MP2, CCSD(T), and Density Functional Theory Study of the 2‑Butyl Cation: New Insight into the Methyl- and Hydrogen-Bridged Structures

Using the MP2, CCSD­(T), and DFT (B3LYP) methods, the structures and energies of the 2-butyl cation (C₄H₉⁺) were calculated. Energetically, the C–C hyperconjugated structure <b>1</b> and hydrogen-bridged structure <b>2</b> were found to be almost identical at all levels. The ¹³C NMR chemical shifts of <b>1</b> and <b>2</b> were computed by the GIAO-CCSD­(T) method using different geometries. On the basis of calculated relative energies and calculated ¹³C NMR chemical shifts, an equilibrium involving <b>1</b> and <b>2</b> (in a 50:50 ratio) seemed likely responsible for the experimentally observed ¹³C NMR chemical shifts in superacid solutions at −80 °C. However, on the basis of computed and experimental frequencies the hydrogen-bridged structure <b>2</b> is most likely responsible for the experimentally observed frequencies in the solid state at −125 °C

Comparative Study of Alkane Dications (Protonated Alkyl Cations, C_<i>n</i>H_2<i>n</i>+2²⁺) and Their Isoelectronic Boron Cation Analogues

Comparative study of the superelectrophilic alkane dications (C_<i>n</i>H_2<i>n</i>+2²⁺, <i>n</i> = 1–5) and their isoelectronic boron cation analogues was carried out using the ab initio method at the MP2/cc-pVTZ level. The structure, bonding, and relative stability of doubly charged alkane dications and monocharged boron cation analogues are discussed. These studies contribute to our general understanding of the superelectrophilic activation of alkyl cations as well as the electrophilic reactivity of C–H and C–C single bonds

Bi-reforming of Methane from Any Source with Steam and Carbon Dioxide Exclusively to Metgas (CO–2H₂) for Methanol and Hydrocarbon Synthesis

A catalyst based on nickel oxide on magnesium oxide (NiO/MgO) thermally activated under hydrogen is effective for the bi-reforming with steam and CO₂ (combined steam and dry reforming) of methane as well as natural gas in a tubular flow reactor at elevated pressures (5–30 atm) and temperatures (800–950 °C). By adjusting the CO₂-to-steam ratio in the gas feed, the H₂/CO ratio in the produced syn-gas could be easily adjusted in a single step to the desired value of 2 for methanol and hydrocarbon synthesis

Nucleophilic Trifluoromethylation of Carbonyl Compounds: Trifluoroacetaldehyde Hydrate as a Trifluoromethyl Source

A feasible nucleophilic trifluoromethylating protocol has been developed using trifluoroacetaldehyde hydrate as an atom-economical trifluoromethyl source. The reaction was found to be applicable to the nucleophilic trifluoromethylation of a broad spectrum of carbonyl compounds with satisfactory yields in general. DFT calculations have been performed to provide mechanistic insight into the present and related reactions employing 2,2,2-trifluoro-1-methoxyethanol and hexafluoroacetone hydrate

Conversion of CO₂ from Air into Methanol Using a Polyamine and a Homogeneous Ruthenium Catalyst

A highly efficient homogeneous catalyst system for the production of CH₃OH from CO₂ using pentaethylenehexamine and Ru-Macho-BH (<b>1</b>) at 125–165 °C in an ethereal solvent has been developed (initial turnover frequency = 70 h^–1 at 145 °C). Ease of separation of CH₃OH is demonstrated by simple distillation from the reaction mixture. The robustness of the catalytic system was shown by recycling the catalyst over five runs without significant loss of activity (turnover number > 2000). Various sources of CO₂ can be used for this reaction including air, despite its low CO₂ concentration (400 ppm). For the first time, we have demonstrated that CO₂ captured from air can be directly converted to CH₃OH in 79% yield using a homogeneous catalytic system

Enantioselective Synthesis of α-Stereogenic γ-Keto Esters via Formal Umpolung

A feasible method has been developed for the enantioselective synthesis of α-stereogenic γ-keto esters. By employing nitro(phenylsulfonyl)methane as an acyl anion equivalent, the integrated Michael addition reaction-oxidative methanolysis protocol allows the preparation of various γ-keto esters with high optical purities

A Domino Approach of Heck Coupling for the Synthesis of β-Trifluoromethylstyrenes

A domino approach of Heck coupling was used to synthesize β-trifluoromethylstyrene derivatives from iodoarenes and 1-iodo-3,3,3-trifluoropropane in moderate to good yields. This method avoids the use of low-boiling, gaseous reagents such as 3,3,3-trifluoropropene, and additives and phosphines in the catalytic system

Efficient Reversible Hydrogen Carrier System Based on Amine Reforming of Methanol

A novel hydrogen storage system based on the hydrogen release from catalytic dehydrogenative coupling of methanol and 1,2-diamine is demonstrated. The products of this reaction, <i>N</i>-formamide and <i>N</i>,<i>N</i>′-diformamide, are hydrogenated back to the free amine and methanol by a simple hydrogen pressure swing. Thus, an efficient one-pot hydrogen carrier system has been developed. The H₂ generating step can be termed as “amine reforming of methanol” in analogy to the traditional steam reforming. It acts as a clean source of hydrogen without concurrent production of CO₂ (unlike steam reforming) or CO (by complete methanol dehydrogenation). Therefore, a carbon neutral cycle is essentially achieved where no carbon capture is necessary as the carbon is trapped in the form of formamide (or urea in the case of primary amine). In theory, a hydrogen storage capacity as high as 6.6 wt % is achievable. Dehydrogenative coupling and the subsequent amide hydrogenation proceed with good yields (90% and >95% respectively, with methanol and <i>N</i>,<i>N</i>′-dimethylethylenediamine as dehydrogenative coupling partners)

<i>N</i>‑Difluoromethylation of Imidazoles and Benzimidazoles Using the Ruppert–Prakash Reagent under Neutral Conditions

Direct <i>N</i>-difluoromethylation of imidazoles and benzimidazoles has been achieved using TMS-CF₃ (the Ruppert–Prakash reagent) under neutral conditions. Difluoromethylated products were obtained in good-to-excellent yields. Inexpensive, commercially available starting materials, neutral conditions, and shorter reaction times are advantages of this methodology. Reactions are accessible through conventional as well as microwave irradiation conditions

Single Step Bi-reforming and Oxidative Bi-reforming of Methane (Natural Gas) with Steam and Carbon Dioxide to Metgas (CO-2H₂) for Methanol Synthesis: Self-Sufficient Effective and Exclusive Oxygenation of Methane to Methanol with Oxygen

Catalysts based on suitable metal oxide supports, such as NiO/MgO and CoO/MgO, were shown to be active for single step bi-reforming, the combined steam and dry reforming of methane or natural gas with H₂O and CO₂ exclusively to metgas (CO-2H₂) for efficient methanol synthesis. Reactions were carried out in a tubular flow reactor under pressures up to 42 bar at 830–910 °C. Using a CH₄ to steam to CO₂ ratio of ∼3:2:1 in the gas feed, the H₂/CO ratio of 2:1 was achieved, which is desired for subsequent methanol synthesis. The needed 2/1 steam/CO₂ feed ratio together with the reaction heat for the endothermic bi-reforming can be conveniently obtained by the complete combustion of a quarter part of the overall used methane (natural gas) with oxygen of the air (oxidative bi-reforming). Complete combustion of a part of methane followed by bi-reforming leads to the production of metgas (H₂/CO in 2:1 mol ratio) for self-sufficient exclusive methanol synthesis. The long sought after but elusive efficient and selective oxygenation of methane to methanol is thus achieved in an effective and economic way without any oxidation byproduct formation according to CH₄ + 1/2O₂ → CH₃OH