Primary alcohols aldehydes from

ALDEHYDES FROM PRIMARY ALCOHOLS BY OXIDATION WITH CHROMIUM TRIOXIDE 1-HEPTANAL, 52, 5 ALDEHYDES FROM sym-TRITHIANE n-PENTADECANAL, 51, 39 Aldehydes, acetylenic, 54, 45 Aldehydes, aromatic, 54, 45 Aldehydes, benzyl, 54, 45 Aldehydes, olefinic, 54, 45... 

ALDEHYDES FROM PRIMARY ALCOHOLS BY OXIDATION WITH CHROMIUM TRIOXIDE 1-HEPTANAL... 

The oxidation procedure used here is also applicable to the preparation of aldehydes from primary alcohols. 

The activation of DMSO by electrophilic reagents such as oxallyl chloride or trifluoroacetic anhydride (TFAA) (among many others) produces an oxidant capable of oxidizing primary alcohols to aldehydes in high yields. This oxidation is called the Swern oxidation and yields the aldehyde (oxidized product) by reductive elimination of dimethylsulfide (reduced product) and proceeds under mild, slightly basic conditions. It is a second widely used and effective oxidative method for the production of aldehydes from primary alcohols. 

A common step in the metabolism of alcohols is carried out by alcohol dehydrogenase enzymes that produce aldehydes from primary alcohols that have the -OH group on an end carbon and produce ketones from secondary alcohols that have the -OH group on a middle carbon, as shown by the examples in Reactions 7.3.6 and 7.3.7. As indicated by the double arrows in these reactions, the reactions are reversible and the aldehydes and ketones can be converted back to alcohols. The oxidation of aldehydes to carboxylic acids occurs readily (Reaction 7.3.8). This is an important detoxication process because aldehydes are lipid soluble and relatively toxic, whereas carboxylic acids are more water soluble and undergo phase n reactions leading to their elimination. 

The 1-hydroxyethyl radical may be further oxidized, to form aldehydes from primary alcohols, and ketones from secondary alcohols. The only tertiary alcohol to he studied in detail gave the corresponding ketone on irradiation. 

Many of the oxidants employed to prepare aldehydes from primary alcohols may be used to further oxidize the aldehyde initially formed to the corresponding carboxylic acid. The most common oxidants for this purpose include KMn04," chromic acid, sodium chlorite,silver oxide," and PDC in DMF. °... 

Another objection to the theory may be based on the experimental data existing on alcohol oxidation. According to Bone, alcohols should oxidize through a dihydroxy compound by the addition of an oxygen atom. The work of Wieland 5 and others has shown that the formation of aldehydes from primary alcohols may take place by dehydrogenation rather than further hydroxylation. Experimental evidence is lacking for the formation of the simple glycols by alcohol oxidation. 

The mild reaction conditions of the Corey-Kim oxidation reaction make it an excellent choice when the oxidation of an alcohol that is contained within a complex synthetic intermediate is needed. Rapoport has shown this oxidation method to be useful to prepare aldehydes from primary alcohols in several multi-step syntheses. For example, treatment of alcohol 26 with NCS and DMS in toluene provided aldehyde 27 that was ultimately used to construct the (-)-enantiomer of the C-9-amino acid constituent (28) of immunosuppressant drug cyclosporine as well as the naturally occurring (+)-enantiomer after a slight modification.6... 

Jones s oxidation is a powerful oxidizing medium for the conversion of alcohols to ketones. Unfortunately, this is such a powerful oxidizing medium that unwanted products are possible due to overoxidation. When a primary alcohol such as 1-pentanol (15) reacts with chromium trioxide and aqueous sulfuric acid, it follows the same mechanistic pathway as 9, with formation of chromate ester 16. However, experiments show that the yields of aldehyde from primary alcohols can be very low. 1-Propanol is oxidized to propanal, for example, in only 49% yield, and to obtain the product requires a short reaction time. Very often, a carboxylic acid is formed as a second product or even the major oxidation product rather than the aldehyde. It is known that aldehydes are easily oxidized to carboxyhc acids, even by oxygen in the air. If a sample of butanal were spilled, for example, it is rapidly oxidized to butanoic acid by air. This oxidation is easily detected as the sharp butanal smell is replaced by the pungent butanoic acid smell. Butanoic acid is found in rancid butter and in dirty feet, for example. 

Like PDC and PCC, dimethyl sulfoxide in the presence of oxalyl chloride and trimethylamine gives aldehydes from primary alcohols and ketones from secondary alcohols. 

Polymer-bound oxidizing agents, such as chromium(VI) species, have many applications. Chromium in all oxidation states has been identified as carcinogenic. Poly(vinylpyridinium dichromate) (25) in cyclohexane at 70 °C gave high yields of aldehydes from primary alcohols, as in... 

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