- Evidence for Electron-transfer Process in Abnormal Gringard Reactions. Enolization and α-Diketone Formation
-
The effect of 2,6-dimethyl groups on enolization vs. addition in the reaction of PhMgBr with PhCH2COPh, and also the formation of α-diketone from 2,4,6-Me3C6H2COCl by the treatment with MeMgX and i-PrMgX in the presence of CoCl2, were studied.The results were discussed on the basis of electron-transfer mechanism.
- Okubo, Masao,Morigami, Yoshiaki,Suenaga, Reiko
-
-
Read Online
- O-H...?(arene) Intermolecular Hydrogen Bonding in the Structure of 1,1,2-Triphenylethanol
-
The 1,1,2-triphenylethanol molecule, Ph2(PhCH2)COH (I), forms centrosymmetric dimers in the solid state.The shortest O...O separation, 5.837(3) Angstroem, is too long for any O-H...O hydrogen-bond formation.Instead, there are O-H...?(arene) interactions between the hydroxyl group of one molecule and a phenyl group of acentrosymmetrically related molecule.The O...C and H...C distances between the hydroxyl group and the closest phenyl-ring C atom are 3.525(4) and 2.73(4) Angstroem, respectively.These intermolecular contacts are the only driving force towards dimer formation in the solid state.
- Ferguson, George,Gallagher, John F.,Glidewell, Christopher,Zakaria, Choudhury M.
-
-
Read Online
- Notable temperature effect on the stereoselectivity in the photochemical [2+2] cycloaddition reaction (Paternò-Büchi reaction) of 2,3-dihydrofuran-3-ol derivatives with benzophenone
-
A notable temperature effect (nonlinear Eyring plot) on stereoselectivity, trans-configured oxetane 2 versus cis-configured oxetane 2, is reported in the photochemical [2+2] cycloaddition reaction (Paternò-Büchi reaction) of 2,3-dihydrofuran-3-ol derivatives 1 with benzophenone.
- Abe, Manabu,Terazawa, Midori,Nozaki, Koichi,Masuyama, Araki,Hayashi, Takashi
-
-
Read Online
- Hydrogen bonding in ferrocene derivatives: crystal structure of racemic ferrocenyl(phenyl)methanol
-
A single-cristal X-ray diffraction study has been carried out on racemic ferrocenyl(phenyl)methanol.There are two independent chiral molecules A and B in the asymmetric unit, and the molecules are linked by OH...O hydrogen bonds into zigzag chains characterized by the motif -S(A)-R(B)-R(A)-S(B)-; within these chains the two independent hydrogen-bonded O...O distances are 3.059(2) and 3.150(2) Angstroem.Key words: Ferrocene; Hydrogen bonding; Crystal structure
- Ferguson, George,Gallagher, John F.,Glidewell, Christopher,Zakaria, Choudhury M.
-
-
Read Online
- Iron-catalysed 1,2-aryl migration of tertiary azides
-
1,2-Aryl migration of α,α-diaryl tertiary azides was achieved by using the catalytic system of FeCl2/N-heterocyclic carbene (NHC) SIPr·HCl. The reaction generated aniline products in good yields after one-pot reduction of the migration-resultant imines.
- Wei, Kaijie,Yang, Tonghao,Chen, Qing,Liang, Siyu,Yu, Wei
-
p. 11685 - 11688
(2020/10/19)
-
- Photocatalytic Barbier reaction-visible-light induced allylation and benzylation of aldehydes and ketones
-
We report a photocatalytic version of the Barbier type reaction using readily available allyl or benzyl bromides and aromatic aldehydes or ketones as starting materials to generate allylic or benzylic alcohols. The reaction proceeds at room temperature under visible light irradiation with the organic dye 3,7-di(4-biphenyl)1-naphthalene-10-phenoxazine as a photocatalyst and DIPEA as sacrificial electron donor. The proposed cross-coupling mechanism of a ketyl- and an allyl or benzyl radical is supported by spectroscopic investigations and cyclic voltammetry measurements.
- Berger, Anna Lucia,Donabauer, Karsten,K?nig, Burkhard
-
p. 7230 - 7235
(2018/10/02)
-
- Iron-Catalyzed Nucleophilic Addition Reaction of Organic Carbanion Equivalents via Hydrazones
-
Earth-abundant and well-defined iron complexes are found to be cheap and effective catalysts for a series of "umpolung" nucleophilic additions of hydrazones. The new catalytic system not only maintains the broad substrate scope of an earlier expensive ruthenium system but also attains chemoselectivity of different kinds of carbonyl groups. Furthermore, the iron catalyst enables this reaction at ambient temperature.
- Li, Chen-Chen,Dai, Xi-Jie,Wang, Haining,Zhu, Dianhu,Gao, Jian,Li, Chao-Jun
-
supporting information
p. 3801 - 3805
(2018/07/25)
-
- Aldehydes as alkyl carbanion equivalents for additions to carbonyl compounds
-
Nucleophilic addition reactions of organometallic reagents to carbonyl compounds for carbon-carbon bond construction have played a pivotal role in modern chemistry. However, this reaction's reliance on petroleum-derived chemical feedstocks and a stoichiometric quantity of metal have prompted the development of many carbanion equivalents and catalytic metal alternatives. Here, we show that naturally occurring carbonyls can be used as latent alkyl carbanion equivalents for additions to carbonyl compounds, via reductive polarity reversal. Such 'umpolung' reactivity is facilitated by a ruthenium catalyst and diphosphine ligand under mild conditions, delivering synthetically valuable secondary and tertiary alcohols in up to 98% yield. The unique chemoselectivity exhibited by carbonyl-derived carbanion equivalents is demonstrated by their tolerance to protic reaction media and good functional group compatibility. Enantioenriched tertiary alcohols can also be accessed with the aid of chiral ligands, albeit with moderate stereocontrol. Such carbonyl-derived carbanion equivalents are anticipated to find broad utility in chemical bond formation.
- Wang, Haining,Dai, Xi-Jie,Li, Chao-Jun
-
p. 374 - 378
(2017/04/03)
-
- Benzyllithiums bearing aldehyde carbonyl groups. A flash chemistry approach
-
Reductive lithiation of benzyl halides bearing aldehyde carbonyl groups followed by reaction with subsequently added electrophiles was successfully accomplished without affecting the carbonyl groups by taking advantage of short residence times in flow microreactors.
- Nagaki, Aiichiro,Tsuchihashi, Yuta,Haraki, Suguru,Yoshida, Jun-ichi
-
supporting information
p. 7140 - 7145
(2015/07/01)
-
- α-Alkylidene-γ-butyrolactone synthesis via one-pot C-H insertion/olefination: substrate scope and the total synthesis of (±)-cedarmycins A and B
-
Abstract A system for the synthesis of α-alkylidene-γ-butyrolactones via a one-pot C-H insertion/olefination sequence is described. The process is based on the rhodium catalysed C-H insertion reaction of α-diazo-α-(diethoxyphosphoryl)acetates. The mild reaction conditions, operational simplicity and ready availability of starting materials are all key features. A wide range of successful reaction systems are reported (41 examples) highlighting the generality of the method. The application of this method in the total synthesis of the natural products (±)-cedarmycins A and B is also described.
- Lloyd, Matthew G.,D'Acunto, Mariantonietta,Taylor, Richard J.K.,Unsworth, William P.
-
p. 7107 - 7123
(2015/02/19)
-
- A simple and efficient copper oxide-catalyzed Barbier-Grignard reaction of unactivated aryl or alkyl bromides with ester
-
An efficient one-pot route to synthesize tertiary alcohol compounds using Barbier-Grignard reaction of unactivated alkyl or aryl bromides with ester in THF at 65 C catalyzed by CuO has been developed and systematically investigated. A wide range of substituted tertiary alcohol compounds were obtained in good to high yields. The reaction is highly chemoselective. The mechanism involving the leaving group of R2O-group is discussed.
- Gao, Fei,Deng, Xiang-Jun,Tang, Yu,Tang, Jin-Peng,Yang, Jun,Zhang, Yuan-Ming
-
supporting information
p. 880 - 883
(2014/02/14)
-
- A simple and efficient copper oxide-catalyzed Barbier-Grignard reaction of unactivated aryl or alkyl bromides with ester
-
An efficient one-pot route to synthesize tertiary alcohol compounds using Barbier-Grignard reaction of unactivated alkyl or aryl bromides with ester in THF at 65 °C catalyzed by CuO has been developed and systematically investigated. A wide range of substituted tertiary alcohol compounds were obtained in good to high yields. The reaction is highly chemoselective. The mechanism involving the leaving group of R2O-group is discussed.
- Gao, Fei,Deng, Xiang-Jun,Tang, Yu,Tang, Jin-Peng,Yang, Jun,Zhang, Yuan-Ming
-
supporting information
p. 880 - 883
(2015/03/03)
-
- The retro Grignard addition reaction revisited: The reversible addition of benzyl reagents to ketones
-
The Grignard addition reaction is known to be a reversible process with allylic reagents, but so far the reversibility has not been demonstrated with other alkylmagnesium halides. By using crossover experiments it has been established that the benzyl addition reaction is also a reversible transformation. The retro benzyl reaction was shown by the addition of benzylmagnesium chloride to di-tert-butyl ketone followed by exchange of both the benzyl and the ketone moiety with another substrate. Similar experiments were performed with phenylmagnesium bromide and tert-butylmagnesium chloride, but in these two cases the Grignard addition reaction did not show any sign of a reverse transformation.
- Christensen, Stig Holden,Holm, Torkil,Madsen, Robert
-
p. 1478 - 1483
(2014/02/14)
-
- Catalyst-controlled highly selective coupling and oxygenation of olefins: A direct approach to alcohols, ketones, and diketones
-
Oxygen? That's radical! A method for the direct synthesis of substituted alcohols, ketones, and diketones through a catalyst-controlled highly chemoselective coupling and oxygenation of olefins has been developed. The method is simple and practical, can be switched by the selection of different catalysts, and employs molecular oxygen as both an oxidant and a reagent. Copyright
- Su, Yijin,Sun, Xiang,Wu, Guolin,Jiao, Ning
-
supporting information
p. 9808 - 9812
(2013/09/23)
-
- Doing the methylene shuffle - Further insights into the inhibition of mitotic kinesin Eg5 with S-trityl l-cysteine
-
S-Trityl l-cysteine (STLC) is an inhibitor of the mitotic kinesin Eg5 with potential as an antimitotic chemotherapeutic agent. We previously reported the crystal structure of the ligand-protein complex, and now for the first time, have quantified the interactions using a molecular dynamics based approach. Based on these data, we have explored the SAR of the trityl head group using the methylene shuffle strategy to expand the occupation of one of the hydrophobic pockets. The most potent compounds exhibit strong (100 nM) inhibition of Eg5 in the basal ATPase assay and inhibit growth in a variety of tumour-derived cell lines.
- Abualhasan, Murad N.,Good, James A.D.,Wittayanarakul, Kitiyaporn,Anthony, Nahoum G.,Berretta, Giacomo,Rath, Oliver,Kozielski, Frank,Sutcliffe, Oliver B.,MacKay, Simon P.
-
experimental part
p. 483 - 498
(2012/09/10)
-
- Intramolecular nucleophilic attack at silicon in o-silylbenzyl alcohols. Generation of allyl and benzyl anion equivalents
-
Substituted silyl ethers of o-bromobenzyl alcohols and the derived o-silylbenzyl alcohols were used to transfer allyl and benzyl groups from silicon to the electrophiles benzaldehyde and benzophenone in excellent yields. γ-Oxidosilane intermediates (and possibly hypercoordinated silicon intermediates) are postulated.
- Hudrlik, Paul F.,Hudrlik, Anne M.,Jeilani, Yassin A.
-
body text
p. 10089 - 10096
(2012/02/13)
-
- Hydroxy-group effect on the regioselectivity in a photochemical oxetane formation reaction (the Paterno-Buechi Reaction) of geraniol derivatives
-
The Paterno-Buechi (PB) reaction of geraniol derivatives 1, which contain allylic alcohol functionality and unfunctionalized double bonds, with benzophenone was investigated to see the effect of the hydroxyl group on the regioselectivity of the oxetane formation, i.e., 2/3. At low concentration of geraniol (1a), oxetanes 2a and 3a were formed in a ratio of 2a/3a = ca. 50/50. The oxetane 2a is derived from the PB reaction at the allylic alcohol moiety, whereas the PB reaction at the unfunctionalized double bond produces the oxetane 3a. The PB reaction of the hydroxy-protected methyl ether 1b and acetate 1c gave selectively oxetanes 3b,c derived from the reaction at the more nucleophilic double bond, 2/3 ~ 15/85. The hydroxyl-group effect was found to be small, but apparently increased the formation of 2a in the PB reaction with geraniol (1a). The Royal Society of Chemistry and Owner Societies.
- Hisamoto, Ken,Hiraga, Yoshikazu,Abe, Manabu
-
experimental part
p. 1469 - 1473
(2012/06/18)
-
- A mild oxidative aryl radical addition into alkenes by aerobic oxidation of arylhydrazines
-
A mild and practical oxyarylation of alkenes by oxidative radical addition has been developed by using aerobic oxidation of hydrazine compounds. The use of a catalytic amount of potassium ferrocyanide trihydrate (K4[Fe(CN) 6]·3 H2O) and water accelerated this radical reaction to give peroxides or alcohols from simple alkenes in good yields. The environmentally friendly and economical radical reactions were achieved at room temperature in the presence of iron catalyst, oxygen gas, and water. A method involving aniline as a radical precursor is also described. Copyright
- Taniguchi, Tsuyoshi,Zaimoku, Hisaaki,Ishibashi, Hiroyuki
-
experimental part
p. 4307 - 4312
(2011/05/07)
-
- Concentration and temperature dependency of regio- and stereoselectivity in a photochemical [2 + 2] cycloaddition reaction (the Paterno-Buechi reaction): Origin of the hydroxy-group directivity
-
A set of photochemical oxetane formation reactions, i.e., the Paterno-Buechi (PB) reactions, of tetrahydrobenzofuranol derivatives 1a-d with benzophenone (BP) was investigated to examine poorly understood hydroxy-group directivity on regio- and stereoselectivity. The selectivities of the PB reactions for allylic alcohols 1a,d were found to be largely dependent upon the concentration of the allylic alcohols and the reaction temperature. The temperature-dependent change of the regioselectivity at high concentrations of allylic alcohols was similar to that of the hydroxy-protected methyl ether 1b and tetrahydrobenzofuran (1c). The effect of concentration on regioselectivity can be explained by the hydrogen-bonded aggregates, which mimic the selectivities observed during the PB reaction of 1b,c. The hydroxy-directed cis-selectivity of the higher-substituted oxetane 3a,d formed at low concentration of 1a,d was found to be larger than that at the higher concentration of 1a,d. The cis-selectivity of 3a,d was found to be higher than that of the lower-substituted oxetane 2a,d. The regioselectivity of the cis-configured oxetanes was higher than that of the trans-configured oxetanes. These experimental results strongly suggest that hydroxy-group directivity, induced by hydrogen-bonding stabilization, plays a role in controlling the regio- and stereoselectivity of the PB reactions. The steric effect was also responsible for the diastereoselectivity, as shown by the fact that the cis selectivity in 3d was higher than that in 3a. Computational studies at the (U)MP2 and (U)DFT level of theory revealed that hydrogen-bonding stabilization becomes important only in the excited complex (exciplex) between the triplet excited state of carbonyls and alkenes, in which the charge transfer occurs from the alkene to the excited carbonyl to make the carbonyl oxygen nucleophilic. No significant stabilization energy was found in the intermediary triplet state of biradicals. The combined experimental and computational studies have clarified the origin of the poorly understood hydroxy-group effect on a high degree of regio- and stereoselectivity, i.e., the cooperative effect of hydrogen-bonding stabilization in exciplexes and the steric bulk of the substituents.
- Yabuno, Youhei,Hiraga, Yoshikazu,Takagi, Ryukichi,Abe, Manabu
-
experimental part
p. 2592 - 2604
(2011/04/23)
-
- Photo-allylation and photo-benzylation of carbonyl compounds using organotrifluoroborate reagents
-
Allyl- and benzyl-trifluoroborates can be applied to the photoreaction of carbonyl compounds to afford the corresponding alcoholic adducts in acceptable yields via a photo-induced single electron transfer pathway. The results were confirmed from the react
- Nishigaichi, Yutaka,Orimi, Takayuki,Takuwa, Akio
-
experimental part
p. 3837 - 3839
(2010/03/04)
-
- Highly efficient alkylation to ketones and aldimines with Grignard reagents catalyzed by zinc(II) chloride
-
A highly efficient alkylation to ketones and aldimines with Grignard reagents in the presence of catalytic trialkylzinc(II) ate complexes derived from ZnCl2 (10 mol %) in situ was developed. This simple Zn(II)-catalyzed alkylation could minimize the well-known but serious problems with the use of only Grignard reagents, which leads to reduction and aldol side products, and the yield of desired alkylation products could be improved. Copyright
- Hatano, Manabu,Suzuki, Shinji,Ishihara, Kazuaki
-
p. 9998 - 9999
(2007/10/03)
-
- DUTPASE INHIBITORS
-
Deoxyuridine derivatives of the formula (I) where R1 is H or various substituents; D is -NHCO-, -CONH-, -0-, -C(=O)-, -CH=CH, -CΞC-, -NR5-; R4 is hydrogen or various substituents; R5 is H, C1-C4 alkyl, C1-C4 alkanoyl; E is Si or C; R6, R7 and R8 are independently selected from C1-C8 alkyl, C2-C8 alkenyl, C2-C8 alkynyl or a stable monocyclic, bicyclic or tricyclic ring system; G is -O-, -S-, -CHR10-, -C(=O)-; J is -CH2-, or when G is CHR10 may also be -O- or -NH-; R10 is H, F, -CH3, -CH2NH2, -CH2OH; -OH R11 is H, F, -CH3, -CH2 NH2, -CH2OH, CH(OH)CH3, CH(NH3)CH3; or R10 and R11 together define an olefinic bond, or together form a -CH2-group, thereby defining a cis or trans cyclopropyl group; have utility in the prophylaxis or treatment of protozoal diseases such as malaria.
- -
-
Page/Page column 52
(2008/06/13)
-
- 2,2-(Diaryl)vinylphosphine compound, palladium catalyst thereof, and process for producing arylamine, diaryl, or arylalkyne with the catalyst
-
A novel 2,2-(diaryl)vinylphosphine compound represented by the following general formula (1): (wherein R1 is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alicyclic group having 5 to 7 carbon atoms, etc.; R2, R3, R4, R5, R6, and R7 may be the same or different and each is an alkyl group having 1 to 6 carbon atoms, an alicyclic group having 5 to 7 carbon atoms, etc., provided that R4 and R5 taken together and/or R6 and R7 taken together may represent a fused benzene ring, a substituted fused benzene ring, a trimethylene group, etc.; and p, q, r, and s each is 0 to 5, provided that p+q and r+s each is in the range of from 0 to 5); a palladium-phosphine catalyst obtained by causing a palladium compound to act on the novel 2,2-(diaryl)vinylphosphine compound; and a process for obtaining an arylamine, a diaryl and an arylalkyne in the presence of the palladium-phosphine catalyst.
- -
-
-
- Generation of allylic and benzylic organolithium compounds by fluorine-lithium exchange: Reaction with electrophiles
-
The application of the naphthalene-catalysed lithiation methodology to allylic and benzylic fluorides 1 led to the corresponding allylic and benzylic organolithium reagents, which, in the presence of different electrophiles (Barbier-type reaction conditions), afforded the expected products 2 in moderate yields. The procedure was useful for the transformation of primary, secondary and tertiary benzylic fluorides into the corresponding lithium derivatives. When a two-step lithiation process was used (treatment of fluoride 1 with lithium and a catalytic amount of naphthalene, followed by addition of the electrophilic reagent), only Wurtz-type coupling products were formed.
- Guijarro, David,Yus, Miguel
-
-
- Alkoxides of o-silyl benzyl alcohols in cleavage reactions: Approaches to benzyl and silyl anion equivalents
-
The alkoxides of o-silyl benzyl alcohols 4 undergo cleavage reactions under mild conditions allowing transfer of a benzyl or silyl group to an electrophile. Reactions 3a → 8, and 3c or 4c → 11 illustrate their potential as benzyl and silyl anion equivalents.
- Hudrlik, Paul F.,Arango, Jose O.,Hijji, Yousef M.,Okoro, Cosmas O.,Hudrlik, Anne M.
-
p. 1421 - 1427
(2007/10/03)
-
- Generation of Anionic Intermediates by Intramolecular Nucleophilic Attack at Silicon
-
Benzyl and allyl anion equivalents can be generated from benzyl- and allylsilanes by intramolecular alkoxide attack.
- Hudrlik, Paul F.,Abdallah, Yousef M.,Hudrlik, Anne M.
-
p. 6747 - 6750
(2007/10/02)
-
- Naphthalene-Catalysed Lithiation of Allylic and Benzylic Mesylates: A New Method for Allyl, Methallyl, and Benzyl Lithium
-
The reaction of allylic or benzylic mesylates (1) with an excess of lithium powder and a catalytic amount of naphthalene (4 mol percent) in THF at -78 deg C leads to a solution of the corresponding organolithium derivatives, which by treatment with different electrophiles yield the expected products 2-7.As an alternative route, the process can be carried out at 0 deg C by adding the corresponding mesylate together with the electrophile to a suspension of the activated lithium in THF, in a Barbier-type reaction.
- Guijarro, D.,Mancheno, B.,Yus, M.
-
p. 4593 - 4600
(2007/10/02)
-
- Reactions of Thermally Generated tert-Butyl and Di(tert-alkyl)ketyl Radicals in Toluene: Cage Effects and Hydrogen Transfer
-
Thermolysis of di(1-adamantyl)-tert-butylmethanol (2a) in toluene at 145-185 deg C gives mainly bibenzyl, di(1-adamantyl) ketone, di(1-adamantyl)methanol, and the cross-product, 1,1-di(1-adamantyl)-2-phenylethanol.In the presence of benzophenone (BP) or benzenethiols as hydrogen-accepting and hydrogen-donating radical scavengers, respectively, the di(1-adamantyl)methanol/di(1-adamantyl) ketone ratio tends to steady values as the scavenger/2a ratio is increased, while the cross-product disappears.At 165 deg C the secondary alcohol minimum is 8percent (BP) and the ketone minimum 11percent (thiol).These represent the contributions of geminate hydrogen atom transfer reactions to the overall yields, i.e., the cage effects.With BP the major cross-product is 1,1,2-tri-phenylethanol.Products from the self- and cross-reactions of benzyl and thiyl radicals are found when thiol is present, the diaryl disulfide predominating at high thiol concentration.In both cases, cross-products resulting from reaction of the tert-butyl radical with the scavenger-derived radical are detected in small amounts, being of greater importance in deuteriated toluene.The tert-butyl radical is considered, therefore, to be less reactive in hydrogen atom abstraction than the 1-adamantyl radical.Cage effects for other di(tert-alkyl)-tert-butylmethanols that thermolyze with exclusive t-Bu-C bond fission have also been measured and the product composition of the scavenger-free reaction interpreted by kinetic simulation based on the steady state approximation.Rate constants for hydrogen abstraction by the tert-butyl radical from toluene are not accurately determined by this procedure but seem, nevertheless, to indicate that the literature value (14.4 M-1s-1 at 48 deg C) is an overestimate. Solvent hydrogen abstraction by the ketyl radical shows a small but well-defined steric effect.
- Lomas, John S.,Briand, Sylvette,Fain, Dominique
-
p. 166 - 175
(2007/10/02)
-
- Reactions of Thermally Generated 1-Adamantyl and Di(1-adamantyl)ketyl Radicals in Toluene
-
Thermolysis of tri(1-adamantyl)methanol in toluene at 145-185 deg C gives bibenzyl, di(1-adamantyl)ketone, di(1-adamantyl)methanol and a cross-product, 1,1-di(1-adamantyl)-2-phenylethanol, in yields which depend on the temperature and the isotopic composition of the solvent.In the presence of benzophenone the intermediate di(1-adamantyl)ketyl radical transfers hydrogen, giving ketone and the hydroxybenzhydryl radical, the cross-product then being 1,1,2-triphenylethanol.The cage effect (0.38-0.415) has been determined by studying thermolysis in deuterium labeled toluene.In normal toluene almost all the secondary alcohol is formed from Ad2C*OH by hydrogen abstraction from the solvent, whereas in deuterated toluene 22-32percent results from self-disproportionation of ketyl radicals, showing that there is a substantial kinetic isotope effect on hydrogen abstraction.Kinetic modeling of the reaction by means of a rapid, iterative procedure based on the steady-state approximation suggests values in the range 6.0-7.4, decreasing as the temperature rises.
- Lomas, John S.,Fain, Dominique,Briand, Sylvette
-
p. 1052 - 1058
(2007/10/02)
-
- HYDROGEN ATOM TRANSFER IN THE REACTIONS OF THERMALLY-GENERATED DI-t-ALKYLKETYL AND 1-ADAMANTYL RADICALS
-
In the thermolysis of tri-(1-adamantyl)methanol about 55percent of the di-(1-adamantyl)-ketyl amd 1-adamantyl radicals escape from the solvent cage, the former transferring hydrogen to benzophenone and the second abstracting hydrogen from the solvent, toluene, with isotope effects on the latter reaction consistent with tunnelling.
- Lomas, John S.,Briand, Sylvette
-
p. 707 - 710
(2007/10/02)
-
- Photochemistry of Diphenylketyl Radicals: Spectroscopy, Kinetics, and Mechanisms
-
The photochemistry of the diphenylketyl radical has been examined in nonpolar solutions.Transient studies using two-laser techniques yield an excited-state lifetime of 3.9 ns in toluene at room temperature, while for diphenylketyl-O-d the lifetime is 8.7 ns.Dye laser irradiation (515 nm) in the kethyl's visible absorption band leads to efficient photobleaching with Φbleach=0.27 +/- 0.06 for the parent radical and 0.39 and 0.26 for the 4-methyl and 4-chloro derivatives, respectively.The photobleaching reaction involves the cleavage of the O-H ketyl bond to yield benzophenone and hydrogen atoms; in cyclohexane the latter abstract hydrogen from the solvent to produce molecular hydrogen, which was characterized by Raman spectroscopy.In accordance with this mechanism, two-laser experiments produce lower yields of photoreduction products than the one-laser experiments in which the ketyls are not photobleached.When the ketyl radicals are generated by reaction of tert-butoxy radicals with benzhydrol, dye laser irradiation leads to a large increase in the yield of benzophenone (now a product), although the mechanism here is somewhat more complex due to the quenching of excited ketyl radicals by di-tert-butyl peroxide (kq=1.9E9 M-1s-1).Detailed studies of the fluorescence, isotope effects, temperature effects, and products are also included.
- Johnston, Linda J.,Lougnot, D. J.,Wintgens, Veronique,Scaiano, J. C.
-
p. 518 - 524
(2007/10/02)
-
- Indirect Electrochemical Reduction of Vinyl Halides and Related Compounds
-
Some substituted vinyl halides and related compounds have been reduced indirectly by electrolysis using anion radicals as mediators.The rate of electron transfer from the electron donors to the electron acceptors has been measured by cyclic voltammetry, and the solvent and bond reorganization energy, λ, has been extracted from the data using the Marcus equation.The λ values for the vinyl and cyclopropyl halides were found to be closer to those for aryl halides than those for alkyl halides.The method was used preparatively for selective dehalogenation of vinyl halides, including derivatives of 10-bromo-5H-dibenzazepine.
- Gatti, Norberto,Jugelt, Werner,Lund, Henning
-
p. 646 - 652
(2007/10/02)
-
- Le benzyltrimethylsilane, un agent pratique de benzylation
-
In the presence of Bu4N(1+))*F(1-), benzyltrimethylsilane behaves as a convenient benzylation reagent.In the reaction with non conjugated aldehydes, pehenethylalcohols are obtained in satisfactory yields upon hydrolysis, while the formation of bibenzyl or ortho products are not observed.When the reaction occurs with α,β-unsaturated aldehydes and ketones, only 1,2-addition is observed even in the case of chalcone.
- Bennetau, Bernard,Bordeau, Michel,Dunogues, Jacques
-
-
- UN NOVEAU SYNTHON ORGANOSILICIE: LE BENZYLTRIMETHYLSILANE
-
In the presence of tetrabutylammonium fluoride (TBAF) as the catalyst, benzyltrimethylsilane adds to aldehydes and ketones to afford, upon hydrolysis, the corresponding alcohols.The use of PhCH2SiMe3 as a general benzylation reagent is here reported for the first time.
- Bennetau, Bernard,Dunogues, Jacques
-
p. 4217 - 4218
(2007/10/02)
-
- REACTIONS OF PHENYLYTTERBIUM ? COMPLEX WITH CARBONYL COMPOUNDS: A NEW GRIGNARD-TYPE REAGENT HAVING UNUSUAL REACTIVITY TOWARD ESTERS AND KETONES
-
Phenylytterbium iodide has been found to react with ketones, aldehydes, esters, and nitriles to give alcohols and/or ketones.The reactions with esters at low temperature give ketones as main products, and the reactivity of esters to Ph-Yb-I is higher than that of ketones in contrast to the Grignard reaction.
- Fukagawa, Toshihiro,Fujiwara, Yuzo,Yokoo, Kazuhiro,Taniguchi, Hiroshi
-
p. 1771 - 1774
(2007/10/02)
-