Catalyst and yield

Remove contaminants from the Fischer-Tropsch-derived oil to protect downstream catalysts and yield suitable products. 

Adib A process for extracting isobutene from petroleum fractions by reaction with phenol. The reaction takes place in the gas phase, over an acid catalyst, and yields all the mono-, di-, and tri-butyl phenols. Heating this mixture liberates isobutene the phenol and the catalyst are recovered for re-use. Piloted in Argentina in the 1980s. 

Bromobenzenes are converted into the corresponding chloro compounds on reaction with aqueous sodium hypochlorite in the presence of tetra-n-buty lammoni um hydrogen sulphate [40]. The reaction is pH dependent. At pH > 10, the bromobenzenes are effectively inert, but over the pH range 7.5-9, conversion occurs into the chlorobenzenes without any side reactions and the reaction appears to be light-induced. At more acidic levels (pH 4-5), bromobenzene is converted quantitatively into chlorobenzene within one hour. No reaction occurs in the absence of the catalyst and yields from light and dark reactions are comparable. Side reactions are observed, however, with substituted bromobenzenes under these low pH conditions. 

Rhodium is a unique metal since it can catalyze several transformations.222,223 It is an active methanation catalyst and yields saturated hydrocarbons on an inert support. Methanol is the main product in the presence of rhodium on Mg(OH)2. Transition-metal oxides as supports or promoters shift the selectivity toward the formation of C2 and higher oxygenates. 

The acetylation of carbazole by acetic anhydride in the presence of boron trifluoride produces the 9-acetyl derivative. Further acetylation requires more vigorous conditions, using aluminum trichloride as a catalyst, and yields 2,9-diacetylcarbazole, which, upon base-catalyzed hydrolysis, produces 2-acetylcarbazole (80T3017). Acetylation of 1-phenyl-isoindole under mild conditions in the presence of pyridine yields l-acetyl-3-phenylisoin-dole, whereas the presence of an ester group at the 1-position deactivates the ring sufficiently to prevent acylation (81AHC(29)34l). 

Reductive amination of ketones using p-anisidine and the Hantzsch ester for transfer hydrogenation is a low-yielding reaction in toluene at room temperature, but thiourea is an efficient catalyst, and yields of up to 94% are reported at 50 °C.334 A mechanism involving thiourea hydrogen bonding to the intermediate imine is supported by ab initio calculations. 

Since the Schrock carbyne is active in the transalkylidynation reaction, the possibility of ring-opening polymerisation of cycloalkynes by acetylene transalkylidynation catalysts (metal alkylidyne complexes) has been evaluated [151]. Unfortunately, cyclooctyne is one of the few relatively stable strained cyclic acetylenes, but it is not strained enough to react selectively with the catalyst and yield a polymer according to the scheme... 

The initial oligomer as an aqueous solution is obtained from the reaction of urea and formaldehyde at 100°C and pH = 5.8-6 [130]. The process of polycondensation occurs in the presence of acidic catalyst and yields a tri-dimensional polymer, releasing water and formaldehyde [131]. Surfactants are added as foaming agent to the initial composition for the formation of urea polymer foams [125,130]. Various additives are employed to improve the sanitary properties of these plastics. For example, ammonium carbonate reduces the content of free formaldehyde, while addition of carbonates of alkaline metals inhibits corrosion [125]. 

Biginelli reaction (Figure 2.1)P The 1,3-dicarbonyl compound, aldehyde and urea are heated to around 100 °C for 1 h without any need for solvent or catalyst and yield the dihydropyrimidone in good to excellent yields. Performing the same reaction in refluxing VOCs did not yield any product, indicating a special advantage for a solventless procedure in this case. The reaction has been scaled up successfully to the 1 kg level and the only additional solvents required to work up the product effectively are water and ethanol. 

Diels-Alder Reactions. It has been demonstrated that the ligand-metal complexes derived from (5,5)-/-Bu-box and a mild Lewis acid such as Cu(OTf)2 are very efficient chiral catalysts for the Diels-Alder reaction with cyclopentadiene and substituted acylimide derivatives. Among various ligands examined, the (5,5)-/-Bu-box ligand consistently provided a very high level of endo/exo selectivity as well as endo enantioselectivity (90-98% ee with 5-10 mol % catalyst) and yield (82-92%) with a number of substituted dienophiles. 

Telomerizations have been among the first reactions tested under biphasic conditions [45, 190], starting with butadiene and methanol on Pd/TPPMS catalysts and yielding l-methoxy-2,7-octadiene. The telomerization in the presence of water as reactant (hydrodimerization cf Scheme 1) has been commercialized [15, 31, 42-44]. These biphasic developments of the Kuraray Corporation yield 1-octanol or 1,9-nonanediol, respectively (cf [15, 31, 42 4, 86, 133, 137, 244 e] and Section 2.3.5). Similar developments (but without technical realization) have been described by BASF [134], Mitsubishi [135], and Shell [136], and others [215 d, 242, 268]. The telomerization of butadiene and ammonia may also be biphasic [243]. 

The following discussion of catalysts and yields includes new observations by Wilgus and Gates of the Eastman Kodak Co. Thus these investigators report that toluquinone (1) on reaction with acetic anhydride and sulfuric acid gives in 90% yield a mixture shown by VPC analysis to represent a yield of 78% of the 2,4,5-triacetoxy derivative (2) and a 14.5% yield of 2,3,5-isomer (3). Thus the reaction... 

Reid98 recently employed high pressures while attempting the oxidation of heavy hydrocarbons but does not give detailed data. Extensive investigations on the oxidation of paraffin wax under high pressures have been made by Fischer.90 This work showed iron and copper salts to be the best catalysts and yields as high as 74 per cent of fatty acids were obtained. 

Table I gives a comprehensive summary of the conversion of D-glucosides (8) into the corresponding D-glucosiduronic acids (9), and indicates the reaction conditions, catalyst, and yield. Glucosides of most aliphatic alcohols are generally oxidized under standard conditions at 60 to 80°...

The liquid scrubbed hydrogen sulfide is mixed with the olefinic inaterial (usually a 165-200°C fraction of propylene-isobutylene polymer) in a molar ratio of 1.5 1 and passed into a catalyst chamber in the liquid phase. The residence time in the catalyst case is 1 hr with the temperature under 150 C. The conversion is about 35 per cent or better with a very active catalyst, and yields vary from 60-80 per cent based on olefin charged. The product is purified by vacuum fractionation after the recycle hydrogen sulfide is stripped at about 50 lb pressure. The (d fin is taken overhead in one column and the mercaptan in a second. The final material contains 90 plus per cent isomeric mercaptans. 

Step 4 The product of step 3 transfers a proton to water to regenerate the acid catalyst and yield the neutral form of the product. 

The peptide-catalysed stereospecific synthesis of tetroses (threose and erythrose) was reported by Weber and Pizzarello using homochiral L-configured dipeptides. " In the course of their investigations several dipeptides containing a- or (3-branched amino acids were employed revealing peptide 46 as the most useful catalyst and yielding the u-erythrose in enantiomeric excess of 82%, whereas the u-threose was obtained nearly racemic (Scheme 13.26). Generally, most of the tested peptides followed this trend and had an asymmetric effect on erythrose, whereas threose remained unaffected. 

The observed excellent stereoselectivities (dr=91 9 to >95 5, 94 to >99% ee) could be ascribed to the steric hindrance created by the employed catalyst in each step of the catalytic cycle reported below (Scheme 2.56). Once the chiral amine (S)-70 activates the acrolein 131 as electrophile by generating the vinylogous iminium ion A, the indole 171 performs an intermolecular Friedel-Crafts-type reaction. The resulting enamine B acts as nucleophile in the Michael addition of the nitroalkene 140 leading to the iminium ion D, which upon hydrolysis liberates the catalyst and yields the intermediate aldehyde 173. The latter compound enters in the second cycle by reacting with the iminium ion A, previously formed by the free catalyst. The subsequent intramolecular enamine-mediated aldol reaction of E completes the ring closure generating the intermediate F, which after dehydration and hydrolysis is transformed in the desired indole 172. 

CASREACT, as an online database, it is possible to search for reactions and reaction types, for catalysts and yields, for substructures and compound classes. Every two weeks - according to Chemical Abstracts - 3000 to 4000 new reactions are reported from the recent literature, complete with CA abstract, title of the publication and name of the author. 

---