- THIOCARBONYLS INTO CARBONYLS: EFFICIENT CONVERSION BY CLAY-SUPPORTED FERRIC NITRATE
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A simple and inexpensive procedure is proposed for achieving the title transformation.The method works best with thiobenzophenones (60-100percent yields.
- Chalais, Stephane,Cornelis, Andre,Laszlo, Pierre,Mathy, Arthur
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- Gold nanoparticles supported on the periodic mesoporous organosilicas as efficient and reusable catalyst for room temperature aerobic oxidation of alcohols
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Gold nanoparticles supported on the channels of a bifunctional periodic mesoporous organosilica, were found to be a highly efficient catalyst system for the aerobic oxidation of various types of alcohols into their corresponding aldehydes and ketones at room temperature. The catalyst showed no significant loss of efficiency for the aerobic oxidation of benzyl alcohol to give benzaldehyde after 7 reaction cycles. Copyright
- Karimi, Babak,Esfahani, Farhad Kabiri
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- Ferric(III) nitrate supported on kieselguhr: A new reagent for selective oxidation of alcohols
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A selective and effective oxidation of alcohols into the corresponding aldehydes and ketones, respectively, with a new reagent, ferric(III) nitrate supported on kieselguhr, under heterogeneous conditions is reported. Copyright Taylor & Francis Group, LLC.
- Lou, Ji-Dong,Zhu, Long-Hua,Ma, Yi-Chun,Li, Li
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- Aerobic oxidation of alcohols catalyzed by in situ generated gold nanoparticles inside the channels of periodic mesoporous organosilica with ionic liquid framework
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In situ generated gold nanoparticles inside the nanospaces of periodic mesoporous organosilica with an imidazolium framework (Au?PMO-IL) were found to be highly active, selective, and reusable catalysts for the aerobic oxidation of activated and nonactivated alcohols under mild reaction conditions. The catalyst was characterized by nitrogen adsorption-desorption measurement, thermogravimetric analysis (TGA), transmission electron microscopy (TEM), elemental analysis (EA), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The catalyst exhibited excellent catalytic activity in the presence of either Cs2CO3 (35 °C) or K2CO3 (60 °C) as reaction bases in toluene as a reaction solvent. Under both reaction conditions, various types of alcohols (up to 35 examples) including activated benzylic, primary and secondary aliphatic, heterocyclic, and challenging cyclic aliphatic alcohols converted to the expected carbonyl compounds in good to excellent yields and selectivity. The catalyst was also recovered and reused for at least seven reaction cycles. Data from three independent leaching tests indicated that amounts of leached gold particles were negligible (0.2 ppm). It is believed that the combination of bridged imidazolium groups and confined nanospaces of PMO-IL might be a major reason explaining the remarkable stabilization and homogeneous distribution of in situ generated gold nanoparticles, thus resulting in the highly active and recyclable catalyst system.
- Bigdeli, Akram,Karimi, Babak,Khodadadi Karimvand, Somaiyeh,Khorasani, Mojtaba,Safari, Ali Asghar,Vali, Hojatollah
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supporting information
p. 70 - 79
(2020/06/08)
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- B(C6F5)3-Catalyzed Hydrosilylation of Vinylcyclopropanes
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A hydrosilylation of vinylcyclopropanes (VCPs) catalyzed by the strong boron Lewis acid B(C6F5)3 is reported. For the majority of VCPs, little or no ring opening of the cyclopropyl unit is observed. Conversely, for VCPs with bulky R groups, such as ortho-substituted aryl rings or branched alkyl residues, ring opening is the exclusive reaction pathway. This finding is explained by the thwarted hydride delivery to a sterically shielded, β-silicon-stabilized cyclopropylcarbinyl cation intermediate.
- He, Tao,Long, Peng-Wei,Oestreich, Martin
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supporting information
p. 7383 - 7386
(2020/10/12)
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- A double-ring propyl alkone improved process for synthesizing (by machine translation)
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The invention discloses a double-ring improved process for synthesizing propyl alkone. First of all, the reaction is an inert organic solvent in the presence of and solid sodium alcoholate, γ? Butyrolactone dehydration condensation between the molecules occurs, produce intermediate; then to the adding concentrated hydrochloric acid in the reaction system, generating a decarboxylation reaction, 1,7? Dichloroborane? 4? Heptanone crude; finally, in action ShiShimonoseki ahead into a double-ring n-propyl ketone. The invention has the advantage of using an inert organic solvent and solid sodium alcoholate, does not need the recovery carries on mellowly is greatly improved controllability and reaction, reduction reaction by-product, the product yield is higher than the conventional technical 15-20%, the production cost is reduced, reducing the environmental pressure, product quality is improved. (by machine translation)
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Paragraph 0037-0039
(2017/03/28)
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- Synergistic catalysis within TEMPO-functionalized periodic mesoporous organosilica with bridge imidazolium groups in the aerobic oxidation of alcohols
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Anchoring 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) within the nanospaces of a periodic mesoporous organosilica with bridged imidazolium groups led to an unprecedented powerful bifunctional catalyst (TEMPO@PMO-IL-Br), which showed enhanced activity in the metal-free aerobic oxidation of alcohols. The catalyst and its precursors were characterized by N2 adsorption-desorption analysis, transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), thermal gravimetric analysis (TGA), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), solid state electron paramagnetic resonance (EPR) spectroscopy, elemental analysis, transmission electron microscopy (TEM) and high resolution TEM. It was clearly found that the catalytic activity of SBA-15-functionalized TEMPO (TEMPO@SBA-15) not bearing IL, TEMPO@PMO-IL-Cl, PMO-IL-AMP, or individual catalytic functionalities (PMO-IL/TEMPO@SBA-15) was inferior as compared with those obtained from TEMPO@PMO-IL-Br in the metal-free aerobic oxidation of benzyl alcohol, suggesting the critical role of co-supported TEMPO and imidazolium bromide in obtaining high catalytic activity in the described catalyst system. Our observation clearly points to the fact that the combination of imidazolium bromide units in close proximity to TEMPO moieties in the nanospaces of TEMPO@PMO-IL-Br might be indeed one of the key factors explaining the enhanced catalytic activity observed for this catalyst in the oxidation of benzyl alcohol, possibly through a synergistic catalysis relay pathway. A proposed model was suggested for the observed synergistic effect.
- Karimi, Babak,Vahdati, Saleh,Vali, Hojatollah
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p. 63717 - 63723
(2016/07/19)
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- SBA-15-Functionalized 3-Oxo-ABNO as Recyclable Catalyst for Aerobic Oxidation of Alcohols under Metal-Free Conditions
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The nitroxyl radical 3-oxo-9-azabicyclo [3.3.1]nonane-N-oxyl (3-oxo-ABNO) has been prepared using a simple protocol. This organocatalyst is found to be an efficient catalyst for the aerobic oxidation of a wide variety of alcohols under metal-free conditions. In addition, the preparation and characterization of a supported version of 3-oxo-ABNO on ordered mesoporous silica SBA-15 (SABNO) is described for the first time. The catalyst has been characterized using several techniques including simultaneous thermal analysis (STA), transmission electron microscopy (TEM), and nitrogen sorption analysis. This catalyst exhibits catalytic performance comparable to its homogeneous analogue and much superior catalytic activity in comparison with (2,2,6,6-tetramethylpiperidin-1-yl)oxy (TEMPO) for the aerobic oxidation of almost the same range of alcohols under identical reaction conditions. It is also found that SABNO can be conveniently recovered and reused at least 12 times without significant effect on its catalytic efficiency.
- Karimi, Babak,Farhangi, Elham,Vali, Hojatollah,Vahdati, Saleh
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p. 2735 - 2741
(2016/12/23)
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- A highly recyclable magnetic core-shell nanoparticle-supported TEMPO catalyst for efficient metal- and halogen-free aerobic oxidation of alcohols in water
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The selective oxidation of primary and secondary alcohols to the corresponding carbonyl compounds is one of the most challenging reactions in organic chemistry. Many oxidizing reagents such as stoichiometric CrVI salts, DMSOcoupled reagents, and hypervalent iodine have been traditionally used to accomplish this transformation. However, these reagents show poor atom efficiency and are often toxic; their widespread use thereby causes significant environmental concerns that render them impractical. As a consequence, due to ever-increasing environmental standards and economic pressures, there is substantial interest towards the use of heterogeneous and recyclable catalysts to achieve the efficient oxidation of alcohols with molecular oxygen or air as the oxidant. Whereas methodologies for the improvement of catalytic activities and selectivities have been developed considerably, they may possibly leave toxic traces of heavy metals in the products. Moreover, many of the metal-based catalyst systems are often deactivated because of the occupation of coordination sites with the by-produced water and so they generally require the use of organic solvents. Therefore, it seems that there is still a great interest in developing efficient and non-metallic catalysts for the aerobic oxidation of alcohols from the viewpoint of socalled green and sustainable chemistry. Of particular interest in this area is the application of the stable nitroxyl radical 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) in combination with various types of non-metallic, stoichiometric co-oxidants as an alternative to metal-based oxidants.
- Karimi, Babak,Farhangi, Elham
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supporting information; experimental part
p. 6056 - 6060
(2011/06/26)
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- Shaken not stirred; Oxidation of alcohols with sodium dichromate
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Efficient and selective oxidation of primary alcohols to the corresponding aldehydes with sodium dichromate at room temperature under solvent-free conditions by shaking is described. This new procedure can also successfully oxidise secondary alcohols.
- Lou, Ji-Dong,Gao, Chun-Ling,Ma, Yi-Chun,Huang, Li-Hong,Li, Li
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p. 311 - 313
(2007/10/03)
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- An efficient selective oxidation of alcohols with potassium permanganate adsorbed on aluminum silicate under solvent-free conditions and shaking
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A new procedure for the selective oxidation of alcohols to the corresponding aldehydes and ketones with potassium permanganate supported on aluminum silicate at room temperature under solvent-free conditions and shaking is reported. Springer-Verlag 2006.
- Lou, Ji-Dong,Gao, Chun-Ling,Li, Li,Fang, Zhi-Gang
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p. 1071 - 1074
(2007/10/03)
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- Processes for the preparation of aryl-β-diketones, arylpyrimidine ketones and crop protection intermediates
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This invention relates to processes for the preparation of aryl-β-diketones and aryl-pyrimidine ketones. In addition, this invention relates to the preparation of aryl-β-triketones and dimethyl aminomethylene β-diketones, which are useful as crop protection intermediates.
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- Synthesis of 3-alkoxy-3-aryl-4,4-diisopropyl-1,2-dioxetanes and their base-induced chemiluminescence
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Low-temperature singlet oxygenation of 1-alkoxy-1-aryl-2,2- diisopropylethylenes (9) gives the corresponding 1,2-dioxetanes (10) in high selectivity. Dioxetanes (10) are thermally stable enough to permit handling at room temperature, though an alkoxy group affects significantly their thermal stability and the order of half-life is MeO > tert- BuO. On treatment with tetrabutylammonium fluoride in DMSO, dioxetanes (10e - 10h) bearing a m-siloxyphenyl decompose rapidly to emit intense blue light with ΦCL > 0.2. For the base-induced decomposition of 10e - 10h, the order of rate of decomposition is MeO EtO i-PrO tert-BuO.
- Watanabe, Nobuko,Suganuma, Hiroyuki,Kobayashi, Hisako,Mutoh, Hiroshi,Katao, Yuriko,Matsumoto, Masakatsu
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p. 4287 - 4298
(2007/10/03)
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- 4-cycloalkyl-5-substituted pyrimidine compounds useful as crop protection agents
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Herbicidal 4-cycloalkyl-5-substituted pyrimidine compounds of the formula STR1 are described. Herbicidal compositions containing such substituted-pyrimidinyl compounds and methods of controlling undesirable vegetation employing these compounds are also disclosed. The compounds in which XR, is hydroxyl are also useful as intermediates for producing the disclosed substituted-pyrimidinyl derivatives.
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- Dimerization of cyclopropanecarbonitrile mediated by Grignard reagents. Formation of highly substituted pyridines
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The reaction of cyclopropanecarbonitrile with ethylmagnesium bromide in diethyl ether followed by quenching with malononitrile gave the expected 2-cyano-3-cyclopropylpent-2-enonitrile (1a) in high yields. When the solvent was changed to tetrahydrofuran (THF) using ethylmagnesium chloride, low yields of 1a (12%) were obtained; the main products were two pentasubstituted pyridines, 2-amino-5-(2-chloroethyl)-3-cyano-6-cyclopropyl-4-ethylpyridine (2a, 70%) and 2-amino-3-cyano-5-(3,3-dicyanopropyl)-6-cyclopropyl-4-ethylpyridine (2c, 10%). In addition, their isomers, 2-amino-5-(2-chloroethyl)-3-cyano-4-cyclopropyl-6-ethylpyridine (3a, 7%) and 2-amino-3-cyano-5-(3,3-dicyanopropyl)-4-cyclopropyl-6-ethylpyridine (3c, 1%), were observed and identified by combined gas chromatography-mass spectrometry (GC-MS). When methyl-magnesium chloride was used (solvent THF), in addition to 1b and the isomers 2d, 2e, 3d and 3e, a tetrasubstituted pyridine, 2-amino-3-cyano-4,6-dicyclopropylpyridine (11), was formed. Similar reaction between cyclopropyl-magnesium bromide and cyclopropanecarbonitrile gave after hydrolysis about equal yields of dicyclopropyl ketone and a diketone, 1,1-di(cyclopropane-carbonyl)cyclopropane (8b). The structures of 2c and 2d were established by X-ray crystallography. Acta Chemica Scandinavica 1997.
- Kolsaker, Per,Songe, Pal,Romming, Christian
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p. 1104 - 1111
(2007/10/03)
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- N-CARBOETHOXYPIPERIDINE, A CONVENIENT REAGENT FOR THE PREPARATION OF SYMMETRICAL KETONES FROM ORGANOLITHIUMS
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N-Carboethoxypiperidine on reaction with organolithium reagents, RLi, followed by acidic work-up gave excellent yields of the corresponding symmetrical ketones, R2CO.
- Prakash, G. K. Surya,York, Chentao,Liao, Qimu,Kotian, Kirtivan,Olah, George A.
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- 3,3-Dicyclopropyl-1,2-dioxetanes: Unusual Temperature Effect on the Singlet Oxygenation of 1,1-Dialkylethylenes
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The reaction temperature has a significant effect on the singlet oxygenation of a vinylcyclopropane 5 to yield an allylic hydroperoxide 6 and a dioxetane 7.
- Matsumoto, Masakatsu,Suganuma, Hiroyuki
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p. 2449 - 2450
(2007/10/02)
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- Synthesis of 1,2-Dioxolanes by Ozonolysis of 1,1-Disubstituted Nonactivated Olefins
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Ozonolyses of the cyclopropyl-substituted olefins 2a, 2b, and 2c do not produce the carbonyl oxides 1a, 1b, and 1c but formaldehyde oxide (1d); 1d can be trapped by the starting olefin and provides the 1,2-dioxolanes 6a, 6b, and 6c, respectively, in ca. 10percent yield.Other dioxolanes and normal ozonides may be obtained by the addition of olefins or aldehydes to solutions of the primary ozonides of 2a and 2b.Key-Words: Ozonolysis / Alkylidenecycloalkanes / Carbonyl oxides / 1,2-Dioxolanes / 1,2,4-Trioxolanes
- Reiser, Ralf,Seeboth, Rolf-Guenter,Sueling, Carsten,Wagner, Gabriele,Wang, Jinkai,Schroeder, Gerhard
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p. 191 - 195
(2007/10/02)
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- Unique Thermal Isomerization of the Diels-Alder adduct of 1,1-Dicyclopropylspirohepta-4,6-diene
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The Diels-Alder adduct of 1,1-dicyclopropylspirohepta-4.6-diene (2a) with TCNE underwent unique rearrangement to give an imine derivative, whose formation may be explained by retro-Diels-Alder-re-attack of TCNE at the β position of 2a followed by an extensive isomerization involving the Cope rearrangement.
- Nishida, Shinya,Asanuma, Naoki,Tsuji, Takashi,Imai, Toshiro
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p. 495 - 498
(2007/10/02)
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- Reaction of Thioketones with Carbonyl Oxides and 3,3-Dimethyl-1,2-dioxirane. Cycloaddition vs. Oxygen Atom Transfer
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The ozonolysis of vinyl ethers 1a, b in the presence of adamantane-2-thione 4a and bicyclononan-9-thione 4b gave in each case the corresponding thioozonides 5a-c in moderate yields, whilst ozonolysis of a mixture of vinyl ethers 1a-d and thiobenzophenone derivatives 4f-h gave the corresponding thione S-oxides 8f-h in isolated yields of 10-40percent, together with the benzophenones 7f-h. 3,3-Dimethyl-1,2-dioxirane, generated in situ from the reaction of acetone and 'oxone' (2KHSO5-KHSO4-K2SO4), transferred an oxygen atom to compounds 4a, f, g, i providing the thione S-oxides 8a, f, g, i in 29-97 percent yield.
- Tabuchi, Toshihiko,Nojima, Masatomo,Kusabayashi, Shigekazu
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p. 3043 - 3046
(2007/10/02)
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- One-flask preparation of symmetrical ketones and 1,2-diketones from esters
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A convenient one-flask preparation of a series of symmetrical 1,2-diketones from esters is reported using sodium metal induced acyloin condensation followed by reaction with thionyl chloride. Symmetrical monoketones were obtained when after initial acyloin condensation, the reaction mixture is oxidized with aqueous sodium bromate and then reacted with thionyl chloride. Preparative aspects, the scope of the reaction, and the suggested mechanism are discussed.
- Olah,Wu
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p. 1177 - 1179
(2007/10/02)
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- Chemistry of Dicyclopropylcarbene and Related Intermediates in Dimethyl Sulfoxide
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The potassium salts of the anions of (phenylsulfonyl)hydrazones of diisopropyl, isopropyl cyclopropyl, and dicyclopropyl ketone were decomposed in dimethyl sulfoxide in the temperature range of 110-130 deg C.The diisopropyl phenylsulfonyl anion decomposes to form 2,4-dimethyl-2-pentene and diisopropyl ketone.Similar decomposition of the isopropyl cyclopropyl substrate forms 1-cyclopropyl-2-methylpropene, 1-isopropylcyclobutene, and isopropyl cyclopropyl ketone, while thermal decomposition of the dicyclopropyl ketone (phenylsulfonyl)-hydrazone anion forms cyclopropylcyclobutene and dicyclopropyl ketone.The rate constants for the first and second steps of the consecutive first-order decomposition of the (phenylsulfonyl)hydrazone anions were determined over the temperature range of 110-130 deg C.The activation parameters ΔH* (kcal/mol), ΔS* (eu), and ΔG* (kcal/mol) were calculated for the diazo compound to carbene step (k2) for the diisopropyl (15.6 +/- 1.1, -30.9 +/- 2.8, and 27.7 +/- 1.6), the isopropyl cyclopropyl (27.7 +/- 2.0, 3.3 +/- 5.1, and 26.4 +/- 2.8), and the dicyclopropyl (36.8 +/- 1.8, 28.4 +/- 4.6, 25.6 +/- 2.5).These results are discussed in terms of two factors: interaction of the cyclopropane ring with the functional group and orientation of the polar solvent.
- Freeman, Peter K.,Wuerch, Stephen E.,Clapp, Gary E.
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p. 2587 - 2590
(2007/10/02)
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- CYCLOPROPANATION OF β-KETO SULFONES
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Cyclopropyl β-keto sulfones have been prepared from simple β-keto sulfones in moderate yields using mild reaction conditions which employ potassium carbonate and dimethylformamide (DMF).
- Thomsen, Marcus W.,Handwerker, Beth M.,Katz, Stephanie A.,Fisher, Susan A.
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p. 1433 - 1436
(2007/10/02)
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- Vinyl Cations. 41. Influence of 4-Aryl and 4-Alkyl Substituents on the ?-Route Solvolyses of Homopropargyl Esters
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The four 4-substituted-homopropargyl tosylates and triflates 6b-e (R=phenyl, p-tolyl, anisyl, and cyclopropyl) have been synthesized and solvolyzed under various conditions, as have 2-cyclopropyl-1-cyclobutenyl triflate (11-OTf) and nonaflate (11-ONf).In addition, the solvolyses of pent-3-yn-1-yl tosylate (6a-OTs, R=methyl) and triflate (prepared previously) are reported.The ratios of C-3 ring to C-4 ring 3 ring/C4ring)> products are recorded for the reactions in various solvents.As expected, ring closure (kΔ) increases and solvent displacement (kS, SN2) decreases with decreasing nucleophilicity of solvent.Temperature effects are noted for the sovolyses of tosylates 6a-e in 100percent TFE buffered with Na2CO3 in which kΔ increases with increasing temperature.The result is explained by decomposition of the intimate ion pair with temperature, whereupon elimination to the enyne becomes smaller and ring closure (kΔ) increases at the expense of elimination.The possibility of intervention of nonclassical vinyl cations is discussed, as are other mechanistic implications.
- Collins, Clair J.,Hanack, Michael,Stutz, Herbert,Auchter, Gerhard,Schoberth, Winfried
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p. 5260 - 5268
(2007/10/02)
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- Generation and Chemical Properties of Dicyclopropylcarbene. Ring Expansion, Chlorine Abstraction, C-H Insertion, and Alkene Addition Reactions
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Thermolysis of 5,5-dicyclopropyl-2-methoxy-2-methyl-Δ3-1,3,4-oxadiazoline in solution at 80 deg C affords dicycloproylcarbene and methyl acetate in high yields.Dicyclopropylcarbene undergoes a variety of reactions including ring expansion to 1-cyclopropylcyclobutene, chlorine atom abstraction from carbon tetrachloride, and efficient insertion into the CH bond of chloroform.A rationale for the very different reactions of the carbene with CCl4 and CHCl3 is suggested.Carbene trapping by addition to tetrachloroethylene, using the oxadiazoline as the carbene source, is illustrated with the preparation of an adduct.
- Bekhazi, Michel,Risbood, Prabhakar A.,Warkentin, John
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p. 5675 - 5679
(2007/10/02)
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- Dimerization of Cyclopropanecarboxylic Acid Dianion and Thermal Decarboxylative Rearrangement of the Dimer to 2-Cyclopropyl-4,5-dihydrofuran
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The dianion of cyclopropanecarboxylic acid (2) reacted with alkyl halides and deuterated water at temperatures below 0 deg C; however, self-condensation to the β-keto acid 3 was the only observed product at elevated temperatures.This observation contrasts the self-condensation of the ethyl ester where a trimeric diester alcohol is the product.Attempted mixed condensations of the dianion 2 and carboxylic acids without acidic α-protons did not proceed as well, 3 being the major product.Thermal decarboxylation of 3 did not yield the expected dicyclopropyl ketone; rather , a facile rearrangement in a sealed tube at 120 deg C occured, giving rise to 2-cyclopropyl-4,5-dihydrofuran.This "vinyl-cyclopropyl" type rearrangement does not occur through dicyclopropyl ketone or its enolate.
- Jahngen, Edwin G. E.,Phillips, Douglas,Kobelski, Robert J.,Demko, Donald M.
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p. 2472 - 2476
(2007/10/02)
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- (Acyloxy)carbenes from Thermolysis of Oxadiazolines in Solution. 1-Acetoxyethylidene and 1-Acetoxypropylidene
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Thermolysis of 2-acetoxy-5,5-dicyclopropyl-2-methyl-Δ3-1,3,4-oxadiazoline in CCl4 at 79.5 deg C afforded biacetyl, acetyl chloride, and dicyclopropyl ketone, among other products.It is proposed that the oxadiazoline loses nitrogen, in the first step, to form a carbonyl ylide.The latter then fragments, primarily to dicyclopropyl ketone and 1-acetoxyethylidene .That carbene is partitioned between 1,2 acyl transfer to form biacetyl and abstraction of Cl from CCl4 to form 1-acetoxy-1-chloroethyl radical.The latter undergoes β scission to formacetyl chloride and acetyl radical, which in turn abstracts from CCl4 to form more acetyl chloride.Similarly, 2-acetoxy-5,5-dicyclopropyl-2-ethyl-Δ3-1,3,4-oxadiazoline decomposed in CCl4 to form 2,3-pentanedione, acetyl chloride, propionyl chloride, dicyclopropyl ketone, and other products.Again, the α-diketone is accounted for in terms of an (acyloxy)carbene precursor (1-acetoxy-1-propylidene) and the formation of two acyl chlorides supports the hypothesis that such a carbene can abstract Cl from CCl4, with subsequent β scission of the resulting radical. 1-Acetoxyethylidene was trapped with neat 2-acetoxypropene and with neat 2-methoxypropene to form cyclopropanes.
- Bekhazi, Michel,Warkentin, John
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p. 4870 - 4873
(2007/10/02)
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- Mechanism of the Direct Reaction of Phosphite Ozonides with Olefins
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The direct reaction of triphenyl phosphite ozonide (TPPO) with olefins, occurring at low temperatures where no thermal generation of singlet oxygen occurs, is observed in identical fashion with a caged-ring and two o-phenylene phosphite ozonides whose thermal generation of singlet oxygen is very slow compared to TPPO.Biadamantylidene, which is quite reactive toward singlet oxygen, appears totally hindered against the direct reaction with TPPO.In the case of Δ2-dihydropyran the direct reaction contrasts strongly with the behavior toward singlet oxygen in that (1) ene reaction is only one-tenth as great as dioxetane formation, (2) the importance of ene reaction is not a function of solvent polarity, and (3) ene reaction is inhibited by free-radical scavengers.In the case of tricyclopropylethylene, the formation of allylic hydroperoxides in the case of singlet oxygen is replaced in the direct TPPO reaction by cleavage to ketone and aldehyde under conditions where the hydroperoxides are stable and hence cannot be intermediates.The direct reaction of TPPO with 1,2-dimethylcyclohexene and 2-methyl-2-butene gave mixtures of ene products similar to those from singlet oxygen and, in the case of the former hydrocarbon, quite different from the product of chain oxidation.Dabco, tetramethyl-p-phenylenediamine, and other tertiary amines rapidly decompose phosphite ozonides to phosphate and ground-state oxygen, with evidence of electron transfer from the amines.In this and in the direct oxygenation of dihydropyran, the 31P NMR signal goes directly from 63 to 17 ppm, showing that there is no detectable intermediate state of phosphorus between TPPO and phosphate.The facts are accommodated by a mechanism involving initial bond formation between the olefin and thecenter oxygen atom of the ozonide, with chemical and sterochemical sequels which are discussed.The freezing point of chloroform is depressed to the same extent by TPPO as by triphenylphosphate, showing that TPPO is monomeric.
- Bartlett, Paul D.,Chu, Hsien-Kun
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p. 3000 - 3004
(2007/10/02)
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