ALDEHYDES BY OXIDATION

Oxidations and reductions are amongst the most frequent in situ prechromato-graphic reactions they were exploited as early as 1953 by Miller and Kirchner [9]. They characterized citral as an aldehyde by oxidizing it to geranic acid and reducing it to geraniol. Further examples are listed in Table 10. 

ALDEHYDES BY OXIDATION OF TERMINAL OLEFINS WITH CHROMYL CHLORIDE 2,4,4-TRIMETHYL-PENTANAL, 51, 4 ALDEHYDES FROM ACID CHLORIDES BY MODIFIED ROSENMUND REDUCTION 3,4,5—TRIMETHOXYBENZ-ALDEHYDE, 51, 8 ALDEHYDES FROM ACID CHLORIDES BY REDUCTION OF ESTER MESYLATES WITH SODIUM BOROHY-DRIDE CYCLOBUTANECARBOXAL-DEHYDE, 51, 11... 

ALDEHYDES BY OXIDATION OF TERMINAL OLEFINS WITH CHROMYL CHLORIDE 2,4,4-TRIMETHYLPENTANAL... 

Aldehydes by Oxidation of Terminal Olefins with Chromyl Chloride... 

Preparation of a A"-Urethane Protected a-Amino Aldehyde by Oxidative Methods... 

Table 4 Preparation of N°-Protected a-Amino Aldehydes by Oxidation of P-Amino Alcohols 1032-37-42 ...

The reduction product, 11, can be converted to an aldehyde by oxidation with aqueous hydrogen peroxide, provided the pH is carefully controlled. (Remember, aldehydes are unstable in strong base.)... 

H. Bomowski, D. Dopp, R. lira, U. Langer, H. Offermans, K. Praefcke, G. Prescher, G. Simchen, D. Schumann, Preparation of Aldehydes by Oxidation, in Methoden Org. Chem. (Houben-Weyl) 4th ed., 1952-, Aldehydes (J. Falbe, Ed.), Bd. E3, 231, Georg Thieme Verlag, Stuttgart, 1983. 

Aldehyde synthesis. An aldehyde synthesis involves addition of an alkyllithium to 1 in the presence of TMEDA to give l-phenylthio-l-trimethylsilylalkanes (2), which are converted to aldehydes by oxidation, rearrangement, and hydrolysis (10, 314). 

For example, oxidation of acenaphthene by red lead in acetic acid gives 7-acenaphthenol acetate, from which 7-acenaphthenol is obtained by saponification with methanolic sodium hydroxide. Phenols may be prepared indirectly from aromatic aldehydes by oxidation with peracetic acid followed by hydrolysis of the resulting aryl formate. "... 

From alcohols or aldehydes by oxidation as previously discussed. 

The (3-methyl homoallylic alcohol moiety of both anti- and 5yn-configurations is a characteristic structural element of a number of macrolides and polyether antibiotics. Reactions of crotylmetal (2-butenylmetal) reagents with carbonyl substrates provide access to acyclic stereo- and enantioselective syntheses of p-methyl homoallylic alcohols. The alkene moiety of these alcohols can be further elaborated into aldehydes by oxidative cleavage of the double bond, leading to aldol-type products. 

In the case of X = CO2H (Scheme 41) the product of the rearrangement is an unsaturated a-hydroxy-carboxylic acid which may be converted to an aldehyde by oxidation, thus allowing a stereoselective synthesis of (3,7-unsaturated aldehydes (Scheme 43). °... 

Despite the fact that hydrocarboxylation is a one-step synthesis to alkanoic acids and that with specific catalysts and under certain reaction conditions the straight-chain/branched-chain isomer n/i) ratio can be rather high, this route to carboxylic acids is not used commercially today. It will be up to future R D workers to design catalysts that are active and stable enough to replace today s commercial two-step synthesis for the preparation of alkanoic acids from their aldehydes by oxidation. 

Tert-butanol and 1-propanol were chosen because a marked difference in reactivity between the two alcohols was expected a priori. Transition metal oxides may also catalyze the formation of ketones or aldehydes by oxidative dehydrogenation providing they have a significant number of basic/acid site pairs [10], With both HY and WZ, the alcohol dehydration to ether and oxidative dehydrogenation pathways were essentially negligible. 

Akabori amino acid reactions. (1) Formation of aldehydes by oxidative decomposition of a-amino acids when heated with sugars. (2) Reduction of a-amino acids and esters by sodium amalgam and ethanolic hydrochloric acid to the corresponding a-amino aldehydes. (3) Formation of alkamines by... 

To date, few reports on synthetic enzymatic oxidations of aldehydes have been published. Preparative applications reported include bioconversions of natural products such as retinal (Fig. 16.4-1 A) and various aliphatic and unsaturated aldehydes (Fig. 16.4-1 B). A broad range of aromatic acids can be obtained from their corresponding aldehydes (Fig. 16.4-1 C). Another reported reaction type is the production of olefins from aldehydes by oxidative removal of formic acid from the substrate (Fig. 16.4-1 D). 

Alcohols can also be prepared by reducing aldehydes. This reaction is the reverse of that by which primary alcohols are converted into aldehydes by oxidation. As a consequence, primary alcohols are obtained. When aldehyde is treated with sodium amalgam, or a mixture of aldehyde vapor and hydrogen is passed over finely divided nickel, alcohol is formed —... 

The manufacture of acetic acid from aldehyde by oxidation with air in the presence of a catalyst has already been noted (108). The aldehyde is readily oxidized electrolytically when it is placed in the anode compartment of a cell. This method of oxidizing organic compounds is eflScient, and involves the formation of no by-products from the oxidizing agent it is being studied carefully and has been applied to the preparation of a number of organic compounds in all probability its use will be extended. 

Tollen s test is a characteristic criteria for detecting aldehydes by oxidation. The final products include a silver mirror which can be observed as a sign of the aldehyde s presence. If the compound is not an aldehyde, there is no reaction. The reaction mechanism is shown below. 

Fehling s test A chemical test for aldehydes by oxidation to a carboxylic acid and Ibrmaiion of cuprous oxide, a red precipitate. 

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