Aliphatic aldehydes, oxidation

Fehling s solution. Aqueous solutions of aliphatic aldehydes are almost invariably acidic owing to atmospheric oxidation, and therefore... 

A characteristic property of an aldehyde function is its sensitivity to oxidation A solu tion of copper(II) sulfate as its citrate complex (Benedict s reagent) is capable of oxi dizing aliphatic aldehydes to the corresponding carboxylic acid... 

Acylation. Aliphatic amine oxides react with acylating agents such as acetic anhydride and acetyl chloride to form either A[,A/-diaLkylamides and aldehyde (34), the Polonovski reaction, or an ester, depending upon the polarity of the solvent used (35,36). Along with a polar mechanism (37), a metal-complex-induced mechanism involving a free-radical intermediate has been proposed. 

The a-hydroxy hydroperoxides obtained by the above reacbon (equation 61) can oxidize highly fluonnated aliphatic aldehydes [70] (equation 62)... 

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... 

Investigation of the oxidation of aliphatic aldehydes has been confined to ew-diols which behave as secondary alcohols, being most easily oxidised in the anionic forms, e.g. 

The simple cleavage of lactones 1 or 2 with alcohol and acid has not been reported. However, when 1 is treated with benzaldehyde diethyl acetal and hydrochloric acid, ethyl 3,5 4,6-di-0-benzylidene-L-gulonate (47) is formed in >90% yield.77,78 No other isomers were observed, and other acetals of benzaldehyde, as well as aliphatic aldehydes, afford similar products in good yield.77 D Addieco prepared36 similarly protected derivatives of L-gulonic acid by oxidation of l,3 2,4-di-0-ethylidene-D-glucitol (15), followed by esterification of the resulting acid with diazomethane. 

Luciferase from bacterial sources catalyses the oxidation of long chain aliphatic aldehydes and requires the coenzyme FMN. The wavelength of the emitted radiation in this reaction is approximately 490 nm ... 

There is a limited amount of information on the extent of hydration of aldehydes in deuterium oxide. Gruen and McTigue (1963a) concluded that for five aliphatic aldehydes at 25° C is 16 % to 26 % smaller in D2O... 

Complex (1) is a catalyst for selective oxidation of benzylic, allylic alcohols to aldehydes, and secondary alcohols to ketones using r-butyl hydroperoxide. Primary aliphatic alcohol oxidation failed. The use of cumyl hydroperoxide as radical probe discounted the involvement of i-BuO /t-BuOO. Hammett studies p = -0.47) and kinetic isotope effects kn/ku = 4.8) have been interpreted as suggesting an Ru—OO—Bu-i intermediate oxidant. 

Oxidation of aliphatic aldehydes in methanol with potassium iodide as mediator follows a reaction path like that of the saccharides. The corresponding carboxylic... 

A mild one-pot procedure based on a platinum-catalyzed diborylation of 1,3-butadienes (see Eq. 30) gives doubly allylic boronate 144, which adds to an aldehyde to form a quaternary carbon center in the intermediate 145 (Eq. 105). The use of a tartrate auxiliary in this process leads to good levels of enantiose-lectivity in the final diol product, which is obtained after oxidation of the primary alkylboronate intermediate. Although examples of aliphatic, aromatic, and unsaturated aldehydes have been described, enantioselectivities vary widely (33 to 74% ee), and are good only for aliphatic aldehydes. An intramolecular variant of this interesting tandem reaction is also known. ... 

The oxidation of 2-ethylhexan-l-ol to 2-ethyl-hexanal by the Oppenauer oxidation with aliphatic aldehydes such as acetaldehyde, propionaldehyde, and isobutyr-aldehyde has been investigated with gas-phase reactants and MgO as the catalyst (196). Reaction with propionaldehyde was found to be an effective synthetic route for 2-ethylhexanal preparation, whereas with acetaldehyde and isobutyraldehyde a gradual catalyst deactivation in a flow reactor was observed. 

In contrast, the oxidation of oxadiazolines (method S) can be used to synthesize oxadiazoles from aromatic amidoximes and aliphatic aldehydes. 

Products of the LOX pathway or compounds formed by autoxidation of fatty acids (Scheme 7.2) are also important for leek aroma [31, 163]. Volatile compounds of the LOX pathway are not pronounced in the aroma profile of freshly cut leeks owing to a high content of thiosulfinates and thiopropanal-S-oxide [30]. In processed leeks that have been stored for a long time (frozen storage), however, these aliphatic aldehydes and alcohols have a greater impact on the aroma profile owing to volatilisation and transformations of sulfur compounds [31, 165]. The most important volatiles produced from fatty acids and perceived by GC-O of raw or cooked leeks are pentanal, hexanal, decanal and l-octen-3-ol (Table 7.5) [31, 35, 148, 163, 164]. 

The utility of the method was demonstrated with a variety of electron-rich and electron-poor aryl aldehydes, but the method was not suitable for aliphatic aldehydes. No racemization was observed in the copper-catalyzed oxidative amidation reaction when an optically active amine, (S)-valine methyl ester, was employed. 

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