Aldehydes hydrogen added

S g of ethyl glycinate hydrochloride were dissolved in 400 cc of ethanol and 33.5 g of salicylic aldehyde were added. It is refluxed for half an hour and cooled. 38 cc of triethylamlne and 25 g of Raney nickel are then added whereafter hydrogenation is carried out at room temperature and under atmospheric pressure. After hydrogen adsorption was complete, the mixture was filtered and the alcohol evaporated off. The residue was taken up with acidified water, extracted with ether to eliminate part of the by-products, consisting mainly of o-cresol, then made alkaline with ammonia and extracted with ethyl acetate. The solvent was removed in vacuo and the residue crystallized from ether/petroleum ether. 36.7 g of o-hydroxybenzyl-aminoacetlc acid ethyl ester melting at 47°C are obtained. 

A solution of 1 equivalent of the oxazolidinone in diethyl ether is cooled to —78 C. To the resultant suspension are added 1.4 equivalents of triethylamine. followed by 1.1 equivalents of dibutylboryl triflate. The cooling bath is removed and the reaction mixture is stirred at 25 °C for 1.5 h. The resultant two-phase mixture is cooled to — 78 "C with vigorous stirring. After 1 equivalent of aldehyde is added, the reaction is stirred at —78 °C Tor 0.5 h, and 0 "C for 1 to 2 h. The solution is diluted with diethyl ether, washed with 1 N aq sodium bisulfate, and concentrated. Following oxidation with 30% aq hydrogen peroxide (10 equivalents, 1 1 methanol/water, 0 C. 1 h), extractive workup and chromatographic purification, the aldol adduct is obtained with >99% diastcrcomeric purity. 

Aldol reactions between two different carbonyl compounds are called mixed or crossed aldol reactions. With aqueous bases, these reactions are of little synthetic value if both reactants have a-hydrogens because they afford mixtures of products. However, under carefully controlled conditions, it is possible to condense ketones with aldehydes in the presence of dilute sodium hydroxide to furnish P-hydroxyke-tones, provided that the aldehyde is added slowly to the ketone. 

Attempts to prepare tertiary amines by reductive alkylation have in general proved unsatisfactory the only significant reactions are the methylation of secondary and the dimethylation of primary amines by formaldehyde. Bowman and Stroud1008 described the preparation of a series of aliphatic dimethyl-amino acids by hydrogenation of mixtures of amino acids and formaldehyde in the presence of palladium-charcoal at atmospheric pressure. In most cases results are improved if the aldehyde is added gradually to the reaction mixture. In the methylation of aromatic amines special precautions are necessary to prevent condensation of the formaldehyde with the aromatic ring.1009... 

Alternatively, hydrogen cyanide and then, dropwise, the aldehyde are added to the aniline in ether, whereupon water separates in a resulting vigorous reaction. Or, if the anil is available in advance, it is simply treated with hydrogen cyanide in ether. 

Hydroformylation is a metal-catalyzed reaction in which an olefin, CO, and H react to produce an aldehyde. The reaction was discovered at BASF by Otto Roelen, and was called hydroformylation by Adkins. This transformation is also sometimes referred to as the "oxo" process. In a formal sense, the elements of formaldehyde are added across a C=C bond. Common side reactions include aUcene hydrogenation, aldehyde hydrogenation, and alkene isomerization. Hydroformylation is one of the largest volume reactions conducted with homogeneous catalysts in the chemical industry. It is used to produce over 14 billion pounds of aldehydes per year (two pounds per year for every person on Earth ). The aldehydes are converted to alcohols, acids, and other materials as useful end products. One large-volume use of hydroformylation is the conversion of propene to a mixture of -butyraldehyde and /-butyraldehyde (Equation 17.2). Since the desired product is n-butyraldehyde, a great deal of effort has been expended to maximize the n i (noimal to iso, or often also called l/b for linear to branched) ratio of aldehydes and to understand the factors that control it. 

Scheme 9.20. A different representation of Scheme 8.11. A cartoon representation of the reduction of ethanal (acetaldehyde, CH3CHO) with the cofactor, reduced nicotinamide adenine dmucleotide (NADH). The curved arrows depict the loss of a hydrogen, with its electron parr, from the nicotinamide portion of the cofactor as it is being added to the re-face of the aldehyde, thus becoming the pro-R hydrogen of the resulting alcohol. The hydrogen added in the reduction is the same hydrogen as that removed in the oxidation.

The reaction of nitroaniline and the aldehyde gives a stoichiometric amount of water (or hydrogen, since it is known that Ru3(CO)n catalyses the WGSR, e.g. [51]). The presence of water accounts for the presence of several by-products formed in small amounts [48]. At the end of run 1, new nitro compound and aldehyde were added to the solution and a second catalytic cycle was carried out (Table 8, run 2), with results almost identical to those of run 1. The same results were also obtained with a third run (run 3). In spite of the presence of water, at the end of the reaction the catalyst was recovered as the usual mixture of Ru3(CO)i2 and Ru(CO)s and no trace of Ru-H bonds was detected by IR spectroscopy. The reaction gave complete conversion of the nitro compound even on lowering the reaction time to 1 h (run 4). Only for an half an hour... 

The behavior of formaldehyde differs in some aspects from that of higher aldehydes. After adding formaldehyde, potentials below 0.1 V are established as for methanol. It was proposed [39] that the hydrogenation of formaldehyde proceeds in sulfuric acid solution only until methanol is formed. Chemisorbed species similar to those formed in the presence of methanol or formic acid are produced at open circuit [58] and by anodic oxidation [40] of formaldehyde. 

An aqueous solution of fuchsin (/7-rosaniline hydrochloride) decolorized with sodium hydrogen sulfite or with sodium sulfite becomes red-violet to blue if aldehydes are added to it. The reappearance of this color is not caused by simple oxidation to fuchsin, but represents a specific reaction of the aldehydic group —CHO. However, unsaturated aldehydes and certain aromatic aldehydes (vanillin, p-aminobenzaldehyde, p-dimethylaminobenz-aldehyde) and glyoxal do not react. According to more recent views (15), both amino groups of the fuchsinleukosulfonic acid (VI) react with the... 

The carbon-oxygen double bond of the carbonyl group is opened, and the hydrogen sulfite radical is added. An increase in temperature reverses the reaction more easily for ketones than for aldehydes. 

Oxo Synthesis. Ad of the synthesis gas reactions discussed to this point are heterogeneous catalytic reactions. The oxo process (qv) is an example of an industriady important class of reactions cataly2ed by homogeneous metal complexes. In the oxo reaction, carbon monoxide and hydrogen add to an olefin to produce an aldehyde with one more carbon atom than the original olefin, eg, for propjiene ... 

It has been frequently noted that certain lots of iron filings are not satisfactory for the reduction of heptaldehyde to heptyl alcohol in acetic acid solution. E. E. Reld and J. R. Ruhoff have found that the addition of a solution of 20 g. of nickel cliloride hexahydrate in 50 cc. of water immediately after the addition of the aldehyde will cause the reaction to start at once and wiU greatly accelerate the rate of reaction so that it is complete in two hours instead of the usual six to seven hours. The checkers have found this to be the case even with a lot of iron which could not be made to react when reduced in hydrogen. It is also recommended that the reaction mixture be divided between two 12-I. flasks and that 3 1. of water be added to each half immediately at the end of the reaction. This prevents the mixture from setting to a hard mass in case the steam distillation is not carried out at once, and also reduces the amount of foaming. 

Benzaldehyde.—The aldehydes of the aromatic seiies may also be obtained by the oxidation of a methyl side-chain with chromium oxychloride. The solid brown product, C,H,.CH.)(CrO,CL)2, formed by adding C1O2CIJ to toluene, dissolved in carbon bisulphide, is decomposed with water, and benzaldehyde sepaiates out (Etard). Other methods for pie-paring aromatic aldehydes are (i) the Fiiedel-Crafts reaction, in which a mixture of carbon monoxide and hydrogen chloride aie passed into the hydrocaibon in presence of aluminium chloride and a little cuprous chloride,... 

Reduction of unsaturated carbonyl compounds to the saturated carbonyl is achieved readily and in high yield. Over palladium the reduction will come to a near halt except under vigorous conditions (73). If an aryl carbonyl compound, or a vinylogous aryl carbonyl, such as in cinnamaldehyde is employed, some reduction of the carbonyl may occur as well. Carbonyl reduction can be diminished or stopped completely by addition of small amounts of potassium acetate (i5) to palladium catalysts. Other effective inhibitors are ferrous salts, such asferroussulfate, at a level of about one atom of iron per atom of palladium. The ferrous salt can be simply added to the hydrogenation solution (94). Homogeneous catalysts are not very effective in hydrogenation of unsaturated aldehydes because of the tendencies of these catalysts to promote decarbonylation. 

In certain reductions it is an advantage to reduce the platinum oxide to platinum black by shaking with hydrogen in the presence of solvent only, before the substance to be reduced is added to the mixture. More often the catalyst is reduced in the presence of the substance to be reduced with aldehydes for example the platinum black is usually more finely divided and generally more active if prepared in presence of the aldehyde. 

A suspension of benzene-1,2-diamine hydrochloride in MeOH saturated with hydrogen chloride was added in small portions to a stirred solution of an equimolecular amount of a /Tchlorovinyl aldehyde in the minimum amount of ice-cooled MeOH. The mixture was allowed to warm to rt, stirred for a further 30 min and the precipitated benzodiazepiniutn chloride was collected. 

---