DMSO/N2H4.H2O/I2/H2O/CH3CN: a new system for selective oxidation of alcohols in hydrated media

A new alternative system for the oxidation of secondary alcohols to ketones with DMSO/N2H4.H2O/I2/H2O/CH3CN in hydrated media has been developed. The system also selectively oxidizes the secondary alcoholic groups to the corresponding ketones in the presence of primary alcoholic groups present within the same molecule in moderate to very good yields at reflux temperature.     

Enantioselective hydrogenation of aromatic ketones catalyzed by Ru complexes of Goodwin-Lions-type sp2N/sp3N hybrid ligands R-BINAN-R'-Py

Goodwin-Lions-type sp2N/sp3N hybrid ligands R-BINAN-R'-Py possessing a C2 axis binaphthyl skeleton have been designed and synthesized. Combination of the new non-phosphine ligand with Ru(pi-CH2C(CH3)CH2)2(cod) has been revealed to catalyze the hydrogenation of aromatic ketones with high enantioselectivity of up to 99% ee. The reaction proceeds essentially without the need for any bases, but the reactivity is enhanced by the addition of KOt-C4H9 attaining an S/C ratio of up to 10 000. The success should expand the range of possibilities in designing catalysts not only for hydrogenation but also for many other reactions.     

A general access to 1,1-cyclopropane aminoketones and their conversion into 2-benzoyl quinolines

1,1-Cyclopropane aminoketones were efficiently synthesized in high yields by the tandem reaction of α-amino aryl ketones with vinyl sulfonium salts using DBU as the base in CH(2)Cl(2). This methodology was utilized to synthesize 2-benzoyl quinolines.     

New, general, and practical preparation of methyl ketones via the direct coupling of amides with CH2Cl2 promoted by TiCl4/Mg

The direct coupling of a variety of amides with CH2 Cl2 or CD2 Cl2 promoted by TiCl 4/Mg/THF provides an extremely simple, practical, selective, and efficient approach for the construction of methyl ketones. The efficiency and practicability of this chemistry is illustrated by the very simple synthesis of deuterated methyl ketones.     

Intramolecular reactions of benzylic azides with ketones: competition between Schmidt and Mannich pathways.

The Lewis acid-promoted reactions of benzylic azides with ketones can proceed by two major pathways. The azido-Schmidt reaction involves simple addition of azide to the ketone followed by rearrangement and ring expansion. In addition, benzylic azides can undergo prior rearrangement to afford iminium ions that can subsequently participate in a Mannich reaction. A series of ketones containing an alpha CH2(CH2)nCH(N3)Ph substituent (n = 1-3) was prepared to investigate the dependence of products on ketone ring size and tether length. For all ketones examined, good yields of bicyclic lactams arising from intramolecular Schmidt reaction were obtained when a four-carbon linker was used (n = 1 in the above formulation), but Mannich products predominated for the longer tethers examined (n = 2, 3).     

Direct electrophilic diamination of functionalized alkenes without the use of any metal catalysts

A new direct electrophilic diamination reaction of alpha,beta-unsaturated ketones and esters has been established without the use of any metal catalysts. Three types of nitriles (CH(3)CN, CH(3)CH(2)CN, and CH(3)CH(2)CH(2)CN) were employed as nucleophilic nitrogen sources. A new mechanism has also been proposed to explain the resulting regio- and stereoselectivity.     

Expeditious copper-catalyzed conjugate 1,4-addition of bromo[2-(1,3-dioxolan-2-yl)ethyl]magnesium to alpha,beta-cycloalkenones and subsequent transformations

Expeditious CuI-catalyzed conjugate 1,4-addition of bromo[2-(1,3-dioxolan-2-yl)ethyl]magnesium to the five-, six-, seven-, and eight-membered alpha,beta-cycloalkenones is described. The reaction times are decreased dramatically compared to CuBr-(CH(3))(2)S catalysis. The resulting ketoacetals were subsequently cyclized to bicyclic beta-hydroxy ketones and alpha,beta-enones, followed by further transformations.     

CH3NO2和CH3自由基吸氢反应途径和变分速率常数计算

采用MP2(full)/6-311G(d, p)从头算方法,优化了硝基甲烷和甲基自由基吸氢反应的过渡态结构,经QCISD(T)方法进行能量校正,得出该反应的正逆向反应的活化位垒分别是58.21 kJ•mol－1和67.17 kJ•mol－1.沿IRC分析指出该反应是氢转移协同反应,而且在反应途径上存在一个引导反应进行的振动模式,这一反应模式引导反应进行的区间在反应坐标S的-0.9～1.0(amu)1/2bohr之间;在温度为800～2600 K范围内,运用改进的变分过渡态理论(ICVT),计算了该反应的速率常数,并与实验类比所得的速率常数随温度的变化趋势进行了比较.     

Reactions of silica chloride (SiO(2)Cl)/DMSO, a heterogeneous system for the facile regeneration of carbonyl compounds from thioacetals and ring-expansion annelation of cyclic thioacetals

Silica chloride (SiO(2)Cl)/DMSO, as a heterogeneous system, has been efficiently used for deprotection of thioacetals into aldehydes in dry CH(2)Cl(2) at room temperature. Thioketals without enolizable hydrogens adjacent to a sulfur atom are converted easily to the corresponding ketones in high yields under similar reaction conditions. However, thioketals with enolizable methyl and methylene groups undergo ring-expansion reactions to afford 1,4-dithiepins and 1,4-dithiins in dry CH(2)Cl(2) at room temperature in good yields.     

Study of the reaction of 1,1-bis(trimethylsilyl)-2-phenylethylene with some acyl chlorides in the presence of AlCl3

1,1-Bis(trimethylsilyl)-2-phenylethylene (1), which has been synthesized from the Peterson reaction between (Me₃Si)₃CLi and benzaldehyde, reacts with various acyl chlorides (RCOCl, R = Me, Et, iso-Pr, n-Bu, iso-Bu, iso-C₅H₁₁, PhCH₂, PhCH₂CH₂) in the presence of AlCl₃ to give -silyl-,β-unsaturated enones 3a–3h with high E stereoselectivity along with trans-,β-unsaturated ketones 4a–4h. The enones 3 can be partially converted into the ketones 4 with an excess of AlCl₃. Reaction of 1 with RCOCl, (R = Ph, CH₃CH=CH) afforded only the ketones 4. Yields were dependent on time and the amounts of AlCl₃ used.     

Removal of NO in NO/N2, NO/N2/O2, NO/CH4/N2, and NO/CH4/O2/N2 systems by flowing microwave discharges

In this paper, continuing previous work, we report on experiments carried out to investigate the removal of NO from simulated flue gas in nonthermal plasmas. The plasma-induced decomposition of small concentrations of NO in N2 used as the carrier gas and O2 and CH4 as minority components has been studied in a surface wave discharge induced with a surfatron launcher. The reaction products and efficiency have been monitored by mass spectrometry as a function of the composition of the mixture. NO is effectively decomposed into N2 and O2 even in the presence of O2, provided always that enough CH4 is also present in the mixture. Other majority products of the plasma reactions under these conditions are NH3, CO, and H2. In the absence of O2, decomposition of NO also occurs, although in that case HCN accompanies the other reaction products as a majority component. The plasma for the different reaction mixtures has been characterized by optical emission spectroscopy. Intermediate excited species of NO*, C*, CN*, NH*, and CH* have been monitored depending on the gas mixture. The type of species detected and their evolution with the gas composition are in agreement with the reaction products detected in each case. The observations by mass spectrometry and optical emission spectroscopy are in agreement with the kinetic reaction models available in literature for simple plasma reactions in simple reaction mixtures.     

The hydrogenation/transfer hydrogenation network: asymmetric hydrogenation of ketones with chiral eta6-arene/N-Tosylethylenediamine-ruthenium(II) catalysts

Chiral eta6-arene/N-tosylethylenediamine-Ru(II) complexes, known as excellent catalysts for asymmetric transfer hydrogenation of aromatic ketones in basic 2-propanol, can be used for asymmetric hydrogenation using H2 gas. Active catalysts are generated from RuCl[(S,S)-TsNCH(C6H5)CH(C6H5)NH2](eta6-p-cymene) in methanol, but not 2-propanol, or by combination of Ru[(S,S)-TsNCH(C6H5)CH(C6H5)NH](eta6-p-cymene) and CF3SO3H or other non-nucleophilic acids. This method allows, for the first time, asymmetric hydrogenation of simple ketones under acidic conditions. Hydrogenation of base-sensitive 4-chromanone and its derivatives with the S,S catalyst proceeds in methanol with a substrate-to-catalyst molar ratio of 1000-3000 (10 atm) to 7000 (100 atm), giving (S)-4-chromanols with 97% ee quantitatively. The reaction can be achieved even on a 2.4 kg scale. The mechanistic rationale for the catalytic efficiency is presented.     

Thermochemistry and accurate quantum reaction rate calculations for H2/HD/D2 + CH3

Accurate quantum-mechanical results for thermodynamic data, cumulative reaction probabilities (for J = 0), thermal rate constants, and kinetic isotope effects for the three isotopic reactions H2 + CH3 --> CH4 + H, HD + CH3 --> CH4 + D, and D2 + CH3 --> CH(3)D + D are presented. The calculations are performed using flux correlation functions and the multiconfigurational time-dependent Hartree (MCTDH) method to propagate wave packets employing a Shephard interpolated potential energy surface based on high-level ab initio calculations. The calculated exothermicity for the H2 + CH3 --> CH4 + H reaction agrees to within 0.2 kcal/mol with experimentally deduced values. For the H2 + CH3 --> CH4 + H and D2 + CH3 --> CH(3)D + D reactions, experimental rate constants from several groups are available. In comparing to these, we typically find agreement to within a factor of 2 or better. The kinetic isotope effect for the rate of the H2 + CH3 --> CH4 + H reaction compared to those for the HD + CH3 --> CH4 + D and D2 + CH3 --> CH(3)D + D reactions agree with experimental results to within 25% for all data points. Transition state theory is found to predict the kinetic isotope effect accurately when the mass of the transferred atom is unchanged. On the other hand, if the mass of the transferred atom differs between the isotopic reactions, transition state theory fails in the low-temperature regime (T < 400 K), due to the neglect of the tunneling effect.     

硼氢化三苯基苄基磷的制备及还原性研究

用苄基三苯基氯化磷与硼氢化钠反应制备硼氢化三苯基苄基磷(简写BTPBP),还原醛、酮和酰氯等羰基化合物为相应的醇,具有良好的还原选择性的较好的产率并探讨了其反应过程。     

A novel photochromic system of 4,5-dialkenylthiophenes constructed by the smarium diiodide promoted coupling reactions of thiophene-2-carboxylate with aryl ketones

[reaction: see text] The SmI2-promoted coupling reaction of ethyl thiophene-2-carboxylate with aryl ketones (2 equiv), followed by acid-catalyzed dehydration and oxidative aromatization, gave dialkenylthiophenes 1b-d, which underwent electrocyclizations upon irradiation with 300-nm light in CH3CN solution to give the corresponding closed-ring species with absorption lambda(max) approximately 425 nm. The interconversion between dialkenylthiophenes and their corresponding closed-ring species constitutes a novel photochromic system bearing an ester group for potential uses in linkage and wavelength tuning.     

Gas-phase halonium metathesis and its competitors. Skeletal rearrangements of cationic adducts of saturated ketones

The methyl cation and CF(3)(+) attack saturated, acyclic ketones to make vibrationally excited adduct ions. Despite their high internal energies and short lifetimes, these adducts undergo deep-seated rearrangements that parallel slower processes in solution. Observed pathways include alkene and alkane expulsions, in addition to (in the case of CF(3)(+)) the precedented loss of CF(2)O + HF. For the vast majority of ketones, the principal charged products are the CF(3)(+) adducts of lighter carbonyl compounds, ions that are not easily prepared by other avenues. Evidence for ion structures comes from collisionally activated unimolecular decomposition and bimolecular ion-molecule reactions. Typical examples are di-n-propyl and diisopropyl ketones (both of which produce CH(3)CH=OCF(3)(+) as the principal ion-molecule reaction product) and pentamethylacetone (which produces (CH(3))(2)C=OCF(3)(+) as virtually the sole ion-molecule reaction product). Isotopic labeling experiments account for mechanisms, and DFT calculations provide a qualitative explanation for the relative abundances of products from unimolecular decompositions of the chemically activated CF(3)(+) adduct ions that are initially formed.     

均相苯乙酮加氢反应研究

合成了一种新的钌膦配合物[RuCl2(Dmpp)2en](Dmpp=4-(2，6-二甲氧吡啶基)二苯基膦，en=乙二胺)，对其结构进行了表征．系统研究了反应温度，氢气压力，底物和催化剂的比例，碱和催化剂的比例等反应条件对[RuCl2(Dmpp)2en]催化的芳香酮加氢反应活性的影响，证明其在苯乙酮加氢反应中具有很好的催化活性．     

甲烷-空气-H2O模拟光化学反应体系中CH3OO·自身复合反 应的研究

在1.013×10^5Pa,(298±2)K及O2-N2气氛下,研究了羟基自由基·OH引发的甲烷光化学反应体系中过氧甲基自由基CH3OO·自身复合反应。反应物和产物采用长光路Fourier红外光谱(LP-FTIR)和高效液相色谱(HPLC)测定。证实产物中有甲基过氧化氢(CH3OOH,MHP)和过氧甲醚(CH3OOCH3,DMP)存在并首次在该体系中发现了羟甲基过氧化氢(HOCH2OOH,HMHP).HMHP的检出表明,CH3OO·自身复合的可能途径之一生成了Criegee中间体过氧次甲基双自由基·CH2OO·,采用G2,G2(MP2)和G2(ful)方法对一些反应的标准焓变和标准Gibbs自由能变化进行了理论计算。结果表明CH3OO·自身复合生成·CH2OO·及·CH2OO·与H2O反应生成HMHP的途径在热力学上是可能的。     

1-Trifluoromethyl-2-chloroethylthiolated carbonyl compounds: Synthesis and properties

1-Trifluoromethyl-2-chloroethylsulfenyl chloride thiolates enolizible ketones, forming products of mono- and disubstitution. The properties of the resultant sulfides are determined by the presence in the molecule of two acidic CH centers. Thus, bromination proceeds at the ambident center and reaction with bases leads to (1-trifluoromethylvinyl) sulfides which are able to undergo intramolecular cyclizations and Diels-Alder reactions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 676–681, March, 1991.     

Reactions of aliphatic ketones R2CO (R=Me, Et, iPr and tBu) with the MCI4/Li(Hg) system (M=U or Ti): mechanistic analogies between the McMurry, Wittig, and Clemmensen reactions

Analysis of the products of the reactions of ketones R2CO (R = Me, Et, iPr, tBu) with the MCl4/Li(Hg) system (M = U, Ti) at 20 degrees C revealed significant differences. For R = Me, the reaction proceeded exclusively (M = U) or preferentially (M = Ti) via a metallopinacol intermediate resulting from dimerization of ketyl radicals. Pinacol was liberated by hydrolysis, and tetramethylethylene was obtained after further reduction at 65 degrees C. For R=iPr, formation of iPr2C=CiPr2 as the only coupling product, the nonproduction of this alkene by reduction of the uranium pinacolate [U]-OCR2CR2O-[U] (R= iPr) at 20 degrees C, and the instability of the corresponding titanium pinacolate towards rupture of the pinacolic C-C bond indicated that reductive coupling of iPr2CO did not proceed by dimerization of ketyl radicals. Formation of 2,4-dimethyl-2-pentene was in favor of a carbenoid intermediate resulting from deoxygenative reduction of the ketyl. These results revealed that for sterically hindered ketones, McMurry reactions can be viewed as Wittig-like olefination reactions. For R=tBu, no coupling product was obtained and the alkane tBu2CH2 was the major product. The involvement of the carbenoid species [M]=CtBu2 was confirmed by its trapping with H2O, leading to tBu2CH2, and with the aldehydes RCHO, giving the cross-coupling products tBu2C=C(R)H (R = Me, tBu). Therefore, in the case of severely congested ketones, McMurry reactions present strong similarities to the Clemmensen reduction of ketones, owing to the involvement in both reactions of carbenoid species which exhibit similar reactivity.