl 2,3-disubstituted 3-trimethylsiloxyacrylates underwent palladium-catalyzed intramolecular decarboxylation-allylation to afford enol silyl ethers of γ,δ-unsaturated ketones.
- Tsuji, Jiro,Ohashi, Yukihiro,Minami, Ichiro
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p. 2397 - 2398
(2007/10/02)
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- Palladium-Catalyzed Decarboxylative Allylic Alkylation of Allylic Acetates with β-Keto Acids
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In the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium, β-keto acids react with allylic acetates at ambient temperature to produce α-allylic ketones in good yields with quantitative decarboxylation.This palladium-catalyzed decarboxylative allylic alkylation of allylic acetates with β-keto acids is characterized by high regio- and stereoselectivity.Allylation of β-keto acid takes place at the carbon atom bearing a carboxyl group.Allylic alkylation of allylic acetate with β-keto acid occurs at the less substituted end of the allyl group.The resultant carbon-carbon double bond of the α-allylic ketone has the E configuration.Allylic alkylation of lactone 25 with benzoylacetic acid proceeds preferably with retention of configuration, indicative of trans attack of the enolate on the (?-allyl)palladium intermediate from the opposite side of palladium even in the coexistence of free carboxylic acids.
- Tsuda, Tetsuo,Okada, Masahiro,Nishi, Sei-ichi,Saegusa, Takeo
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p. 421 - 426
(2007/10/02)
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- PALLADIUM(II)-CATALYZED CLAISEN REARRANGEMENT OF ALLYL VINYL ETHERS
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The Claisen rearrangement of allyl vinyl ethers is catalyzed by PdCl2(CH3CN)2, provided that alkyl substituents protect the vinyl ether double bond from coordination by the metal catalyst.
- Baan, J. L. van der,Bickelhaupt, F.
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p. 6267 - 6270
(2007/10/02)
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- 2-Allylisourea as an Effective Agent for Direct α-Allylation of Ketone and Aldehyde Assisted by Palladium(0) under Neutral Conditions
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Direct α-allylation of a variety of ketones and aldehydes with 2-allylisourea took place in the presence of a catalytic amount of a palladium(0) complex under neutral and mild conditions.Scope and limitations of this novel method have been investigated.
- Inoue, Yoshio,Toyofuku, Masanori,Taguchi, Masaaki,Okada, Shin-ichi,Hashimoto, Harukichi
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p. 885 - 892
(2007/10/02)
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- SYNTHESIS OF SINGLE ISOMERS (E OR Z) OF PROTECTED γ,δ-UNSATURATED KETONES BY THE HORNER-WITTIG REACTION
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The lithium derivative of the γ-diphenylphosphinoyl ketal (10a) added to aldehydes and ketones to give stable Horner-Wittig intermediates (11) which were separated and converted into single isomers (E or Z) or γ,δ-unsaturated ketals (12). erythro-Adducts (11) and hence Z-(12), were selectively formed by addition of aldehydes and threo adducts (11), and hence E-(12), by reduction of the corresponding α-diphenylphosphinoyl ketones (13), prepared by acylation of the same γ-diphenylphosphinoyl ketal (10a).
- Cornish Christopher A.,Warren, Stuart
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p. 2585 - 2598
(2007/10/02)
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- DILITHIO ACETOACETATE AS AN ACETONE ENOLATE EQUIVALENT
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Dilithio acetoacetate, which can be generated from acetoacetic acid and n-butyllithium, undergoes alkylation followed by facile decarboxylation to give methyl ketones.
- Kjonaas, Richard A.,Patel, Dhiren D.
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p. 5467 - 5468
(2007/10/02)
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- Reaction of Aromatic Sulfonyl Azides with Dienes
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THe addition of aromatic sulfonyl azides to simple acyclic and cyclic dienes in a 1:2 molar ratio was investigated.In no case was the triazoline cycloaddition product isolated from the thermal cycloaddition.With the nonconjugated dienes 1,5-hexadiene and 1,7-octadiene, hydrogen migration occurred with nitrogen loss, affording sulfonimide products.No evidence for olefinic participation or alkyl group migration was obtained.Hydrolysis of the sulfonimides gave the corresponding unsaturated ketones 5-hexen-2-one and 7-octen-2-one, respectively.Conjugated dienes reacted with aromatic sulfonyl azides to give enamines rather than sulfonimides.The reaction of p-nitrobenzenesulfonyl azide with 1,3-cyclohexadiene followed by hydrolysis afforded only 2-cyclohexen-1-one resulting from hydrogen migration.Addition to either cis,trans- or trans,trans-2,4-hexadiene gave, after hydrolysis, trans-4-hexen-3-one and trans-2-methyl-2-pentenal arising from competitive hydrogen and vinyl group migration, respectively.
- Abramovitch, Rudolph A.,Ortiz, Margarita,McManus, Samuel P.
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p. 330 - 335
(2007/10/02)
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- Process for the production of allyl acetone
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A process is described for the preparation of allyl acetone (5-hexen-2-one) according to the reaction: STR1 wherein R is methyl or ethyl; X is chloro or bromo; M is sodium or potassium; and Q is sodium or potassium, the reaction being carried out (i) using a phase transfer agent and (ii) in a two phase system.
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