Regio- and stereoselective co-iodination of olefins using NH4I and Oxone

A simple, efficient, and environmentally benign protocol for the synthesis of vicinal iodohydrins and iodoesters from olefins using NH₄I and Oxone in CH₃CN/H₂O (1:1) and dimethylformamide (DMF) / dimethylacetamide (DMA), respectively, without employing a catalyst at room temperature is described. Regio- and stereoselective iodohydroxylation and iodoesterification of various olefins with anti fashion, following Markonikov’s rule, was achieved and the corresponding products were obtained in good to excellent yields. In addition, 1,2-disubstituted olefins afforded excellent diastereoselectivity.     

Preparation and reactions of the (dicarbonyl)(η5-cyclopentadienyl)(tetrahydrofuran)iron cation: A convenient route to (dicarbonyl)(η5-cyclopentadiemyl)(η2-olefin)iron cations and related complexes

The versatile reagent [η⁵-C₅H₅)Fe(CO)₂(THF)]BF₄ has been isolated from the reaction of (η₅-C₅H₅)Fe(CO)₂I and AgBF₄ in THF and shown to react in CH₂Cl₂ with olefins to yield [(η⁵-C₅H₅)Fe(CO)₂(η²-olefin)]BF₄ complexes. For most olefins the yields are high. The yield in these reactions can be increased by treating the CH₂Cl₂ solution of [(η⁵-C₅H₅)Fe(Co)₂(THF)]BF₄ and olefin with gaseous BF₃ in order to complex the THF as the BF₃-THF adduct. Most striking is the increase in yield for the cyclohexene complex from 17% to 92%.     

An easy way for constructing hard-to-make epoxides employing HOF·CH3CN

HOF·CH₃CN, a very efficient oxygen transfer agent, was reacted with various types of difficult-to-epoxidize olefins. All products were obtained in a single-step, fast and high yield reaction.     

A simple PdCl2/O2/DMF catalytic system for highly regioselective cyclotrimerization of olefins with electron-withdrawing groups

A highly regioselective cyclotrimerization of olefins with electron-withdrawing groups in a PdCl₂/O₂/DMF catalytic system is disclosed, and a possible mechanism has also been proposed, which reveals the PdCl₂-catalyzed cyclotrimerization of olefins with electron-withdrawing groups goes through a quite different pathway from that of alkynes.     

Titanium-catalyzed hydrosilylation of olefins: A comparison study on Cp2TiCl2/Sm and Cp2TiCl2/LiAlH4 catalyst system

Hydrosilylation of olefins catalyzed by Cp₂TiCl₂/Sm (Cp?=?cyclopentadienyl) under solvent free conditions have been investigated. By using Cp₂TiCl₂/Sm as catalyst system, β-adducts and hydrogenation products were detected. Hydrosilylation of olefins catalyzed by Cp₂TiCl₂/LiAlH₄ under room temperature has also been studied. The influence of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) on Cp₂TiCl₂/Sm and Cp₂TiCl₂/LiAlH₄, respectively, indicated that hydrosilylation of olefins catalyzed with Cp₂TiCl₂/Sm went through a free radical reaction pathway while a coordination mechanism was applied for Cp₂TiCl₂/LiAlH₄ catalyst system.     

Microwave spectrum,structure and dipole moment of trimethylamine-borane

The ground state rotational spectra often isotopic species of trimethylamineborane, (CH₃)₃N¹⁰BH₃, (CH₃)₃N¹¹BH₃, (CH₃)₃N¹⁰BD₃, (CH₃)₃N¹¹BD₃, (CH₃)₃N¹¹BD₂H, (CD₃)₃N¹⁰BH₃, (CD₃)₃N¹¹BH₃, (CD₃)₃N¹⁰BD₃, (CD₃)₃N¹¹BD₃ and (¹³CH₃)(¹²CH₃)₂N¹¹BH₃, have been measured and the effective moments of inertia obtained. The utilization of Kraitchman's equations leads to an r_s value of the B-H distance of 1.211±0.003 Å and a NBH angle of 105.32±0.16°. By a least squares fit of the rotational constants the following structural parameters were obtained: r(NC) = 1.495 Å, r(BN) = 1.609 Å, and ∠BNC = 110.9°. The value of the dipole moment was found to be 4.59±0.13 D. A lower limit to the barrier to internal rotation of the BH₃ group was determined to be 3.4 kcal/mole.     

SN2-Selective allylic substitution of chiral γ-aryl substituted allylic picolinates with alkynylcopper reagents

Substitution of γ-aryl secondary allylic picolinates with alkynyl copper reagents was studied. The copper reagent, prepared from TMSCCMgBr and CuBr·Me₂S in 2:1, was subjected to substitution of the picolinate derived from (E)-3-phenyl-1-methyl-2-propenyl alcohol at 0 °C for 1 h in THF to produce a mixture of α- and γ-products and the alcohol in 67:20:13, while the reagent in 3 or 4:1 ratio gave the α-product with 90-91% selectivity. On the contrary, reaction in CH₂Cl₂-THF (6-8:1) at 0 °C for 1 h furnished the α-product with 99% regioselectivity. The effect of CH₂Cl₂ was also demonstrated with eight more examples. Furthermore, 99% inversion was determined by transformation to the literature compound and by chiral HPLC.     

CO Hydrogenation by K-Promoted Coprecipitated Co/Al2O3

Effect of K promotion on the CO hydrogenation activity and selectivity of coprecipitated Co/Al₂O₃ has been studied. K addition is found to lower total activity while enhancing C₂-C₄ olefins selectivity; kinetic data indicate that the reaction mechanism is not affected.     

Efficient Reduction of Aromatic Bis-Imides to Their Amine Derivatives

Excellent yields greater than 85% per carbonyl group were obtained during the reduction of aromatic bis-imides to the corresponding bis-amines with BH₃-THF complex.     

Reactivity of RuO species in RuO2/CeO2 catalysts prepared by a wet reduction method

The paper deals with the reactivity of RuO₂/CeO₂ prepared by a wet reduction method: ruthenium was supported on Ce(OH)₃, which was precipitated by alkali-hydrolysis of Ce(NO₃)₃, under a reduction condition with formaldehyde at pH 11 and transformed into RuO₂/CeO₂ catalysts by calcination in air at 773 K. The catalysts were investigated with an ESR technique and were tested for oxidation of propylene. They had no ESR signals by themselves at room temperature, but gave two sets of anisotropic signals upon contact with propylene. These signals were derived from the reaction products between RuO and propylene. The intensities of the signals were kept unchanged at room temperature for more than 1 h in the absence of excess propylene. The signals decayed in the presence of excess propylene and the upfield signal decayed more rapidly. A prior heating of the catalyst in air at 473 K or above caused the increase in the intensity of the upfield signal. The time course of the signal changes discriminated between ethylene and olefins with allylic hydrogen toward RuO species.     

Bromofluorination of olefins using BrF3; an efficient route for fluoroalkenes and fluoroamines

A variety of alkenes and α,β-unsaturated carbonyls were reacted with BrF₃ to form vicinal bromofluoro compounds. In most cases, the reactions followed a Markovnikov regioselectivity and anti-addition stereospecifity. They proceeded well even with deactivated olefins in around 70% yield. The bromofluoro compounds served as starting materials for the synthesis of fluoroalkenes and fluoroamines.     

Vibrational studies of BH−4 and BD−4 isolated in alkali halides

Single crystals of alkali halides doped with BH^?₄ and BD^?₄ were grown from the melt. Previously unreported bands in the infrared spectra of BH^?₄ and BD^?₄ isolated in different alkali halides are interpreted in terms of summation bands of internal and external modes of vibration. This has allowed the torsional and translational modes of the impurity ion to be identified. The tetrahedral symmetry of the borohydride ion is retained when it is isolated within alkali halides with the NaCl structure. A reduction of symmetry towards C_3v was observed when BH^?₄ (or BD^?₄) was isolated within lattices with CsCl structure.Raman and far infrared spectra of alkali halide/BH^?₄ systems will be reported for the first time, and high pressure infrared studies of these systems will be described. The effects of pressure in the internal mode, external modes, Fermi resonance and NaCl to CsCl structural phase changes will be discussed.     

A theoretical evaluation of steric and electronic effects on the structure of [OSO4 (NR3)] (NR3 = bulky chiral alkaloid derivative) complexes

Summary The novel theoretical scheme IMOMM, integrating ab initio and molecular mechanics contributions in a single geometry optimization process, is applied to the structural determination of different [OsO₄(NR₃)] (NR₃ = bulky chiral alkaloid derivative) species closely related to active catalysts for the asymmetric dihydroxylation of olefins. Computed values compare in a satisfactory way with available X-ray data, the relationship between the Os-N distance and the nature of the NR₃, ligand being properly reproduced. The computational scheme allows the separate quantification of electronic and steric effects, as well as the identification of the specific steric repulsions responsible for the difference.     

An Expedient Synthesis of Allylic/Secondary Bromides from Dehydration of Tertiary-β-bromo Alcohols

Abstract

Tertiary-β-bromo alcohols, derived from simple monoterpenes and olefins, react with BF₃.OEt₂ in refluxing benzene in 1–2 h to afford the corresponding allylic/secondary bromides in 45–90% yield. In case of substrates containing olefinic or hydroxyl groups, formation of cyclic ethers was observed.     

The allylic nucleophilic substitution of Morita-Baylis-Hillman acetates with isocyanides: a facile synthesis of trisubstituted olefins

Morita-Baylis-Hillman acetates undergo smooth allylic nucleophilic substitution (S_N2′) with tosylmethyl isocyanide (TosMIC) in the presence of a catalytic amount of BF₃·OEt₂ under mild conditions to furnish trisubstituted olefins in high yields with (E)-stereoselectivity.     

ZrCdOx/SAPO-18双功能催化剂催化CO2加氢合成低碳烯烃性能

采用并流共沉淀法制备了不同Zr/Cd原子比(n_Zr/n_Cd)的ZrCdO_x金属氧化物,并与水热法制备的不同硅铝比(n_{SiO_(2})/n_{Al_(2}O₃))的片状SAPO-18分子筛物理混合制得ZrCdO_x/SAPO-18双功能催化剂,研究了其催化CO₂加氢直接合成低碳烯烃性能。采用透射电子显微镜(TEM)、X射线衍射(XRD)、N2吸附-脱附、CO₂程序升温脱附(CO₂-TPD)、NH3程序升温脱附(NH3-TPD)和X射线光电子能谱(XPS)对催化剂进行了分析。与单一ZrO2相比,引入CdO使得ZrCdO_x比表面积下降,当n_Zr/n_Cd=8时制备的Zr8Cd1氧化物呈现出无定形小颗粒状,Zr与Cd之间较强的协同作用使得Zr Cd Ox氧化物产生了更多的氧空位,有利于CO₂的吸附活化。通过对Zr8Cd1金属氧化物与SAPO-18(硅铝比0.1)的质量比、工艺反应温度、压力和空速对催化性能影响的考察,获得了最佳反应条件。研究还发现,当SAPO-18的硅铝比从0.1降为0.01时,Br?nsted酸含量降低,产物中烯烃/烷烃物质的量之比从18.6提高至37.2,但副产物CO含量迅速增加,低碳烯烃时空收率明显下降。     

ZrCdOx/SAPO-18双功能催化剂催化CO2加氢合成低碳烯烃性能

采用并流共沉淀法制备了不同Zr/Cd原子比（n_Zr/n_Cd）的ZrCdO_x金属氧化物，并与水热法制备的不同硅铝比（n_SiO2/n_{Al2O3）的片状SAPO-18分子筛物理混合制得ZrCdOx/SAPO-18双功能催化剂，研究了其催化CO2加氢直接合成低碳烯烃性能。采用透射电子显微镜（TEM）、X射线衍射（XRD）、N2吸附-脱附、CO2程序升温脱附（CO2-TPD）、NH3程序升温脱附（NH3-TPD）和X射线光电子能谱（XPS）对催化剂进行了分析。与单一ZrO2相比，引入CdO使得ZrCdOx比表面积下降，当nZr/nCd=8时制备的Zr8Cd1氧化物呈现出无定形小颗粒状，Zr与Cd之间较强的协同作用使得ZrCdOx氧化物产生了更多的氧空位，有利于CO2的吸附活化。通过对Zr8Cd1金属氧化物与SAPO-18（硅铝比0.1）的质量比、工艺反应温度、压力和空速对催化性能影响的考察，获得了最佳反应条件。研究还发现，当SAPO-18的硅铝比从0.1降为0.01时，Brø；nsted酸含量降低，产物中烯烃/烷烃物质的量之比从18.6提高至37.2，但副产物CO含量迅速增加，低碳烯烃时空收率明显下降。}     

Conjugate addition of indoles and thiols with electron-deficient olefins catalyzed by Bi(OTf)3

Conjugate addition of indoles and thiols with a variety of electron-deficient olefins mediated by a catalytic amount of Bi(OTf)₃ at ambient temperature to afford the corresponding Michael adducts in good to excellent yields with high selectivity is reported.     

The electrophilic addition of thiols to olefins: A theoretical and experimental study

Density functional theory with the B3LYP hybrid functional and 6–31G* basis set was used to study the geometric and electronic structure of H₂C = CHR (R = H, CH₃, C₂H₅, C₃H₇, C₄H₉, and C₅H₁₁) olefins, their carbocations formed in the addition of the proton to the olefins, R′-S-H aliphatic thiols (R′ = H, CH₃, C₂H₅, and C₃H₇), the products of the addition of thiols to carbocations, and the final products of the addition of thiols to olefins. The proton affinity of the olefins and the products of the addition of thiols to olefins was calculated. The conclusion was drawn that the limiting stage in the nonradical addition of thiols to olefins catalyzed by acids was proton transfer from the protonated reaction product to the olefin. The theoretical results were compared with the experimental data on the electrophilic addition of polymercaptan to heptene-1.     

Organometallic consequences of a redox reaction: Terminal trimethylsilylmethylidene titanium complexes prepared by a one-electron oxidation step

One-electron oxidation of the titanium(III) bis-trimethylsilylmethyl complex (nacnac)Ti(CH₂SiMe₃)₂ (1) (nacnac⁻ = [ArNC(Me)]₂CH, Ar = 2,6-ⁱPr₂C₆H₃), readily prepared from (nacnac)TiCl₂(THF) and 2 equiv. of LiCH₂SiMe₃ in Et₂O, with AgOTf results in formation of the five-coordinate and terminal titanium alkylidene complex (nacnac)TiCHSiMe₃(OTf)(THF) (2)-THF concurrent with extrusion of tetramethylsilane and precipitation of silver metal. Complex 2-THF eliminates THF slowly under dynamic vacuum to generate the four-coordinate alkylidene 2 along with some decomposition products. Alternatively, the four-coordinate and non-solvento alkylidene complex, 2, can be prepared from 1 and AgOTf in pentane. Complex 2 undergoes cross-metathesis transformation to afford [ArNC(Me)CHC(Me)CHSiMe₃]TiNAr(OTf) (3) as the major product after 34 h at room temperature. Complexes 1, 2, 2-THF, and 3 have been fully characterized spectroscopically, and single crystal X-ray diffraction analysis for 1 and 2-THF are presented.