Formation Of Allylic Alcohols Research Articles

Influence of WO3 Content in Phosphated Tungsten-Zirconium Oxide Catalysts on the Catalytic Pathways of Glycerol Transformation.

The catalytic performance of phosphate-stabilized WOx-ZrO2 compositions in gas-phase glycerol dehydration has been investigated. Results show that varying WO3 concentrations direct the process towards either acrolein or allyl alcohol formation. Catalysts with low WOx content exhibit strong Lewis acid sites (Zr4+ and W6+), where these metal ions likely function as redox sites, facilitating glycerol hydrogenolysis to produce allyl alcohol. Higher WO3 concentrations (exceeding 20 wt.%) lead to the shielding of some W6+ and Zr4+ sites by polytungstate surface complexes, which are strong Brønsted acid sites. This alteration promotes glycerol dehydration through the removal of two water molecules, thereby shifting the selectivity towards acrolein formation.

Direct C–C Bond Formation of Allylic Alcohols with CO2 toward Carboxylic Acids by Photoredox/Nickel Dual Catalysis

Direct C–C Bond Formation of Allylic Alcohols with CO₂ toward Carboxylic Acids by Photoredox/Nickel Dual Catalysis

Conversion of glycerol over vanadium supported beta zeolite: Role of acidity and alkali cations

Different vanadium supported beta zeolites modified with Cs and K, were used as catalysts for the conversion of glycerol, in gas phase, without any external reductant. The catalytic data show that all the catalysts studied are active in the conversion of glycerol and that the presence of vanadium oxide species promotes the formation of allyl alcohol. Moreover, modification of the vanadium-based catalysts with Cs or K changes the vanadium species and puts in evidence the importance of the acidity in this process. A low density of acid sites favors the formation of allyl alcohol, in detriment of acrolein one. The data also indicate that the formation of these compounds is closely related and could be explained using the same mechanistic path. • Vanadium oxide species promote the direct formation of allyl alcohol from glycerol. • The catalytic behavior depends on the acidity and presence of alkaline metals. • Formation of allyl alcohol and acrolein is intimately related

Direct synthesis of allyl alcohol from glycerol over CoFe alloy

Allyl alcohol is a pivotal intermediate and it is of great importance to find a new way for the selective production of allyl alcohol from renewable and surplus glycerol. In this work, we want to report the high performance of CoFe alloy for the direct synthesis of allyl alcohol from glycerol. This alloy catalyst was prepared via the controlled calcination and reduction of CoFe-ZIF precursor. Characterization results indicate that Co can improve the activation of hydrogen and Fe enhances the acidity of prepared CoFe alloy. The activated hydrogen and acid sites in CoFe alloy played a synergistic effect for the selective formation of allyl alcohol directly from glycerol. The selectivity of allyl alcohol remained higher than 68.7 % with a 89.7 % conversion of glycerol at 250 °C, 2 MPa and WHSV = 2.6 h−1. And the reaction mechanism over CoFe alloy was proposed on the basis of controlled experiments.

ChemInform Abstract: Lewis Acid Catalyzed Friedel—Crafts Alkylation of Alkenes with Trifluoropyruvates.

AbstractThe title reaction of styrenes with trifluoropyruvates results in the formation of allylic alcohols in high yields using a Ni(ClO4)2/bipyridine catalyst system.

Selective oxidation of carotenoid-derived aroma compounds by CYP260B1 and CYP267B1 from Sorangium cellulosum So ce56.

Due to their bioactive properties as well as their application as precursors in chemical synthesis, hydroxylated isoprenoids and norisoprenoids are very valuable compounds. The efficient hydroxylation of such compounds remains a challenge in organic chemistry caused by the formation of a variety of side products and lack of overall regio- and stereoselectivity. In contrast, cytochromes P450 are known for their selective oxidation under mild conditions. Here, we demonstrate for the first time the ability of myxobacterial CYP260B1 and CYP267B1 from Sorangium cellulosum So ce56 to oxidize such carotenoid-derived aroma compounds. A focused library of 14 substrates such as ionones, damascones, as well as some of their isomers and derivatives was screened in vitro. Both P450s were capable of an efficient oxidation of all tested compounds. CYP260B1-dependent conversions mainly formed multiple products, whereas conversions by CYP267B1 resulted predominantly in a single product. To identify the main products by NMR spectroscopy, an Escherichia coli-based whole-cell system was used. CYP267B1 showed a hydroxylase activity towards the formation of allylic alcohols. Likewise, CYP260B1 performed the allylic hydroxylation of β-damascone [(E)-1-(2,6,6-trimethylcyclohex-1-enyl)but-2-en-1-one] and δ-damascone [(E)-1-(2,6,6-trimethylcyclohex-3-enyl)but-2-en-1-one]. Moreover, CYP260B1 showed an epoxidase activity towards β-ionone [(E)-4-(2,6,6-trimethylcyclohex-1-enyl)but-3-en-2-one] as well as the methyl-substituted α-ionone derivatives raldeine [(E)-1-(2,6,6-trimethylcyclohex-2-enyl)pent-1-en-3-one] and isoraldeine [(E)-3-methyl-4-(2,6,6-trimethylcyclohex-2-enyl)but-3-en-2-one]. In addition, to known products, also novel products such as 2-OH-δ-damascone [(E)-1-(5-hydroxy-2,6,6-trimethylcyclohex-3-enyl)but-2-en-1-one], 3-OH-allyl-α-ionone [(E)-1-(4-hydroxy-2,6,6-trimethylcyclohex-2-enyl)hepta-1,6-dien-3-one], and 4-OH-allyl-β-ionone [(E)-1-(3-hydroxy-2,6,6-trimethylcyclohex-1-enyl)hepta-1,6-dien-3-one] were identified during our studies.

First Principles Calculations for Hydrogenation of Acrolein on Pd and Pt: Chemoselectivity Depends on Steric Effects on the Surface.

The chemoselective hydrogenation of acrolein on Pt(111) and Pd(111) surfaces is investigated employing density functional theory calculations. The computed potential energy surfaces together with the analysis of reaction mechanisms demonstrate that steric effects are an important factor that governs chemoselectivity. The reactions at the C=O functionality require more space than the reactions at the C=C functionality. Therefore the formation of allyl alcohol is more favorable at low coverage, while the reduction of the C=C bond and the formation of propanal becomes kinetically more favorable at higher coverage. The elementary reaction steps are found to follow different reaction mechanisms, which are identified according to terminology typically used in organometallic catalysis. The transition state scaling (TSS) relationship is demonstrated and the origin of multiple TSS lines is linked to variation of an internal electronic structure of a carbon skeleton.

First Principles Calculations for Hydrogenation of Acrolein on Pd and Pt: Chemoselectivity Depends on Steric Effects on the Surface

AbstractThe chemoselective hydrogenation of acrolein on Pt(111) and Pd(111) surfaces is investigated employing density functional theory calculations. The computed potential energy surfaces together with the analysis of reaction mechanisms demonstrate that steric effects are an important factor that governs chemoselectivity. The reactions at the C=O functionality require more space than the reactions at the C=C functionality. Therefore the formation of allyl alcohol is more favorable at low coverage, while the reduction of the C=C bond and the formation of propanal becomes kinetically more favorable at higher coverage. The elementary reaction steps are found to follow different reaction mechanisms, which are identified according to terminology typically used in organometallic catalysis. The transition state scaling (TSS) relationship is demonstrated and the origin of multiple TSS lines is linked to variation of an internal electronic structure of a carbon skeleton.

Conversion of Glycerol into Useful Chemicals over Iron Oxide-based Catalyst

Catalytic conversion of glycerol with iron oxide-based catalysts was investigated for the production of useful chemicals. The catalytic reaction was carried out in a fixed-bed flow reactor at 623 K under atmospheric pressure. Useful chemicals such as allyl-alcohol, propylene and ketones were produced from glycerol through two main pathways: formation of allyl alcohol and propylene (Pathway I), and formation of hydroxyacetone and acrolein (Pathway II). Hydroxyacetone in Pathway II is easily converted into carboxylic acids followed by ketonization to form acetone, methyl ethyl ketone and pentanone. An increase in the W/F (weight ratio of catalyst to feedstock) value allowed the consecutive reactions to progress and the final products were 24 mol%-carbon of propylene and 25 mol%-carbon of ketones. Moreover, addition of alkaline metals to the catalyst increased the yield of allyl alcohol. This study demonstrates the production of useful chemicals from glycerol (crude glycerol and reagent glycerol). The effects of catalyst composition and experimental conditions on these yields are discussed, based on investigations of the reaction pathways and mechanisms.

The effect of catalyst modification on the conversion of glycerol to allyl alcohol

Conversion of glycerol to allyl alcohol was carried out over an iron on alumina catalyst. With the aim of enhancing selectivity towards the desired product and to reduce acrolein formation (a detrimental impurity in the subsequent epoxidation of allyl alcohol) the supported iron catalyst was modified using alkali metals. It was found that lithium, sodium, potassium, rubidium and caesium deposition on the catalyst surface increased allyl alcohol yield and reduced the rate of catalyst deactivation. Coincidently, acrolein selectivity decreased by up to 75% following treatment with the alkali salt.Changes in the product distribution were determined to be associated with altering the acid/base properties of the catalyst, as confirmed by isopropanol dehydration/dehydrogenation, ammonia and carbon dioxide temperature programmed desorption. The treatment was also found to influence the physical properties of the catalyst surface. A correlation between acid to basic site concentration and allyl alcohol selectivity was established. A reduction in the former value results in an enhancement in the rate of allyl alcohol formation. A reaction mechanism was developed based on the effect of iron and alkali metals catalysing the conversion of glycerol into allyl alcohol. The proposed catalyst modification technique is a straightforward method, readily applicable at a larger scale due to the simplicity of the alkali inclusion and its striking influence on the reaction selectivity.

Acrolein Hydrogenation on Ni(111)

Acrolein hydrogenation via allyl alcohol, propanal, and enol into propanol on the Ni(111) surface has been investigated using the spin-polarized periodic density functional theory method. On the basis of the computed adsorption energies and effective hydrogenation barriers, acrolein hydrogenation into propanal and allyl alcohol obeys the Langmuir–Hinshelwood mechanism and propanal formation is more favored kinetically and thermodynamically than allyl alcohol formation. Hydrogenation of propanal and allyl alcohol should follow the Eley–Rideal mechanism. The adsorption energies of acrolein, allyl alcohol, and propanal along with the partial hydrogenation selectivity on Ni, Au, Ag, and Pt catalysts have been compared and discussed.

A category approach to predicting the repeated-dose hepatotoxicity of allyl esters

We tested a category approach to predict the hepatotoxic effects of repeated doses of allyl esters using a new database for repeated-dose toxicity. Based on information on hepatotoxic mechanism of allyl acetate, the category was defined as allyl esters that are hydrolyzed to allyl alcohol. Allyl alcohol is readily oxidized to acrolein in the liver, causing hepatotoxicity. Seventeen marketed allyl esters were obtained and grouped into category by identifying or predicting allyl alcohol formation. Allyl esters with a saturated straight alkyl carboxylic acid moiety (allyl acetate, hexanoate and heptanoate as tested species, and allyl butyrate, pentanoate, octanoate, nonanoate and decanoate as untested species) are likely similar in rate of ester hydrolysis, thereby defining subcategory 1. NOAEL and LOAEL for the hepatotoxic effects were estimated at 0.12 and 0.25mmol/kg/d for the untested species, based on those of allyl acetate. The remaining nine allyl esters with other alkyl or aromatic carboxylic acid moieties were placed in subcategory 2: their hepatotoxicity levels were not predictable due to an unclear match between their degree of structural complexity and rate of hydrolysis. Our results demonstrate the usefulness of the category approach for predicting the hepatotoxicity of untested allyl esters with saturated straight alkyl chains.

Catalytic effect of molybdenum oxo-species on reduction of allyl alcohol at a Pt electrode in strongly acidic solutions

Kinetics of the electroreduction of molybdenum(VI) species and allyl alcohol (AA) alone as well as of AA after the addition of Na2MoO4 to perchloric acid solutions (HClO4) on a polycrystalline Pt electrode was characterized under the conditions of cyclic voltammetry (CV). Using the XPS technique evidence was provided that mixed valent Mo(V/VI) layer is formed upon reduction of Mo(VI) moieties present in 1M HClO4 solution, while the cationic Mo(VI) species existing in strongly acidified solutions are reduced successively to relevant Mo(V) and Mo(III) species at E<0.25V. It was ascertained that a relatively fast adsorption of AA precedes its hydrogenation to propene and propane in the absence of Mo(VI) in the electrolyte solution. However, the Pt surface is partially poisoned with CO-like species due to a rupture of the C3-carbon backbone in the potential range of hydrogen adsorption–desorption. A considerable enhancement of the cathodic current corresponding to the AA electroreduction was discovered in the presence of cationic Mo(VI) species in 4M HClO4 solutions. Simultaneously, the rate of electroreduction of this species was effectively increased on the addition of AA in comparison with that in the absence of AA. According to the proposed reaction pathways, AA is reduced via a catalytic chemical reaction with Mo(III) and/or Mo(V) cationic species. The cyclic regeneration of the electroactive Mo(VI) and/or Mo(V) species accounts for the observed catalytic phenomenon. Furthermore, the decomposition of the C3-carbon skeleton of AA molecules and formation of strongly adsorbed CO-like species is eliminated in the presence of Mo(VI). The optimal conditions for monitoring of AA and/or Mo(VI) in electrochemical devices with a Pt electrode are specified.

Catalytic activity of bifunctional transition metal oxide containing phosphated alumina catalysts in the dehydration of glycerol

A systematic study was conducted to evaluate the effect of different transition metal oxide loaded on phosphated alumina as catalysts for the gas-phase dehydration of glycerol. The series of MeO–Al 2O 3-PO 4 catalysts at the constant Me:Al ratio was prepared by impregnation of alumina and characterized with respect to their textural properties, crystallinity, acidity and reducibility. Catalytic performance was tested at the constant operating conditions in the presence of steam. It was found that conversion, and acrolein formation increased with the increase of the total catalyst acidity; i.e., the selectivity to acrolein increased in the order: Ce < Mn < Cr < V ∼ Fe < Cu < Mo < W. The highest selectivity towards acrolein (54%) was observed over W contained catalyst after a long-term test, i.e., 30 h. For Ce, Fe and Cr catalysts low selectivity to acrolein (12–23%) was observed. Contrary CuO x –Al 2O 3-PO 4 catalyst favored the formation of acetol (50%). In the case of Cr-, Mn- and V-containing alumina phosphates an enhanced formation of acetaldehyde and CO x , was observed as a result of destructive glycerol cleavage. The V- and Fe-containing catalysts promote the formation of allyl alcohol. Finally, the change of the total acidity, oxidation state and crystallinity for spent catalysts was studied by NH 3-TPD, TPO, TPR and XPS analysis. In general, MO–Al 2O 3-PO 4 catalysts showed improved stability against deactivation which can be attributed to the oxidative properties of the transition metal oxide components that enhance coke removal.

Gas-phase conversion of glycerol over mixed metal oxide catalysts

A series of aluminophosphates (APO) catalysts with Ce, Cu, Cr, Fe, Mn, Mo, V, and W oxide loading at a constant ratio M: Al = 1: 10 and PO4: Al = 1: 12 were prepared and characterized by N2 physisorption, XRD and NH3-TPD. Gas-phase dehydration of glycerol to produce acrolein and acetol was investigated at 280°C in presence of water. Conversion and product distribution depended on the intrinsic acidity and the type of transition metal oxide. Best selectivity to acrolein (52–58%) was obtained for W- und Mo-APO catalysts. Cr-, Mn- and W- oxide containing catalysts enhanced the formation of phenol, acetaldehyde and COx. The catalysts containing V- and Fe-oxide promoted the formation of allyl alcohol. All catalysts showed long term stability, which can be attributed to the redox ability of the metal oxides that enhances the removal of coke deposits. The investigated catalyst a specially W-APO and Mo-APO can be recommended for further controlled trials on a pilot plant for selective conversion of water solution of glycerol to acrolein and/or acetol.

Chemoselective Catalytic Hydrogenation of Acrolein on Ag(111): Effect of Molecular Orientation on Reaction Selectivity

The adsorption and hydrogenation of acrolein on the Ag(111) surface has been investigated by high resolution synchrotron XPS, NEXAFS, and temperature programmed reaction. The molecule adsorbs intact at all coverages and its adsorption geometry is critically important in determining chemoselectivity toward the formation of allyl alcohol, the desired but thermodynamically disfavored product. In the absence of hydrogen adatoms (H(a)), acrolein lies almost parallel to the metal surface; high coverages force the C=C bond to tilt markedly, likely rendering it less vulnerable toward reaction with hydrogen adatoms. Reaction with coadsorbed H(a) yields allyl alcohol, propionaldehyde, and propanol, consistent with the behavior of practical dispersed Ag catalysts operated at atmospheric pressure: formation of all three hydrogenation products is surface reaction rate limited. Overall chemoselectivity is strongly influenced by secondary reactions of allyl alcohol. At low H(a) coverages, the C=C bond in the newly formed allyl alcohol molecule is strongly tilted with respect to the surface, rendering it immune to attack by H(a) and leading to desorption of the unsaturated alcohol. In contrast with this, at high H(a) coverages, the C=C bond in allyl alcohol lies almost parallel to the surface, undergoes hydrogenation by H(a), and the saturated alcohol (propanol) desorbs.

Reactions of chloromethyloxirane and dihalopropanols with chalcogens in basic reducing systems

Chloromethyloxirane and 2,3-dibromopropan-1-ol reacted with a solution of selenium or tellurium in the system hydrazin hydrate-potassium hydroxide (K2Se2, K2Te2) to give allyl alcohol; the reaction was accompanied by regeneration of the initial free chalcogen. 1,3-Dichloropropan-2-ol reacted with selenium in the same system to give oligomeric product having a 2-hydroxypropane-1,3-diyldiseleno monomeric unit, while the reaction with tellurium led to the formation of allyl alcohol and almost complete regeneration of initial tellurium. Probable reaction mechanisms are discussed. Polyselenide oligomers containing a hydroxy group in a monomeric unit were formed in reactions of chloromethyloxirane and 1,3-dichloropropan-2-ol with selenium in the system hydrazine hydrate-2-aminoethanol. Under analogous conditions 2,3-dibromopropan-1-ol was converted into allyl alcohol with regeneration of elemental selenium. Reductive cleavage of polyselenide oligomers gave Se-methyl derivatives of 2-hydroxypropane-1,3-diselenol.

Enantiomerically Enriched Allylic Alcohols and Allylic Amines via C–C Bond-Forming Hydrogenation: Asymmetric Carbonyl and Imine Vinylation

Hydrogenation of alkynes in the presence of carbonyl compounds and imines using cationic rhodium(I) and iridium(I) precatalysts enables the formation of allylic alcohols and allylic amines, respectively. Through the use of hydrogenation catalysts modified by chiral ligands, allylic alcohols and allylic amines may be generated in highly optically enriched forms. Hydrogenative fragment couplings of this type circumvent the use of preformed organometallic reagents and avoid the generation of stoichiometric byproducts.

Isoquinolone derivatives via a furan recyclization reaction

A new approach to the synthesis of isoquinolone derivatives has been developed. It is based on the protolytic recyclization of amides of 2-carboxybenzylfurans. It was shown that the reaction proceeds via formation of allylic alcohols of isoquinolone series, which under acidic conditions undergo isomerization into the corresponding ketones. A new condensed heterocyclic system of furo[2′,3′:3,4]cyclohepta[1,2- c]isoquinolin-8(6 H)-one has been synthesized.

BTS Abstracts Spring 2007, Oral Communications Abstracts

We tested a category approach to predict the hepatotoxic effects of repeated doses of allyl esters using a new database for repeated-dose toxicity. Based on information on hepatotoxic mechanism of allyl acetate, the category was defined as allyl esters that are hydrolyzed to allyl alcohol. Allyl alcohol is readily oxidized to acrolein in the liver, causing hepatotoxicity. Seventeen marketed allyl esters were obtained and grouped into category by identifying or predicting allyl alcohol formation. Allyl esters with a saturated straight alkyl carboxylic acid moiety (allyl acetate, hexanoate and heptanoate as tested species, and allyl butyrate, pentanoate, octanoate, nonanoate and decanoate as untested species) are likely similar in rate of ester hydrolysis, thereby defining subcategory 1. NOAEL and LOAEL for the hepatotoxic effects were estimated at 0.12 and 0.25 mmol/kg/d for the untested species, based on those of allyl acetate. The remaining nine allyl esters with other alkyl or aromatic carboxylic acid moieties were placed in subcategory 2: their hepatotoxicity levels were not predictable due to an unclear match between their degree of structural complexity and rate of hydrolysis. Our results demonstrate the usefulness of the category approach for predicting the hepatotoxicity of untested allyl esters with saturated straight alkyl chains.