•Triethoxysilylpropoxy-functionalized Shvo's catalyst precursors were immobilized on silica by covalent anchoring and sol-gel methods.•The immobilized Shvo's catalyst precursors were used for the transfer hydrogenation of levulinic acid with formic acid.•Hot filtration tests showed no leaching of the immobilized Shvo's catalysts.Two triethoxysilylpropoxy-functionalized Shvo's catalyst precursors were synthesized and characterized by IR, NMR and HRMS. Both covalent anchoring and sol-gel methods were used for their immobilization. The homogeneous and immobilized catalysts were used for the transfer hydrogenation of levulinic acid with formic acid to form hydroxyvaleric acid, which was readily dehydrated to yield gamma-valerolactone. The immobilized catalysts prepared by the sol-gel method showed higher activity than the covalently grafted catalysts. Hot filtration tests showed no leaching of the immobilized Shvo's catalysts, opening the door to facile catalyst recycling.Download high-res image (127KB)Download full-size image

Dry gamma-valerolactone (GVL) is stable for several weeks at 150 °C and its thermal decomposition only proceeds in the presence of appropriate catalysts. Since GVL does not react with water up to 60 °C for several weeks, it could be used as a green solvent at mild conditions. At higher temperatures, GVL reacts with water to form 4-hydroxyvaleric acid (4-HVA) and reaches the equilibrium in a few days at 100 °C. Aqueous solutions of acids (HCl and H2SO4) catalyze the ring opening of GVL even at room temperature, which leads to the establishment of an equilibrium between GVL, water, and 4-HVA. Although the 4-HVA concentration would be below 4 mol% in the presence of acids, it could be higher than the concentration of a reagent or a catalyst precursor, not to mention a catalytically active species. The latter could be especially worrisome as 4-HVA could be an excellent bi- or even a tri-dentate ligand for transition metals. Aqueous solution of bases (NaOH and NH4OH) also catalyzes the reversible ring opening of GVL. While in the case of NaOH, the product is the sodium salt of 4-hydroxyvalerate, the reversible reaction of GVL, with NH4OH results in the formation of 4-hydroxyvaleric amide. The reversible ring opening of (S)-GVL in the presence of HCl or NaOH has no effect on the stability of the chiral center.

The application of biomass-based resources for the production of chemicals could slow the depletion rate of fossil reserves and enable the development of a sustainable chemical industry. Three sustainability metrics, the sustainability value of resource replacement (SVrep), the sustainability value of the fate of waste (SVwaste), and the sustainability indicator (SUSind), were defined for biomass-based carbon chemicals by using the ethanol equivalent (EE) as a common currency. These sustainability metrics were calculated for ethylene, propylene, toluene, p-xylene, styrene, and ethylene oxide in the U.S.A. for 2008 and 2014. Our calculations are based on the initial chemical dehydration of corn-ethanol to ethylene followed by its conversion by existing chemical processes. These basic chemicals cannot be produced sustainably at this time primarily due to the limited availability of bioethanol. Consequently, bioethanol-based carbon products should only be labeled “sustainable” when the necessary biomass is available to produce the required bioethanol, independently of social and economic changes. The waste management of the processes shows much better sustainability values than the resource management, due to the successful greening of petrochemical processes.Keywords: Biomass-based basic chemicals; Ethanol equivalent; Metrics; Sustainability;

Fluorous ethers, having one or more fluorous ponytails containing longer and shorter F(CxF2x)-perfluoroalkyl substituent(s) where x ≥ 6 or x = 1–5, respectively, were reviewed including some of their basic properties, synthesis and selected applications in chemical processes.

The sulfuric acid-catalyzed conversion of paper wastes in gamma-valerolactone (GVL) or dioxane leads to the formation of levulinic acid (LA) and formic acid (FA), which can be converted to GVL by transfer-hydrogenation using the Shvo catalyst in situ or separately. The isolation of LA and FA was assisted by the neutralization of the sulfuric acid with ammonia to form a biphasic system. While the ammonium sulfate and most of FA and some of LA were in the aqueous phase, the organic solvent-rich phase contained most of the LA and some of the FA. GVL was used as an illuminating liquid in glass lamps for hours without the formation of noticeable smoke and/or odor even in a small room. While neat GVL can be used for the safe but somewhat slow lighting of charcoal, the ignition with different mixtures of GVL (95 or 90 vol %) and ethanol (5 or 10 vol %) was reduced to a convenient few seconds. Ignition tests of charcoal combined with emission analyses revealed that by increasing the ethanol content to 10 vol % the relative VOC emission can be decreased by 15% compared to the commercial lighter fluids.Keywords: Ethanol; Gamma-valerolactone; Illuminating liquids; Lighter fluids; Paper wastes;

The conversion of fructose, glucose, and sucrose to 5-(hydroxymethyl)furfural (HMF) and levulinic acid (LA)/formic acid (FA) was investigated in detail using sulfuric acid as the catalyst and γ-valerolactone (GVL) as a green solvent. The H2SO4/GVL/H2O system can be tuned to produce either HMF or LA/FA by changing the acid concentration and thus allowing selective switching between the products. Although the best yields of HMF were around 75%, the LA/FA yields ranged from 50% to 70%, depending on the structure of the carbohydrates and the reaction parameters, including temperature, acid, and carbohydrate concentrations. While the conversion of fructose is much faster than glucose, sucrose behaves like a 1:1 mixture of fructose and glucose, indicating facile hydrolysis of the glycosidic bond in sucrose. The mechanism of the conversion of glucose to HMF or LA/FA in GVL involves three intermediates: 1,6-anhydro-β-d-glucofuranose, 1,6-anhydro-β-d-glucopyranose, and levoglucosenone.Keywords: 5-(hydroxymethyl)furfural; carbohydrates; formic acid; isotopic labeling; levulinic acid; sulfuric acid; γ-valerolactone

The selective transfer hydrogenation of levulinic acid (LA) with formic acid (FA) to 4-hydroxyvaleric acid (4-HVA) and carbon dioxide followed by the intramolecular dehydration of 4-HVA to γ-valerolactone (GVL) are key steps of the conversion of carbohydrate-based biomass to GVL, which can be used for the production of both energy and carbon-based products. LA was converted to GVL in the presence of a small excess of FA and the Shvo catalysts {[2,5-Ph2-3,4-(Ar)2(η5-C4CO)]2H}Ru2(CO)4(μ-H)]} (Ar = p-MeOPh (1a), p-MePh (1b), Ph (1c)). The reactions were performed at 100 °C with yields higher than 99% after a few hours. The formation of 1,4-pentanediol and 2-methyltetrahydrofuran remained below detection limits. The only side products were water and carbon dioxide, as expected, which were easily removed and separated from the product GVL under reduced pressure. The Shvo catalyst 1c was recycled four times without losing catalytic activity, and the product GVL was isolated each time as a colorless liquid of 99.9% purity with only trace amounts of water present.

The hydroformylation of octene-1 and the removal of Co2(CO)8 and HCo(CO)4 from the reaction products including commercial C9 OXO-product were studied under biphasic conditions using an aqueous solution of different electron-donating sulfonated phosphine RnP(C6H4-m-SO3Na)2 (n = 0, 1, 2; R = Me, Bu, Cp) ligands. Depending on the electronic and steric properties of the phosphines, 6–70 ppm residual cobalt concentrations could be achieved in the organic phase under 10 bar of CO/H2 (1:1) at 75 °C. The formation of several water-soluble-phosphine-substituted cobalt carbonyl species including Co2(CO)6(TPPTS)2, HCo(CO)3(TPPTS), HCo(CO)2(TPPTS)2, and [Co(CO)3(TPPTS)2]+[Co(CO)4]− were identified and monitored by in situ IR and NMR spectroscopy.

The one-pot conversion of fructose to γ-valerolactone (GVL) in GVL as solvent was confirmed by monitoring the dehydration of 13C6-d-fructose to 13C6-5-(hydroxymethyl)-2-furaldehyde (13C6-HMF), the hydration of 13C6-HMF to 13C5-levulinic and 13C-formic acids, followed by their conversion to 13C5-GVL.Keywords: 5-(hydroxymethyl)-2-furaldehyde; acid catalysis; formic acid; fructose; isotope labeling; levulinic acid; Shvo-catalyst; sulfuric acid; γ-valerolactone

Several intermediates and different reaction paths were identified for the acid catalysed conversion of fructose to 5-(hydroxymethyl)-2-furaldehyde (HMF) in different solvents. The structural information combined with results of isotopic-labelling experiments allowed the determination of the irreversibility of the three steps from the fructofuranosyl oxocarbenium ion to HMF as well as the analogous pyranose route.

The reaction of sodium perfluoro-tert-butoxide with benzylic carbon–bromide bond(s) leads to the formation of (nonafluoro-tert-butoxy)methyl ponytail(s), which can enhance the fluorous solubility and partition of aromatics and heterocycles.

Heterogenization methods of homogeneous catalytic systems to render the catalyst and the product(s) in separable phases to allow facile separation are summarized. The applications of two liquid phases with no, limited, or temperature regulated miscibility of the two phases or a solid phase and a liquid phase with no, limited, or temperature regulated solubility of the constituent(s) of the solid phase in the liquid phase are demonstrated on selected examples.

High-pressure in situ IR and NMR investigations of the hydromethoxycarbonylation of 1,3-butadiene (1) to methyl 3-pentenoate (2) in methanol in the presence of Co2(CO)8 and pyridine under carbon monoxide has revealed that the reaction starts by the methanol- and/or pyridine-assisted disproportionation of Co2(CO)8, followed by the establishment of equilibria involving the ionic species [Co(Py)6]2+{[Co(CO)4]−}2, [Co(Py)6]2+[MeO]−[Co(CO)4]−, [PyH]+[Co(CO)4]−, and [MeOH2]+[Co(CO)4]−. The addition of HCo(CO)4 (3) to pyridine or methanol results in the formation of [PyH]+[Co(CO)4]− and [MeOH2]+[Co(CO)4]−, respectively, and 3 is not detectable by either IR or NMR. The ionic 1,4-addition of [MeOH2]+[Co(CO)4]− to 1 is the only pathway to 2-butenylcobalt tetracarbonyl, CH3CH═CHCH2Co(CO)4 (4), via the protonation of 1 followed by the reaction of the C4 carbocation with the counteranion tetracarbonylcobaltate. In the absence of carbon monoxide, 4 could lose a coordinated carbon monoxide to form (η3-C4H7)Co(CO)3 (7) in a reversible reaction. In the presence of carbon monoxide, 4 is converted to the acylcobalt tetracarbonyl species 5 via CO insertion into the Co–carbon bond of 4 followed by the reaction with CO. The pyridine-assisted methanolysis of 5 leads to the formation of the product methyl 3-pentenoate (2) and pyridinium tetracarbonylcobaltate. The key intermediates of the catalytic cycle were isolated and characterized.

Fluorous phosphines having one or more fluorous ponytails containing longer and shorter perfluoroalkyl substituents are reviewed, including their synthesis, some of their basic properties and their applications in biphasic, organometallic and organocatalysis.

Several intermediates and different reaction paths were identified for the acid catalysed conversion of fructose to 5-(hydroxymethyl)-2-furaldehyde (HMF) in different solvents. The structural information combined with results of isotopic-labelling experiments allowed the determination of the irreversibility of the three steps from the fructofuranosyl oxocarbenium ion to HMF as well as the analogous pyranose route.

The reaction of sodium perfluoro-tert-butoxide with benzylic carbon–bromide bond(s) leads to the formation of (nonafluoro-tert-butoxy)methyl ponytail(s), which can enhance the fluorous solubility and partition of aromatics and heterocycles.

Heterogenization methods of homogeneous catalytic systems to render the catalyst and the product(s) in separable phases to allow facile separation are summarized. The applications of two liquid phases with no, limited, or temperature regulated miscibility of the two phases or a solid phase and a liquid phase with no, limited, or temperature regulated solubility of the constituent(s) of the solid phase in the liquid phase are demonstrated on selected examples.

Nonafluoro-t-butyl propyl (1), allyl (2), and propargyl (3) ethers as well as 1,2-bis(nonafluoro-t-butoxy)ethane (4), 1,3-bis(nonafluoro-t-butoxy)-propane (5), and 1,4-bis(nonafluoro-t-butoxy)-butane (6) were prepared by the reaction of sodium nonafluoro-t-butoxide (7) with the corresponding alkyl halides in good yields. Their fluorous partition coefficients and toxicity were also investigated. Computational studies have shown that 4, 5 and 6 exist in a monomeric form in MeOH–CF3C6F11 and they likely aggregate to form oligomers in PhCH3–CF3C6F11.