Aldehydes from formates

Acetaldehyde [75-07-0] (ethanal), CH CHO, was first prepared by Scheele ia 1774, by the action of manganese dioxide [1313-13-9] and sulfuric acid [7664-93-9] on ethanol [64-17-5]. The stmcture of acetaldehyde was estabhshed in 1835 by Liebig from a pure sample prepared by oxidising ethyl alcohol with chromic acid. Liebig named the compound "aldehyde" from the Latin words translated as al(cohol) dehyd(rogenated). The formation of acetaldehyde by the addition of water [7732-18-5] to acetylene [74-86-2] was observed by Kutscherow] in 1881. 

Nitro alcohols form salts upon mild treatment with alkahes. Acidification causes separation of the nitro group as N2O from the parent compound, and results in the formation of carbonyl alcohols, ie, hydroxy aldehydes, from primary nitro alcohols and ketols from secondary nitro alcohols. 

EHRLICH - SACHS Aldehyde Synthesis Formation of o-nitrobenzaldehydes from o-nitrotoluenea. 

Alkyl radicals, R, react very rapidly with O2 to form alkylperoxy radicals. H reacts to form the hydroperoxy radical HO2. Alkoxy radicals, RO, react with O2 to form HO2 and R CHO, where R contains one less carbon. This formation of an aldehyde from an alkoxy radical ultimately leads to the process of hydrocarbon chain shortening or clipping upon subsequent reaction of the aldehyde. This aldehyde can undergo photodecomposition forming R, H, and CO or, after OH attack, forming CH(0)00, the peroxyacyi radical. 

Acetaldehyde.—The formation of aldehyde from alcohol probably occtiis by the Liddition of oxygen and bubsetpiem ciimination of water,... 

Kelly applied this chemistry to the synthesis of cyclosexipyridine 66. This is an example of an intramolecular variation to this method. Masked enal 65 was prepared and treated with the standard reagents. The acidic medium liberated the aldehyde from its acetal protection. This in situ formation of the reactive species, similar to the above example, then undergoes cyclization to the expected pyridine derivative 66. 

Packer and Richardson (1975) and Packer et al. (1980) made use of the fact that electrons can be generated in water by y-radiation from a 60Co source (Scheme 8-29) to induce a free radical chain reaction between diazonium ions and alcohols, aldehydes, or formate ion. It has to be emphasized that the radiolytically formed solvated electron in Scheme 8-29 is only a part of the initiation steps (Scheme 8-30) by which an aryl radical is formed. The aryl radical initiates the propagation steps shown in Scheme 8-31. Here the alcohol, aldehyde, or formate ion (RH2) is the reducing agent (i.e., the electron donor) for the main reaction. The process is a hydro-de-diazoniation. 

Motoda, S., Formation of aldehydes from amino acids by polyphenol oxidase, J. Ferment Technol., 57, 395, 1979. (CA92 17776e)... 

Another factor complicating the situation in composition of peroxyl radicals propagating chain oxidation of alcohol is the production of carbonyl compounds due to alcohol oxidation. As a result of alcohol oxidation, ketones are formed from the secondary alcohol oxidation and aldehydes from the primary alcohols [8,9], Hydroperoxide radicals are added to carbonyl compounds with the formation of alkylhydroxyperoxyl radical. This addition is reversible. 

As mentioned in the introduction, hydroformylation is an important industrial process used for the formation of aldehydes from alkenes. Some six million... 

Carbanions, generated by the reaction of benzylsilanes with tetra-n-butylammo-nium fluoride react with non-enolizable aldehydes to produce the alcohol [67], When a stoichiometric amount of the ammonium fluoride is used, the methylarene corresponding to the benzylsilane is frequently a by-product and arises from formation of the hydrogen difluoride salt during the reaction. When only catalytic amounts of the ammonium fluoride initiate the reaction, the formation of the methylarene is suppressed. In a similar type of reaction (although the mechanism is not known) between aldehydes and ketones, allyl bromide, and tin in the presence of trimethylsilyl chloride the yield of the but-l-en-4-ol is raised significantly by the addition of tetra-n-butylammonium bromide, particularly in the reactions with... 

A viable iron carbonyl-mediated reduction process converts acid chlorides and bromoalkanes into aldehydes [3, 6]. Yields are high, with the exception of nitro-benzoyl chloride, and the procedure is generally applicable for the synthesis of alkyl, aryl and a,(i-unsaturated aldehydes from the acid chlorides. The reduction proceeds via the initial formation of the acyl iron complex, followed by hydride transfer and extrusion of the aldehyde (cf. Chapter 8). 

Recently proof has been reported for a heterometallic bimolecular formation of aldehyde from a manganese hydride and acylrhodium species [2], Phosphine free, rhodium carbonyl species show the same kinetics as the cobalt system, i.e. the hydrogenolysis of the acyl-metal bond is rate-determining. Addition of hydridomanganese pentacarbonyl led to an increase of the rate of the hydroformylation reaction. The second termination reaction that takes place according to the kinetics under the reaction conditions (10-60 bar, 25 °C) is reaction (3). The direct reaction with H2 takes place as well, but it is slower on a molar basis than the manganese hydride reaction. 

Aldehydes react with dimethyl 2-phenylselenofumarate (70) at -70 °C in diethyl ether in the presence of MeLi to give good yields of highly substituted 4-phenylselenobutano-y-lactones (71) and (72). High diastereoselectivity [for benzaldehyde, (71) (72)-89 11] was rationalized by assuming the formation of a chelated intermediate between MeLi and (70), with approach of the aldehyde from the favoured si-fact (Scheme 5). " ... 

The S-configurated nucleophilic reagent 41 preferentially adds to the aldehyde from the Re face (ul topicity), and the predominant or almost exclusive formation of the diastereomers 146 results (Scheme 20). The reaction of 5 -41 with enantiomericaUy pure S-configurated aldehydes leads to the products 146c-e in high diastereoselectivity as well, thus suggesting the assumption of a matched pair in this combination of enantiomericaUy pure starting materials (see below) . ... 

In the absence of alkoxyl radicals and the formation of acetals, the aldehyde from the ring opening of 107 undergoes further reaction, to form furanones. Seydel and coworkers212 isolated a chromophore (A.max 261 nm) from the reaction of 2-deoxy-D-erythro-pentose in... 

These results indicate that the same crystalline face does not necessarily exhibit the same catalytic properties with different molecules. Thus, the (010) face of a-Mo03 is selective for the formation of aldehydes from alcohols while it promotes essentially the deep oxidation of olefins. It is expected that the studies on structure-sensitive reactions will be made more quantitative using recent methods to determine the number of surface M=0 species (425 —7). It should be noted that the earlier observation on the specificity of Mo03 crystalline faces in propylene oxidation has been obtained on oriented Mo03-graphite catalysts (425k). Non-structure-sensitive reactions have also been reported (425k). 

Isatin has been used in the Strecker degradation of a-amino acids to aldehydes,434-437 and in the formation of benzaldehydes from benzyl-amines.431,435,438-440 These conversions have been the subject of a review, and mechanisms have been proposed.441 This formation of aldehydes from primary amines may, in part, explain some of the... 

Another important class of cycloaddition reactions is the formation of oxetane rings between a photoexcited carbonyl compound and an unsaturated molecule. These reactions also occur probably through an exciplex although these exciplexes are non-fluorescent as they are formed from the triplet state of the ketone or aldehyde. The formation of the four-membered oxetane ring is an interesting example of a typical photochemical reaction... 

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