- Fast Addition of s-Block Organometallic Reagents to CO2-Derived Cyclic Carbonates at Room Temperature, Under Air, and in 2-Methyltetrahydrofuran
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Fast addition of highly polar organometallic reagents (RMgX/RLi) to cyclic carbonates (derived from CO2 as a sustainable C1 synthon) has been studied in 2-methyltetrahydrofuran as a green reaction medium or in the absence of external volatile organic solvents, at room temperature, and in the presence of air/moisture. These reaction conditions are generally forbidden with these highly reactive main-group organometallic compounds. The correct stoichiometry and nature of the polar organometallic alkylating or arylating reagent allows straightforward synthesis of: highly substituted tertiary alcohols, β-hydroxy esters, or symmetric ketones, working always under air and at room temperature. Finally, an unprecedented one-pot/two-step hybrid protocol is developed through combination of an Al-catalyzed cycloaddition of CO2 and propylene oxide with the concomitant fast addition of RLi reagents to the in situ and transiently formed cyclic carbonate, thus allowing indirect conversion of CO2 into the desired highly substituted tertiary alcohols without need for isolation or purification of any reaction intermediates.
- Elorriaga, David,de la Cruz-Martínez, Felipe,Rodríguez-álvarez, María Jesús,Lara-Sánchez, Agustín,Castro-Osma, José Antonio,García-álvarez, Joaquín
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p. 2084 - 2092
(2021/04/02)
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- ETHERS AND ESTERS OF TERTIARY ALKANOLS FOR USE AS AROMA CHEMICALS
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The present invention relates to the use of an ether or an ester of a tertiary alkanol or of mixtures of two or more ethers or esters of tertiary alkanols or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof as aromachemicals; to the use thereof for modifying the scent character of a fragranced composition; to an aroma chemical composition containing an ether or an ester of tertiary alkanol or of mixtures of two or more ethers or esters of tertiary alkanols or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof; and to a method of preparing a fragranced composition or for modifying the scent character of a fragranced composition. The invention further relates to specific ethers or esters of tertiary alkanols.
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- Controllable Intramolecular Unactivated C(sp3)-H Amination and Oxygenation of Carbamates
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Dual catalyst-controlled intramolecular unactivated C(sp3)-H amination and oxygenation of carbamates merging visible-light photocatalysis and earth-abundant transition metal catalysis have been reported. Useful amino alcohol and diol derivatives could be selectively obtained from readily available tertiary alcohol derivatives. The possible mechanisms have been proposed via a 1,5-HAT process followed by Lewis acid-controlled cyclization. The nickel and zinc catalysts inhibit the formation of oxygenation and amination products, respectively. An interesting phenomenon of chirality transfer is also observed.
- Guo, Qihang,Ren, Xiang,Lu, Zhan
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supporting information
p. 880 - 884
(2019/05/16)
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- Factors affecting migration of tertiary alkyl groups in reactions of alkylboronic esters with bromomethyllithium
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The reactions of bromomethyllithium with tert-alkylboronic esters could be of great potential for the formation of quaternary carbon centers but often give poor yields/conversions. Calculations and experimental evidence show that tert-alkyl groups migrate less effectively than other types of alkyl group in such reactions and that O-migration competes. Furthermore, slow/incomplete capture of the bromomethyl reagent by the boronic ester is a problem in more hindered systems, and an additional competing reaction, possibly Li-Br exchange on the bromomethylborate species, also leads to lower yields of migrated products. Based on this, experimental protocols have been devised in which the competing reactions are largely suppressed, leading to higher conversions to migrated product for several substrates.
- Elliott, Mark C.,Smith, Keith,Heulyn Jones,Hussain, Ajaz,Saleh, Basil A.
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p. 3057 - 3064
(2013/06/27)
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- Highly regioselective reaction of zirconocene-alkene complexes with aldehydes or ketones
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Reactions of zirconocene-alkene complexes Cp2Zr(CH2=CHR)(PR'3) (R = H, Me, Et, SiR"3 or Ar) with aldehydes or ketones were investigated.Zirconocene-ethylene, -propylene or 1-butene complexes reacted with aldehydes or ketones at terminal carbons of alkenes to give the corresponding alcohols after hydrolysis with a high regioselectivity.A similar type of reaction product was also obtained by a reaction of zirconacyclopentanes with aldehydes.This reaction proceeded via β-β' carbon-carbon bond cleavage of zirconacyclopentanes.A reaction of zirconocene-vinylsilane complexes with ketones afforded 3-trimethylsilyl-1-oxa-2-zirconacyclopentanes with an excellent regioselectivity.Carbon-carbon bond formation occurred exclusively at the terminal carbon of vinylsilanes.Their corresponding γ-silylalcohols were obtained after hydrolysis.The products showed that vinylsilanes reacted with carbonyl compounds at the β-carbon to silyl group.It is in sharp contrast to the conventional reactions of vinylsilanes of which the α-carbon normally attacked electrophiles.The reactions of styrene and its derivatives with pentan-3-one on zirconium gave a mixture of two regioisomers.Substituents of alkenes tend to be in α-position to Zr in 1-oxa-2-zirconacyclopentanes.This orientation showed a different aspect of the formation of 1-oxa-2-zirconacyclopentanes from the alkene-alkene coupling reaction on zirconium.The regioselectivity of the reaction with carbonyl compounds decreased in this order; R = alkyl > silyl > aryl. Key words: Zirconium; Silicon; Metallocenes; Carbon-carbon bond formation; Aldehyde; Ketone
- Suzuki, Noriyuki,Rousset, Christophe J.,Aoyagi, Koichiro,Kotora, Martin,Takahashi, Tamotsu,et al.
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p. 117 - 128
(2007/10/02)
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- Diorganomagnesium Compounds from Magnesium, Hydrogen, and 1-Alkenes and Their Application in Synthesis
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1-Alkenes are converted in high yields to the corresponding primary diorganomagnesium compounds by transition metal-catalyzed hydromagnesation reaction using catalytically prepared suspended (MgH2*) or dissolved magnesium hydride (MgH2').The most active hydromagnesation catalysts have been found to be combinations of zirconium tetrahalides with MgH2* or MgH2'.The reaction is highly regio- and chemoselective.The diorganomagnesium compounds prepared in situ from magnesium, hydrogen, and 1-alkenes can be applied to the synthesis of organic and organometallic compounds just as Grignard compounds (Scheme 3, reactions 3-11).Dioctylmagnesium undergoes the growth reaction with ethene in the presence of quinuclidine and is oxidized by molecular oxygen in high yield to 1-octanol. Key Words: Magnesium hydride, catalytically prepared / Hydromagnesation reactions / Magnesium, diorgano compounds, preparation from magnesium, hydrogen and 1-alkenes / Magnesium, diorgano compounds, application in syntheses / Magnesium, diorgano compounds, oxidation of
- Bogdanovic, Borislav,Bons, Peter,Konstantinovic, Stanimir,Schwickardi, Manfred,Westeppe, Uwe
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p. 1371 - 1384
(2007/10/02)
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- The Conformational Behaviour of 10-Substituted Spirodecanes
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The conformational behaviour of 10-X-substituted 1,4-dioxa- and 1,4,6-trioxaspirodecanes 1-4 has been studied by 13C-, 19F- and 1H-NMR spectroscopy.Two X-ray analyses of (2a,e) are presented, and their implications to cleavage reactions of chiral acetals are discussed.Participation of twist boat forms in the conformeric equilibrium of at least 1c has been made plausible by observing 13C, 19F-NMR coupling constants.The ratios of axial to equatorial conformers in 1-4 have been calculated by molecular mechanics.
- Wolff, J. Jens,Frenking, Gernot,Harms, Klaus
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p. 551 - 561
(2007/10/02)
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- On the oxidation of 3-ethylpentane under GifIV and Gif-orsay conditions
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The oxidation of 3-ethylpentane under GifIV (and GoAggII) conditions affords, as major product, 3-acetylpentane and not diethylketone as previously reported. The discrepancy is explained by radical chain autoxidation in presence of a weak tertiary C - H bond.
- Barton, Derek H. R.,Doller, Dario,Ozbalik, Nubar,Balavoine, Gilbert,Gref, Aurore,Boivin, Jean
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p. 353 - 356
(2007/10/02)
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- Pyrolysis of 3-Ethylpent-2-ene - a Further Evidence for a Homoallylic-Rearrangement
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The pyrolysis of 3-ethylpent-2-ene has been studied under conditions of steam cracking in the temperature range 600-700 deg C in a laboratory scale tubular reactor.The main products of decomposition were methane, 2-ethylbutadiene and isoprene.The majority of products obviously arose from H abstraction and radical addition, typical for radical chain reactions in olefins decomposition including phenomena resulting from allylic resonance.The formation of isoprene, however, could only be explained by a reaction network including a homoallylic rearrangement.
- Bach, G.,Zychlinski, W.,Kopinke, F.-D.,Zimmermann, G.
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p. 677 - 682
(2007/10/02)
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- FUNCTIONALISATION OF SATURATED HYDROCARBONS. Part X. A COMPARATIVE STUDY OF CHEMICAL AND ELECTROCHEMICAL PROCESSES (GIF AND GIF-ORSAY SYSTEMS) IN PYRIDINE, IN ACETONE AND IN PYRIDINE-CO-SOLVENT MIXTURES
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Six saturated hydrocarbons (cyclohexane, 3-ethylpentane, methylcyclopentane, cis- and trans-decalin and adamantane) were oxidised by the Gif system (iron catalyst, oxygen, zinc, carboxylic acid) and its electrochemical equivalent (Gif-Orsay system).Results obtained using various solvents (pyridine, acetone, pyridine-acetone mixtures) were similar for both systems.Total or partial replacement of pyridine with acetone affects the selectivity for secondary positions and lowers the ketone/secondary alcohol ratio.The formation of the same ratio of cis- and trans-decal-9-ol from both cis- and trans-decalin clearly demonstrates that tertiary alcohols result from a mechanism essentially radical in nature.
- Belavoine, Gilbert,Barton, Derek H. R.,Boivin, Jean,Gref, Aurore,Coupanec, Pascale Le,et al.
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p. 1091 - 1106
(2007/10/02)
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- ORGANOSELENIUM COMPOUNDS. IV. METHYL (ARYLSELENO)FORMATES, SYNTHESIS AND PROPERTIES
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The synthesis of methyl (arylseleno)formates, based on the reaction of (arylseleno)magnesium bromides with methyl chloroformate, is described.Some characteristics of the methyl (arylseleno)formates are given.
- Lapkin, I. I.,Dedugov, A. N.,Pavlova, N. N.
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p. 309 - 311
(2007/10/02)
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- Chemical and Spectroscopic Observations on the Properties and Composition of Higher Order, Mixed Organocuprates, R2Cu(CN)Li2
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The nature of organocuprates of general formula R2Cu(CN)Li2, derived from CuCN and 2RLi, is described in terms of their structural integrity in solution.A combination of chemical and spectroscopic tests conclusively demonstrates facile dissociation-reassociation of alkyl groups on copper.Data derived from both IR and variable temperature NMR spectra suggest that different aggregation states between Et2O and THF based solutions of these reagents exist.
- Lipshutz, Bruce H.,Kozlowski, Joseph A.,Wilhelm, Robert S.
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p. 3943 - 3949
(2007/10/02)
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- Substitution Reactions of Secondary Halides and Epoxides with Higher Order, Mixed Organocuprates, R2Cu(CN)Li2: Synthetic, Stereochemical, and Mechanistic Aspects
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Higher order cuprates, represented by the general formula R2Cu(CN)Li2, are readily prepared from copper cyanide and 2 equiv of an organolithium.These novel reagents react readily and efficiently with secondary unactivated iodides and bromides affording products of substitution.Likewise, mono-, di-, and trisubstituted epoxides undergo ring opening leading to the corresponding alcohols in excellent yields.The effects of solvent, temperature, gegenion, and variations in ligands are discussed.Replacement of the second equivalent of RLi by CH3Li strongly encouragestransfer of R over CH3 in R(CH3)Cu(CN)Li2 with halides.Use of PhLi as RRLi in place of one RTLi (i.e.RT(Ph)Cu(CN)Li2) is suggested for oxirane cleavage.The stereochemical implications associated with both couplings are also addressed.
- Lipshutz, Bruce H.,Wilhelm, Robert S.,Kozlowski, Joseph A.,Parker, David
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p. 3928 - 3938
(2007/10/02)
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- REACTION OF DIALKYLMAGNESIUM WITH CARBON MONOXIDE AND NITROSODURENE
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Reaction between diethylmagnesium and carbon monoxide gives rise to the formation of pentanone-3, pentanol-3, 3-ethylpentanol-3, 3-ethyl-3-hydroxyhexanone-4 and 3-ethylhexanone-4.The use of CO and application of C NMR spectroscopy revealed that C2H5COCH(C2H5)2 arose after hydrolysis of C2H5COC(C2H5)2MgC2H5.Reaction between (C2H5)2Mg and nitrosodurene proceeds according to the nitrene-radical mechanism and the EPR spectrum presents a signal derived from Me4PhN(radical)-N(PhMe4)OMgC2H5.Upon this basis a carbene-radical mechanism is proposed for the reaction between carbon monoxide and diethylmagnesium.
- Sobota, Piotr,Nowak, Marek,Kramarz, Wanda
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p. 161 - 168
(2007/10/02)
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- Chemistry of Higher Order, Mixed Organocuprates. 5. On the Choice of the Copper(I) Salt for the Formation of R2CuLi
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Chemical and spectroscopic studies are presented that have been designed to manifest differences in reagent composition and reactivity between mixtures of CuI/2RLi and CuSCN/2RLi.The results indicate that while both Cu(I) salts are reported to serve as precursors to lower order cuprates R2CuLi, CuSCN may actually be forming a higher order, mixed species R2Cu(SCN)Li2.This would explain the discrepancy in coupling reactions of each solution with similar organic substrates under otherwise identical conditions.The presence of added lithium salts demonstrates that while Li I added to CuSCN/2RLi has essentially no effect, introduction of an equivalent of LiSCN to CuI/2RLi dramatically alters the efficiency of ligand transfer.
- Lipshutz, Bruce H.,Kozlowski, Joseph A.,Wilhelm, Robert S.
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p. 546 - 550
(2007/10/02)
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- THE APPLICATION OF FREE RADICALS TO THE CATALYTIC SYNTHESIS OF CARBON MONOXIDE DERIVATIVES
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The chemical reactions of carbon monoxide with (C2H5)2Mg and C2H5MgBr in the presence of the carbonyls Mo(CO)6, W(CO)6, Co2(CO)8 and Fe2(CO)9 in tetrahydrofuran have been examined.Catalytic reaction produced a series of compounds.The tetrahydrofuranyl-2-ethyl ketone was the main reaction product, indicating the radical character of the reaction.
- Sobota, Piotr,Kaczurba, Eleonora
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p. 295 - 300
(2007/10/02)
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- Stereochemistry of Aliphatic Carbocations, 13. Protonated Cyclopropanes as Intermediates in 1,2-Alkyl Shifts
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The nitrous acid deamination of 2-ethyl-1-methylbutylamine (10), 1,2-diethylbutylamine (35), and 2-ethyl-1-methylpentylamine (43) has been studied with respect to 1,2-alkyl shifts.Optically active and deuterated amines were employed whenever possible.The structure, configuration, and deuterium distribution of various products (e. g. 16 from 10, 40 and 48 from 35, 56 from 43) are most reasonably explained in terms of alkyl-bridged intermediates (corner-protonated cyclopropanes) which isomerize via proton shifts from corner to corner.The alternative interconversion of open ions via 1,3-H shifts is incompatible with our experimental results.
- Kirmse, Wolfgang,Loosen, Karin,Prolingheuer, Ernst-Christoph
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p. 129 - 141
(2007/10/02)
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