- The effect Of Solvent on Competing Hydroperoxide and Dioxetane Formation on Photo-Sensitized Oxygenation of Olefins
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The rates of the competitive photo-sensitized oxygenation of 2-isobutylidene-adamantane (1) and 2-propylidene-adamantane (2) with 1,1-di-t-butyl-2-methoxyethene (3) in various solvents were determined.The rates for 1 and 2 were independent of solvent, whereas that for 3 varied markedly with solvent polarity.Compounds 1 and 2 gave only hydroperoxides while 3 gave dioxetane.These results are interpreted in terms of two competing processes involving little and much charge separation leading to hydroperoxide and dioxetane, respectively.
- Jefford, Charles W.,Kohmoto, Shigeo
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Read Online
- Dehalogenation of 1,3-diiodotricyclo[3.3.0.03,7]octane: Generation of 1,3dehydrotricyclo[3.3.0.03,7]octane, a 2,5-methano-bridged [2.2.1]propellane
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Compounds isolated from the reaction of (±)-1,3-diiodotricy-clo[3.3. 0.03,7]octane with molten sodium or tBuLi suggest the intermediate formation of (±)-1,3-dehydrotricyclo[3.3.0.03,7]octane. Worthy of note is the formation of stereoisomeric bi(5-methylenebicyclo[2.2.1]hept-2- ylidene) derivatives, probably by coupling of two units of (±)-1,3- dehydrotricyclo[3.3.0.03,7]octane of the same or different absolute configuration followed by fragmentation, processes that have been studied by theoretical calculations.
- Ayats, Carles,Camps, Pelayo,Fernandez, Jose A.,Vazquez, Santiago
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Read Online
- Alcohol oxidation via recyclable hydrophobic ionic liquid-supported IBX
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The first ionic hydrophobic liquid-supported 1-hydroxy-1,2-benziodoxole-3(1H)-one-1-oxide (IBX) reagent was prepared for oxidizing alcohols. In this study, a hydrophobic ionic liquid-supported IBX reagent was synthesized and described. This hydrophobic ionic liquid-supported IBX reagent was able to be recovered and used in a recyclable reaction system by re-oxidation and washing.
- Koguchi, Shinichi,Mihoya, Aya,Mimura, Minato
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p. 7633 - 7637
(2016/11/11)
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- New Organocatalyst scaffolds with high activity in promoting hydrazone and oxime formation at neutral pH
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The discovery of two new classes of catalysts for hydrazone and oxime formation in water at neutral pH, namely 2-aminophenols and 2-(aminomethyl)benzimidazoles, is reported. Kinetics studies in aqueous solutions at pH 7.4 revealed rate enhancements up to 7-fold greater than with classic aniline catalysis. 2-(Aminomethyl)benzimidazoles were found to be effective catalysts with otherwise challenging aryl ketone substrates.
- Larsen, Dennis,Pittelkow, Michael,Karmakar, Saswata,Kool, Eric T.
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supporting information
p. 274 - 277
(2015/03/05)
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- The retro Grignard addition reaction revisited: The reversible addition of benzyl reagents to ketones
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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
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p. 1478 - 1483
(2014/02/14)
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- A reusable unsupported rhenium nanocrystalline catalyst for acceptorless dehydrogenation of alcohols through γ-C-H activation
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Rhenium nanocrystalline particles (Re NPs), of 2 nm size, were prepared from NH4ReO4 under mild conditions in neat alcohol. The unsupported Re NPs convert secondary and benzylic alcohols to ketones and aldehydes, respectively, through catalytic acceptorless dehydrogenation (AD). The oxidant- and acceptor-free neat dehydrogenation of alcohols to obtain dihydrogen gas is a green and atom-economical process for making carbonyl compounds. Secondary aliphatic alcohols give quantitative conversion and yield. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Re K-edge X-ray absorption near-edge structure (XANES), and X-ray absorption fine structure (EXAFS) data confirmed the characterization of the Re NPs as metallic rhenium with surface oxidation to rhenium(IV) oxide (ReO2). Isotope labeling experiments revealed a novel γ-CH activation mechanism for AD of alcohols. Active particles: A rhenium nanoparticle (Re NP) catalyst is generated from NH4ReO4 under mild solution conditions in neat 3-octanol at 180°C. The resulting Re NPs catalyze acceptorless dehydrogenation of alcohols through a novel C-H activation pathway, and are fully recyclable. Copyright
- Yi, Jing,Miller, Jeffrey T.,Zemlyanov, Dmitry Y.,Zhang, Ruihong,Dietrich, Paul J.,Ribeiro, Fabio H.,Suslov, Sergey,Abu-Omar, Mahdi M.
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supporting information
p. 833 - 836
(2014/01/23)
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- Pivaloylmetals (tBu-COM: M=Li, MgX, K) as equilibrium components
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Short-lived pivaloylmetals, (H3C)3C-COM, were established as the reactive intermediates arising through thermal heterolytic expulsion of O=CtBu2 from the overcrowded metal alkoxides tBuC(=O)-C(-OM)tBu2 (M=MgX, Li, K). In all three cases, this fission step is counteracted by a faster return process, as shown through the trapping of tBu-COM by O=C(tBu)-C(CD3)3 with formation of the deuterated starting alkoxides. If generated in the absence of trapping agents, all three tBu-COM species "dimerize" to give the enediolates MO-C(tBu)=C(tBu)-OM along with O=CtBu2 (2 equiv). A common-component rate depression by surplus O=CtBu2 proves the existence of some free tBu-COM (separated from O=CtBu2); but companion intermediates with the traits of an undissociated complex such as tBu-COM & O=CtBu2 had to be postulated. The slow fission step generating tBu-COMgX in THF levels the overall rates of dimerization, ketone addition, and deuterium incorporation. Formed by much faster fission steps, both tBu-COLi and tBu-COK add very rapidly to ketones and dimerize somewhat slower (but still fairly fast, as shown through trapping of the emerging O=CtBu2 by H3CLi or PhCH2K, respectively). At first sight surprisingly, the rapid fission, return, and dimerization steps combine to very slow overall decay rates of the precursor Li and K alkoxides in the absence of trapping agents: A detailed study revealed that the fast fission step, generating tBu-COLi in THF, is followed by a kinetic partitioning that is heavily biased toward return and against the product-forming dimerization. Both tBu-COLi and tBu-COK form tBu-CH=O with HN(SiMe3)3, but only tBu-COK is basic enough for being protonated by the precursor acyloin tBuC(=O)-C(-OH)tBu2. Copyright
- Knorr,Boehrer,Schubert,Boehrer
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experimental part
p. 7506 - 7515
(2012/07/27)
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- Synthesis of sterically hindered ketones from aldehydes via O-silyl oximes
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A mild and efficient method to synthesize sterically hindered ketones from aldehydes via O-silyl oximes was developed. Treatment of O-triphenylsilylated oximes with alkyl iodides in the presence of triethyl borane afforded the corresponding ketones.
- Kim, Joong-Gon,Mishra, Mithilesh Kumar,Jang, Doo Ok
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experimental part
p. 3527 - 3529
(2012/08/29)
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- A general route to fully terminally tert-butylated linear polyenes
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Starting from the readily available α,β-unsaturated ketone, 3-tert-butyl4,4-dimethyl-2-pentenal, higher vinylogues, and fully terminally tert-butylated polyolefins with up to 13 consecutive conjugated double bonds have been prepared by either McMurry dimerization or Wittig chain-elongation routes. The highly unsaturated conjugated π systems, which show a remarkable stability, have been characterized by spectroscopic methods and, in many cases, by X-ray structural analysis. The yields are high enough to allow for thorough chemical reactivity studies.
- Klein, Dagmar,Kilickiran, Pinar,Mlynek, Cornelia,Hopf, Henning,Dix, Ina,Jones, Peter G.
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scheme or table
p. 10507 - 10522
(2010/11/04)
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- Reaction of 3,3-di-tert-butylthiirane-2-thione S-oxide (α-dithiolactone S-oxide): synthesis of thiolato sulfinato-platinum and palladium complexes
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Thermolysis of 3,3-di-tert-butylthiirane-2-thione S-oxide 4 gave di-tert-butyl ketone 5 and carbon disulfide (CS2). Treatment of α-dithiolactone S-oxide 4 with excess m-CPBA or triphenylphosphine gave di-tert-butylthioketene S-oxide 3 almost quantitatively. Treatment of 4 with (η2-ethylene)bis(triphenylphosphine)platinum(0) 13 or tetrakis(triphenylphosphine) palladium 17 resulted in the formation of thiolato sulfinato-platinum complex 15 or palladium complex 18, respectively. The structure of complex 15 was determined by X-ray crystallographic analysis.
- Shigetomi, Toshiyuki,Shioji, Kosei,Okuma, Kentaro,Inoue, Tohru,Yokomori, Yoshinobu
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p. 5161 - 5166
(2008/02/01)
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- Cycloadditions of 3,4-dihydro-2H-pyrrole N-oxide with thioketones and a selenoketone
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Cycloadditions of 2-diphenylphosphinoyl-2-methyl-3,4-dihydro-2H-pyrrole N-oxide (DPhPMPO), 3,4-dihydro-2H-pyrrole N-oxide having a diphenylphosphinoyl group at the C2 position with thioketones afforded the corresponding 1,4,2-oxathiazolidines. Dissociation constants of these 5-membered ring products were determined. The cycloadducts were stabilized by the diphenylphosphinoyl group. The reaction of DPhPMPO with di-tert-butyl selenoketone gave the corresponding selenoamide under microwave irradiation. The formation of the selenoamide indicated that the cycloaddition of DPhPMPO with the selenoketone analogue also proceeded through the formation of the corresponding 5-membered ring product.
- Shioji, Kosei,Matsumoto, Akio,Takao, Masahiko,Kurauchi, Yoshimitsu,Shigetomi, Toshiyuki,Yokomori, Yoshinobu,Okuma, Kentaro
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p. 743 - 746
(2007/10/03)
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- Preparation of 3,3-di-tert-butylthiirane trans-1,2-dioxide and its reaction with a platinum(0) complex to give a (disulfenato)platinum(II) complex: Regioselectivity of the oxidation of a related (sulfenato-thiolato)platinum(II) complex
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A three-membered vic-disulfoxide, 3,3-di-tert-butyldithiirane trans- 1,2-dioxide (8), was synthesized by oxidation of the corresponding dithiirane 1-oxide 15 in high yield. Treatment of 8 and 15 with a platinum(0) complex, [(Ph3P)2Pt(η2-C2H4)], yielded the (disulfenato)PtII complex 18 and the (sulfenato-thiolato)PtII complex 14, respectively, in high yields. Oxidation of the sulfenato-thiolato complex 14 with an acetone solution of dimethyldioxirane (DMD) took place at the sulfenato sulfur atom to yield the (sulfinato-thiolato)PtII complex 19, while the oxidation with CF 3CO3H occurred at the thiolato-sulfur atom leading to the disulfenato complex 18. Oxidation of 14 with MCPBA formed both 18 and 19. The position of oxidation on 14 with DMD was dependent on the acidity of a coexisting acid. Thus, oxidation of 14 with DMD/CF3CO2H provided 18 and that with DMD/PhCO2H gave 19. Oxidation of 14 with an excess amount of DMD yielded the (disulfonato)PtII complex 20. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Ishii, Akihiko,Ohishi, Masayuki,Nakata, Norio
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p. 5199 - 5206
(2008/09/17)
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- Thermal decomposition of O-benzyl ketoximes; role of reverse radical disproportionation
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Thermolyses of seven dialkyl, two alkyl-aryl and two diaryl O-benzyl ketoxime ethers, R1R2C=NOCH2Ph, have been examined in three hydrogen donor solvents: tetralin, 9,10-dihydrophenanthrene, and 9,10-dihydroanthracene. All the oxime ethers gave the products expected from homolytic scission of both the O-C bond (viz., R1R2C=NOH and PhCH3) and N-O bond (viz., R1R2C=NH and PhCH2OH). The yields of these products depended on which solvent was used and the rates of decomposition of the O-benzyl oxime ethers were greater in 9,10-dihydrophenanthrene and 9,10-dihydroanthracene than in tetralin. These results indicated that a reverse radical disproportionation reaction in which a hydrogen atom was transferred from the solvent to the oxime ether, followed by β-scission of the resultant aminoalkyl radical, must be important in the latter two solvents. Benzaldehyde was found to be an additional product from thermolyses conducted in tetralin. This, and other evidence, indicated that another induced decomposition mode involving abstraction of a benzylic hydrogen atom, followed by β-scission of the resulting benzyl radical, became important for some substrates. Participation by minor amounts of enamine tautomers of the oxime ethers was shown to be negligible by comparison of thermolysis data for the O-benzyloxime of bicyclo[3.3.1]nonan-9-one, which cannot give an enamine tautomer, with that of the O-benzyloxime of cyclohexanone.
- Blake, Jessie A.,Ingold, Keith U.,Lin, Shuqiong,Mulder, Peter,Pratt, Derek A.,Sheeller, Brad,Walton, John C.
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p. 415 - 420
(2007/10/03)
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- Low-calcemic oxime analogs of 1alpha,25-dihydroxy vitamin D3
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The present invention provides novel 16-ene-C25-oxime and 16-ene-C-25-oxime ether analogs of 1α,25-dihydroxy vitamin D3, compositions comprising these compounds and methods of using these compounds as inhibitors of CYP24. In particular, the compound of Formula I are useful for treating diseases which benefit from a modulation of the levels of 1α,25-dihydroxy vitamin D3, for example, cell-proliferative disorders.
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- Ozonolyses of 1-alkyl-substituted 1-tert-butylethylenes and highly methylated methylenecycloalkanes. The influence of the substituent steric bulk on the direction of cleavage of the primary ozonides
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Ozonolyses of 1-alkyl-substituted 1-tert-butylethylenes and of highly methylated methylenecycloalkanes were conducted in the presence of trifluoroacetophenone (7) in ether. The ozonolysis of 2,2,6-trimethyl-1-methylenecyclohexane provided only the crossed-ozonide 10 derived from capture of formaldehyde O-oxide with the ketone 7 in 42% yield, while in the case of the relevant 2,2,5-trimethyl-1-methylenecyclopentane the alternative crossed-ozonide 15e derived from cycloaddition of 2,2,5-trimethylcyclopentanone O-oxide with the ketone 7 was the sole isolable product. The total energies of two possible cycloreversion processes for the primary ozonide 12c and for 12e, calculated at B3LYP/6-31G**//B3LYP/3-21G* level of theory, seem to reproduce the observed difference in the regiochemistry of fragmentation between these two primary ozonides.
- Kawamura, Shin-Ichi,Yamakoshi, Hideyuki,Abe, Manabu,Masuyama, Araki,Nojima, Masatomo
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p. 891 - 896
(2007/10/03)
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- A practical method for alcohol oxidation with aqueous hydrogen peroxide under organic solvent- and halide-free conditions
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A catalytic system consisting of sodium tungstate and methyltrioctylammonium hydrogensulfate effects oxidation of simple secondary alcohols to ketones using 3 - 30% H2O2 without any organic solvents. The oxidation can be conducted under entirely halide-free, mildly acidic conditions. A combination of tungstic acid and an appropriate quaternary ammonium salt also effects the alcohol dehydrogenation. The organic/aqueous biphasic reaction allows easy product/catalyst separation. The turnover number, defined as tools of product per mol of catalyst, approaches 77700 (2- octanol) or 179000 (1-phenylethanol), two orders of magnitude higher than any previously reported. Ester, alkyl and t-butyldimethylsilyl ether, epoxy, carbonyl, N-alkyl carboxamide, and nitrile groups are tolerated under the reaction conditions. Secondary alcohols are preferentially oxidized over terminal olefins. Primary alkanols are oxidized directly to carboxylic acids in a moderate to high yield. Benzylic alcohols are selectively oxidized to benzaldehydes or benzoic acids under suitable conditions. This method is high-yielding, clean, safe, operationally simple, and cost-effective, and therefore suitable for practical organic synthesis. The mechanistic origin of the catalytic efficiency is discussed.
- Sato, Kazuhiko,Aoki, Masao,Takagi, Junko,Zimmermann, Klaus,Noyori, Ryoji
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p. 2287 - 2306
(2007/10/03)
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- Hydrogen bonding Part 44 1Thermodynamics of complexation of 3,5-dichlorophenol with ketones and ethers in cyclohexane: The badger-Bauer relationship
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Equilibrium constants for 1 : 1 hydrogen bond complexation between 3,5-dichioropheno' (DCP) and 17 ketones and 12 ethers in cyclohexane solution have been obtained by an FTIR method that takes into account both diiaerization of the acid and formation of 2 :1 complexes. Enthalpies of complexation for the same ketones and ethers have been determined by a calorimeiric method, leading to values of log K, AG, AH and AS0 for 1 :1 complexation in the 29 systems, as well as log K2 for the 2 :1 complexation between 2 mol of acid and 1 mol of base. For the ketone systems there is very little variation in the three thermodynamic parameters with alkyl substitution, but for the ethers there are systematic variations depending on the alkyl substituent or if the ethers are cyclic. Values of the OH stretching frequency in the DCP complexes with the ketones and ethers in cyclohexane have been obtained. The band shapes for the DCP-ketone complexes are very asymmetric, possibly due to the presence of stereoisomeric complexes, but the VOH band for DCP-ether complexes is symmetric and very suitable for the evaluation of any relationship between v()H and A/f. It is found that for the complexation of DCP with the 12 aliphatic ethers in cyclohexane, there is almost no connection between the calorimetrically determined AH° values and values of AvOH.
- Abraham, Michael H.,Prior, David V.,Schulz, Ronald A.,Morris, Jeffrey J.,Taylor, Peter J.
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p. 879 - 885
(2007/10/03)
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- Sterically congested molecules, 17: Novel syntheses of α,α,β-Tri-tert-butyl compounds
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Pivaloin (2), prepared from ethyl pivalate (1) or from dimethyl oxalate (3), reacts with tert-butyllithium by reduction (45% of 10) and addition (45% of 9), whereas the corresponding Barbier variant takes a different course. Productive transformations of the α,α,β-tri-tert-butyl glycol 9 lead to α,β,β-tri-tert-butylethanone (17, overall 4 steps), or α,α,β-tri-tert-butyl-ethene (20, 3 or 4 steps), or α,β,β-tri-tert-butyl-β-hydroxyethanone (19, 3 steps, also by Grignard addition to bipivaloyl 4). Steric congestion is assessed by searches for restricted internal rotation. The alkene 20 and its epoxide 27 are studied with respect to NMR assignments and chemical degradation. VCH Verlagsgesellschaft mbH, 1997.
- Boehrer, Gerald,Knorr, Rudolf,Boehrer, Petra,Schubert, Bernhard
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p. 193 - 202
(2007/10/03)
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- Sterically congested molecules, 16: A convenient synthesis of di-tert-butyl ketone via its imine, 2,2,4,4-tetramethyl-3-pentanimine
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2,2,4,4-Tetramethyl-3-pentanimine (3) is efficiently prepared by a Barbier-type reaction of pivalonitrile (1) with an excess of tert-butyl chloride (2) and metallic lithium in ether. Its purification by extraction into aqueous acid and slow hydrolysis permit an inexpensive and very simple production of di-tert-butyl ketone (4). VCH Verlagsgesellschaft mbH, 1996.
- Knorr, Rudolf,Donhaerl, Angelika,Hennig, Karsten-Olaf
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p. 155 - 157
(2007/10/03)
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- Synthesis of carbonyl and dicarbonyl compounds from organometallic reagents and N-imidazolium-N-methyl amides and bis-amides
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A new method for the synthesis of selective acylating agents is described from the reaction of carboxylic acids with 3-methyl-1-methylamino-3H-imidazol-1-ium salts in the presence of appropriate coupling reagents. The amides and bis-amides thus prepared reacted selectively with organometallics to afford ketones and diketones and with DIBALH to give aldehydes and dialdehydes in high yields.
- De Las Heras, Maria A.,Vaquero, Juan J.,Garcia Navio, Jose L.,Alvarez-Builla, Julio
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p. 14297 - 14310
(2007/10/03)
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- Phosphane Alkylenes, 54. - Synthesis and Properties of Bis(trimethylsilyl) Ketone
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The synthesis of the bis(trimethylsilyl) ketone (1b) by oxydation of triphenylphosphorane (3) is described.The IR, UV, NMR, and PE spectra as well as the cyclovoltagram of this compound are discussed and compared with those of di-tert-butyl ketone (13) and tert-butyl-trimethylsilyl ketone (10). - Key Words: Phosphonium ylides/ Oxidation/ Acylsilanes/ Ketone, bis(trimethylsilyl)/ Ionisation energy
- Bestmann, Hans Juergen,Haas, Wolfgang,Witzgall, Konrad,Ricci, Alfredo,Lazzari, Dario,et al.
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p. 415 - 418
(2007/10/02)
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- Mercury-Photosensitized Sulfination, Hydrosulfination, and Carbonylation of Hydrocarbons: Alkane and Alkene Conversion to Sulfonic Acids, Ketones, and Aldehydes
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Mercury-photosensitized sulfination of alkanes, RH, with SO2 forms sulfinic acids (RSOOH) and sulfinate esters (RSOOR) in high conversion and yield; oxidation of the mixture produces RSO2OH in high yield.Mercury-photosensitized hydrosulfination of alkenes with H2 and SO2 gives RSO2OH after oxidative workup.Mercury-photosensitized carbonylation of alkanes with CO gives RCHO and R2CO.
- Ferguson, Richard R.,Crabtree, Robert H.
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p. 5503 - 5510
(2007/10/02)
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- ALKYLATION OF KETONES BY USE OF SOLID KOH IN DIMETHYLSULFOXIDE
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A mixture of solid KOH in dimethyl sulfoxide has a strong basicity, but only a low nucleophilicity and is used for α-methylation of ketones.With this simple and inexpensive reagent complete methylation with yields up to 90percent can be achieved.
- Langhals, Elke,Langhals, Heinz
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p. 859 - 862
(2007/10/02)
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- ORGANOCOPPER REAGENTS IN DIMETHYL SULFIDE
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Organocopper(I) reagents, RCu, are both more stable and more reactive when prepared in dimethyl sulfide instead of ether or tetrahydrofuran.A wide range of Li reagents has been investigated with good results, as has a selection of Grignard reagents.Excellent yields of products are observed with typical substrates as α,β-unsaturated ketones and acid chlorides.
- Bertz, Steven H.,Dabbagh, Gary
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p. 425 - 434
(2007/10/02)
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- Process for the production of dienes
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Aldehydes can be converted to dienes by contacting the aldehydes with a zeolite or a silica molecular sieve. The zeolite or silica molecular sieves can achieve good conversion rates and selectivities for the reaction. The reaction is especially useful for the conversion of 2-methylbutyraldehyde to isoprene.
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- Steric and Stereoelectronic Effects in the Hydrogenolysis and Birch Reduction of Some Hindered Tertiary-Benzylic Carbinols
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3-(4'-Methoxyphenyl)pentan-3-ol (3a) and 3-(4'-methoxyphenyl)-2,4-dimethylpentan-3-ol (3b) underwent catalytic hydrogenolysis over 10percent palladium/charcoal at moderate temperatures and pressures.The more hindered tertiary-benzylic carbinols 3-(4'-methoxyphenyl)-2,2,4-trimethylpentan-3-ol (6), 3-(4'-methoxyphenyl)-2,2,4,4-tetramethylpentan-3-ol (3c), 1-(4'-methoxyphenyl)-2,2,6,6-tetramethylcyclohexan-1-ol (8) and 1-(1',1'-dimethylethyl)-6-methoxy-2,2-dimethyl-1,2,3,4-tetrahydronaphthalen-1-ol (10) were completely resistant to hydrogenolysis, even under vigorous conditions.While the hindered tertiary-benzylic carbinols (6), (8) and (10) readily underwent Birch reduction, the analogous di-t-butyl anisyl carbinol (3c) was unchanged.The failure of (3c) to undergo Birch reduction is probably due to a hitherto unrecognized stereoelectronic effect: the C-OH bond of (3c) is constrained to lie more or less in the plane of the benzene ring, and addition of an electron to the benzene ring of the derived oxyanion (31) is inhibited in this conformation.
- Collins, David J.,Jacobs, Howard A.
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p. 1989 - 2004
(2007/10/02)
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- The Decomposition of t-Butyl Heptafluoroperoxybutyrate in Aromatic and Aliphatic Solvents
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Kinetical studies and products analyses of the thermal decomposition of t-butyl heptafluoroperoxybutyrate (TBH) in benzene, octane, nitrobenzene, pyridine, and methoxybenzene have been carried out.In benzene and octane, the decoposition appears to be entirely a radical process.In nitrobenzene and pyridine, the reactions are found to give ionic decomposition proudcts exclusively.On the other hand, the decomposition of TBH in methoxybenzene is characteristic of mixed ionic and radical cleavages.
- Sawada, Hideo,Hagii, Hidehiko,Aoshima, Kazuyoshi,Yoshida, Masato,Kobayashi, Michio
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p. 3448 - 3452
(2007/10/02)
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- Radical-cations of Aldehydes and Ketones generated by Ionizing Radiation: an Electron Spin Resonance Study
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Exposure of dilute solutions of various aldehydes and ketones in trichlorofluoromethane to 60Co γ-rays at 77 K gave, in most cases, the corresponding cations, identified by e.s.r. spectroscopy.The acetaldehyde cation is characterized by a very large proton hyperfine coupling, the SOMO being the in-plane, formally non-bonding, p-orbital on oxygen.At 77 K there was a weak interaction with one chlorine atom of a solvent molecule, but this was lost reversibly on annealing to ca. 120 K.That the quartet splitting was due to chlorine rather than to the methyl protons as had been previously supposed was established by studying the (CD3CDO(1+)) cation.The acetone cation spectrum comprised a single asymmetric feature with no evidence of solvent interaction or hyperfine coupling to the γ-protons.In contrast, aldehyde and ketone cations with δ-protons showed hyperfine coupling in the 10-30 G range to conformationally selected protons.For methyl groups, one proton only is selected, the coupling being lost reversibly on annealing.These findings are semi-quantitativelysupported by INDO calculations.
- Boon, Philip, J.,Symons, Martyn, C. R.,Ushida, Kiminori,Shida, Tadamasa
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p. 1213 - 1220
(2007/10/02)
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- Oxidations of Thioketones by Singlet and Triplet Oxygen
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Oxidation of di-tert-butyl thioketone (1) and 2,2,4,4-tetramethylcyclobutyl thioketone (2) by singlet oxygen yields the corresponding sulfine and ketone; in the case of 1 the sulfine is the major product, whereas in 2 it is the ketone. 1,2,3-Dioxathietane has been suggested as the precursor for the ketones, and the zwitterionic/diradical peroxide is believed to be a common primary intermediate for both sulfine and ketone.Steric influence is felt both during primary interaction between singlet oxygen and thioketone and during the partitioning of the peroxide intermediate.Steric interaction is suggested as the reason for variations in the product distribution between 1 and 2.Singlet oxygen is also generated through energy transfer from the triplet state of thioketones.These excited states also directly react with oxygen to yield ketone.
- Rao, V. Jayathirtha,Muthuramu, K.,Ramamurthy, V.
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p. 127 - 131
(2007/10/02)
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- STERIC ASPECTS OF THE OXIDATION OF THIOKETONES BY SINGLET OXYGEN
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Singlet oxygen oxidation of dialkyl thioketones yields the corresponding ketones and in some cases sulfoxides in varying amounts.Steric considerations on the reactive zwitterionic/diradical intermediates have been invoked to rationalise the product distribution.
- Ramnath, Narayan,Jayathertha, Vaidhya Rao,Ramesh, Varadaraj,Ramamurthy, Vaidhyanathan
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- Thiaziridine 1,1-Dioxides
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Experiments towards a 1,3-elimination of hydrogen halides from α-chlorosulfonamides, α-bromosulfonamides, and N-chlorosulfonamides did not yield isolable thiaziridine 1,1-dioxides 4.Therefore, at -78 deg C, the diazoalkanes 10 were allowed to react with N-sulfonylamines 14 generated in situ by hydrogen chloride elimination from sulfamoylchlorides with triethylamine.If the work-up temperature was kept below -30 deg C, from tert-alkyldiazomethanes and tert-alkylsulfamoylchlorides the 2,3-di-tert-alkylthiaziridine 1,1-dioxides 4f - i were obtained in 32 - 47 percent yield.They form colorless, thermally labile crystals.Their structure was based on IR, UV and 1H-NMR spectra as well as on the quantitative thermal decomposition into sulfur dioxide and aldimines.The disubstituted diazomethanes 23 reacted with tert-butylsulfonylamine affording, besides N-tert-butylketimines (the decomposition products of intermediate trisubstituted thiaziridine 1,1-dioxides 21), tert-butylsulfinylamine 25 and ketones 26.The latter products presumably resulted from the cheletropic decomposition of the oxathiiranes 24.
- Quast, Helmut,Kees, Frieder
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p. 774 - 786
(2007/10/02)
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- SYNTHESE EN SERIE ENCOMBREE. PREPARATION DE L'ACIDE DITERTIOBUTYL-METHYLACETIQUE tBu2MeCCOOH ET DE QUELQUES COMPOSES CETONIQUES DERIVES DE CETTE STRUCTURE
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The synthesis of tBu2MeCCOOH, which is among the most sterically hindered known acids is described.Only Newman's sequence via tBu2C=O, tBu2MeCOH, tBu2C=CH2, tBu2CHCH2OH, tBu2CHCOOH, tBu2CHCOCl and tBu2C=C=O, which has been optimized in this work by a direct access to tBu2CHCOOH, permits the preparation of tBu2MeCCOOH.The condensation of the corresponding chloride with a Grignard reagent yields new highly-hindered ketones tBu2MeCCOR wich by alkylation give more substituted structures.The limitations of each method have been studied in this work.
- Dubois, Jacques-Emile,Zhang, Ben Li,Lion, Claude
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p. 4189 - 4194
(2007/10/02)
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- Mechanistic Investigations into the Photochemical Oxidation of Thioketones
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Singlet-oxygen reaction with dialkyl, aryl alkyl, and diaryl thioketones is found to give the corresponding sulphines and ketones in proportions depending on the nature of the thioketone.
- Ramnath, N.,Ramesh, V.,Ramamurthy, V.
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p. 112 - 114
(2007/10/02)
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- Photochemical Oxidation of Thiones: Di-t-butyl Thioketone
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Di-t-butyl thioketone (1) exhibits an anomalous behaviour towards triplet oxygen and yields the corresponding sulphine (3) and the ketone (2) upon irradiation in aerated solutions.Oxidising reagent is suggested to be singlet oxygen in the conversion of thioketone to sulphine and the reactive state of oxygen and thioketone in the formation of ketone (2) is not clear.Mechanism of these conversions is being investigated.
- Rao, V. Jayathertha,Ramamurthy, V.
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p. 143 - 144
(2007/10/02)
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- Catalytic oxidation of thiocarbonyl compounds involving the use of 1,2-Dibrometatrachloroethane as a brominating reagent for diaryl teII species
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1,2-Dibromotetrachloroethane acts as a useful brominating reagent for diaryl TeII species in the establishment of a room temperature catalytic cycle for the conversion of thiocarbonyl compounds to their oxo analogues.
- Ley, Steven V.,Meerholz, Clive A.,Barton, Derek H.R.
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p. 1785 - 1788
(2007/10/02)
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