Acrolein synthesis

Early catalysts for acrolein synthesis were based on cuprous oxide and other heavy metal oxides deposited on inert siHca or alumina supports (39). Later, catalysts more selective for the oxidation of propylene to acrolein and acrolein to acryHc acid were prepared from bismuth, cobalt, kon, nickel, tin salts, and molybdic, molybdic phosphoric, and molybdic siHcic acids. Preferred second-stage catalysts generally are complex oxides containing molybdenum and vanadium. Other components, such as tungsten, copper, tellurium, and arsenic oxides, have been incorporated to increase low temperature activity and productivity (39,45,46). 

The classical selective oxidation catalysts for propene to acrolein synthesis are mixed oxide catalysts such as bismuth molybdate. Despite most of these catalysts being crystalline and exhibiting long-range order, XAS has the advantage of being element specific. It can determine oxidation states and can also directly probe very low concentrations of one metal component in a matrix. 

Isaev and Margolis (152) studied the kinetics of acrolein synthesis from propene under dynamic conditions at atmospheric pressure. The rates of acrolein and carbon dioxide formation were found to be proportional to oxygen concentration in the gas phase and independent of propene concentration. 

The rate of acrolein formation (wx) increases with , and that for C0a (w2) falls down. Variations in the selectivity of acrolein synthesis as a function of those in the electron work function (J >) are shown in Fig. 16. Acceptor impurities added to CuO raise the selectivity by 15 to 20%, and the electron work function by 0.2 to 0.3 ev. To obtain a still greater increase in selectivity it would be necessary to investigate... 

Shell catalysts consist of an compact inert support, usually in sphere or ring form, and a thin active shell that encloses it [4]. Since the active shell has a thickness of only 0.1-0.3 mm, the diffusion paths for the reactants are short. There are many heterogeneously catalyzed reactions in which it would be advantageous to eliminate the role of pore difiusion. This is particularly important in selective oxidation reactions, in which further reactions of intermediate products can drastically lower the selectivity. An example is acrolein synthesis two catalysts with the same active mass but different shell thicknesses differed greatly in selectivity at the high conversions desired in industry (Fig. 6-5). Therefore, if acrolein synthesis is to be operated economically, the shell thickness must be optimized. 

Influence of the shell thickness on the selectivity of acrolein synthesis (BASF, Ludwigshafen, Germany) ... 

Watanabe M, lida T, Aizawa Y, Aida TM, Inomata H. Acrolein synthesis fiom glycerol in hot-compressed... 

Donor substituents on the vinyl group further enhance reactivity towards electrophilic dienophiles. Equations 8.6 and 8.7 illustrate the use of such functionalized vinylpyrroles in indole synthesis[2,3]. In both of these examples, the use of acetyleneic dienophiles leads to fully aromatic products. Evidently this must occur as the result of oxidation by atmospheric oxygen. With vinylpyrrole 8.6A, adducts were also isolated from dienophiles such as methyl acrylate, dimethyl maleate, dimethyl fumarate, acrolein, acrylonitrile, maleic anhydride, W-methylmaleimide and naphthoquinone. These tetrahydroindole adducts could be aromatized with DDQ, although the overall yields were modest[3]. 

Reactions of acrolein with alcohols producing high yields of alkoxypropionaldehyde acetals are also known. Examples of these are displayed in Table 7 (70). The alkoxypropionaldehyde acetals may be useful as solvents or as intermediates in the synthesis of other useful compounds. 

Addition of Mercaptans. One of the largest uses of acrolein is the production of 3-methylmercaptopropionaldehyde [3268-49-3] which is an intermediate in the synthesis of Dj.-methionine [59-51-8] an important chicken feed supplement. 

Acrolein as Diene. An industrially useful reaction in which acrolein participates as the diene is that with methyl vinyl ether. The product, methoxydihydropyran, is an intermediate in the synthesis of glutaraldehyde [111 -30-8]. 

Since aHyl chloride could be converted to glycerol by several routes, the synthesis of glycerol from propylene [115-07-1] became possible. Propylene can also be oxidized in high yields to acrolein [107-02-8]. Several routes for conversion of acrolein to glycerol are shown in Figure 1. 

By substituting paraldehyde for glycerol, 2-methylquinoline [27601-00-9] may be synthesized. The Skraup synthesis is regarded as an example of the broader Doebner-von Miller synthesis. In the case of the Skraup synthesis, the glycerol undergoes an acid-catalyzed dehydration to provide a small concentration of acrolein that is the reactive species. If acrolein itself is used as a reactant, it would polymerize. Crotonaldehyde is the reactive intermediate in the Doebner-von Miller synthesis (28). 

Chemical Production. Glyciae, DL-methionine, and dl-alanine ate produced by chemical synthesis. From 1964 to 1974, some glutamic acid was produced chemically (48). The synthetic amino acid with the largest production is DL-methionine from actoleia (see Acrolein and derivatives). The iadustrial production method is shown ia the foUowiag (210). 

The formation of quinoline [91-22-5] (51) from aniline and acrolein involves formation of two bonds during the ring synthesis. 

Acrolein (CH2=CHCHO) can be substituted for formaldehyde and acetaldehyde in the above reaction to give similar results, but the proportion of (3) is higher than when acetaldehyde and formaldehyde are fed separately. Acrolein may be formed as one of the first steps to pyridine (1) and P-picoline (3) formation. There are many variations on the vapor-phase synthesis of pyridine itself. These variations are the subject of many patents in the field. 

Another synthesis of Lyral (51) consists of the reaction of myrcene with acrolein to give the myrac aldehyde [37677-14-8] (52). The aldehyde group, which is sensitive to acid hydration conditions with strong acids, has to be protected by formation of the morpholine enamine. The enamine is then hydrolyzed on workup after the acid-catalyzed hydration to produce Lyral (93—95). 

The performance of many metal-ion catalysts can be enhanced by doping with cesium compounds. This is a result both of the low ionization potential of cesium and its abiUty to stabilize high oxidation states of transition-metal oxo anions (50). Catalyst doping is one of the principal commercial uses of cesium. Cesium is a more powerflil oxidant than potassium, which it can replace. The amount of replacement is often a matter of economic benefit. Cesium-doped catalysts are used for the production of styrene monomer from ethyl benzene at metal oxide contacts or from toluene and methanol as Cs-exchanged zeofltes ethylene oxide ammonoxidation, acrolein (methacrolein) acryflc acid (methacrylic acid) methyl methacrylate monomer methanol phthahc anhydride anthraquinone various olefins chlorinations in low pressure ammonia synthesis and in the conversion of SO2 to SO in sulfuric acid production. 

In recent years the solid-phase hydrosilylation reaction was successfully employed for synthesis of hydrolytically stable surface chemical compounds with Si-C bonds. Of special interest is application of this method for attachment of functional olefins, in particular of acrolein and some chiral ligands. Such matrices can be used for subsequent immobilization of a wide range of amine-containing organic reagents and in chiral chromatography. 

S K R A U P Quitxiline synthesis Quinoline synthesis from anilines and acrolein or glycerol... 

Attenlion should be drawn to ihe use of tin oxide systems as heterogeneous catalysts. The oldest and mosi extensively patented systems are the mixed lin-vanadium oxide catalysis for the oxidation of aromatic compounds such as benzene, toluene, xylenes and naphthalene in the. synthesis of organic acids and acid anhydride.s. More recenily mixed lin-aniimony oxides have been applied lo the selective oxidaiion and ammoxidaiion of propylene to acrolein, acrylic acid and acrylonilrile. 

For the Skraup synthesis, glycerol 2 is used as starting material in the presence of concentrated sulfuric acid (see scheme above) it is dehydrated to acrolein 6. Although it is assumed that the reactive carbonyl component in the Skraup reaction actually is acrolein, attempts to use acrolein directly, instead of glycerol, proved to be unsuccessful." ... 

The main use of acrolein is to produce acrylic acid and its esters. Acrolein is also an intermediate in the synthesis of pharmaceuticals and herhicides. It may also he used to produce glycerol hy reaction with isopropanol (discussed later in this chapter). 2-Hexanedial, which could he a precursor for adipic acid and hexamethylene-diamine, may he prepared from acrolein Tail to tail dimenization of acrolein using ruthenium catalyst produces trans-2-hexanedial. The trimer, trans-6-hydroxy-5-formyl-2,7-octadienal is coproduced. Acrolein, may also he a precursor for 1,3-propanediol. Hydrolysis of acrolein produces 3-hydroxypropionalde-hyde which could he hydrogenated to 1,3-propanediol. ... 

Acifluorfen, synthesis of, 683 Acrolein, structure of, 697 Acrylic acid, pKa of, 756 structure of. 753 Activating group (aromatic substitution), 561 acidity and, 760 explanation of, 564-565 Activation energy, 158 magnitude of, 159 reaction rate and, 158-159 Active site (enzyme), 162-163 citrate synthase and, 1046 hexokinase and, 163... 

For the previous preparation of a mixed acrolein acetal and its use in an RCM reaction during callystatin A total synthesis, see Crimmins MT, King BW (1998) J Am Chem Soc 120 9084... 

Co-adsorption experiments show a complex role of the nature and concentration of chemisorbed ammonia species. Ammonia is not only one of the reactants for the synthesis of acrylonitrile, but also reaction with Br()>nsted sites inhibits their reactivity. In particular, IR experiments show that two pathways of reaction are possible from chemisorbed propylene (i) to acetone via isopropoxylate intermediate or (ii) to acrolein via allyl alcoholate intermediate. The first reaction occurs preferentially at lower temperatures and in the presence of hydroxyl groups. When their reactivity is blocked by the faster reaction with ammonia, the second pathway of reaction becomes preferential. The first pathway of reaction is responsible for a degradative pathway, because acetone further transform to an acetate species with carbon chain breakage. Ammonia as NH4 reacts faster with acrylate species (formed by transformation of the acrolein intermediate) to give an acrylamide intermediate. At higher temperatures the amide may be transformed to acrylonitrile, but when Brreform ammonia and free, weakly bonded, acrylic acid. The latter easily decarboxylate forming carbon oxides. 

Ru4 bears a Me and Ru5 a Et moiety instead of one of the mesityl-residues leads, in the synthesis of 98, to a higher Z-selectivity than HII. In contrast, the use of Ru5 for CM with acroleine 100, which usually reacts with relatively high Z-selectivities, results in higher -selectivity than HIT (Scheme 3.15). 

In the same area, a (5)-tryptophan-derived oxazaborolidine including a p-tolylsulfonylamide function has been used by Corey et al. to catalyse the enantioselective Diels-Alder reaction between 2-bromoacrolein and cyclo-pentadiene to form the corresponding chiral product with an unprecedented high (> 99% ee) enantioselectivity (Scheme 5.27)." This highly efficient methodology was extended to various 2-substituted acroleins and dienes such as isoprene and furan. In addition, it was applied to develop a highly efficient total synthesis of the potent antiulcer substance, cassiol, as depicted in Scheme 5.21... 

The Heck coupling reaction appeared to be a route of choice to achieve the synthesis of the modified-DIOP ligands. We previously studied the palladium-catalyzed coupling of acrolein and acrolein acetals with several polyaromatic and heteroaromatic bromides either in the presence of homogeneous or heterogeneous catalytic systems (6, 7). After optimization of the reaction conditions, high conversions and selectivities were achieved except with anthracenyl derivatives (8). Based on these results, we developed the synthesis of the desired ligands. The... 

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