Aldehydes alcohols, reduction

Conversion of Acid Chlorides into Alcohols Reduction Acid chlorides are reduced by LiAJH4 to yield primary alcohols. The reaction is of little practical value, however, because the parent carboxylic acids are generally more readily available and can themselves be reduced by L1AIH4 to yield alcohols. Reduction occurs via a typical nucleophilic acyl substitution mechanism in which a hydride ion (H -) adds to the carbonyl group, yielding a tetrahedral intermediate that expels Cl-. The net effect is a substitution of -Cl by -H to yield an aldehyde, which is then immediately reduced by UAIH4 in a second step to yield the primary alcohol. 

The mechanism of ester (and lactone) reduction is similar to that of acid chloride reduction in that a hydride ion first adds to the carbonyl group, followed by elimination of alkoxide ion to yield an aldehyde. Further reduction of the aldehyde gives the primary alcohol. 

Because the olefin geometry in compound 9 will most certainly have a bearing on the stereochemical outcome of the hydroboration step, a reliable process for the construction of the trans trisubsti-tuted olefin in 9 must be identified. A priori, the powerful and predictable Wittig reaction28 could be used to construct E u, [3-unsaturated ester 10 from aldehyde 11. Reduction of the ethoxycarbonyl grouping in 10, followed by benzylation of the resulting primary alcohol, would then complete the synthesis of 9. Aldehyde 11 is a known substance that can be prepared from 2-furylacetonitrile (12). 

Iridium-catalyzed transfer hydrogenation of aldehyde 73 in the presence of 1,1-dimethylallene promotes tert-prenylation [64] to form the secondary neopentyl alcohol 74. In this process, isopropanol serves as the hydrogen donor, and the isolated iridium complex prepared from [Ir(cod)Cl]2, allyl acetate, m-nitrobenzoic acid, and (S)-SEGPHOS is used as catalyst. Complete levels of catalyst-directed diastereoselectivity are observed. Exposure of neopentyl alcohol 74 to acetic anhydride followed by ozonolysis provides p-acetoxy aldehyde 75. Reductive coupling of aldehyde 75 with allyl acetate under transfer hydrogenation conditions results in the formation of homoallylic alcohol 76. As the stereochemistry of this addition is irrelevant, an achiral iridium complex derived from [Ir(cod)Cl]2, allyl acetate, m-nitrobenzoic acid, and BIPHEP was employed as catalyst (Scheme 5.9). 

Electrogenerated acid (EG acid), aldehyde to alcohol reduction, etherification, 65-69... 

Halocarbons, ketone-alcohol reduction, 84 Halogenation, 4-methylbenzyl chloride [reductive halogenation of aldehyde to benzyl chloride], 124 Hemiacetals, reduction of, 97-99 Hemiaminals, reduction of, 99-100 Hemiketals, reduction of, 97-99 Heptene derivatives, alkene to alkane reductions, disubstituted alkenes, 36-38... 

By means of this reduction process it is possible to obtain, from the corresponding aldehydes, alcohols such as trichloroethyl alcohol or cinnamyl alcohol, which are not otherwise readily accessible or are otherwise inaccessible. Tnbromoethyl alcohol ( avertin ), an important narcotic, is prepared in this way (F. F. Nord). It is given by the rectum. 

Nitrocyclohexadiene 93a reacted with 4.0 equivalents of cyclopentadiene in toluene at 110°C for 96 h, producing the 10-glyco-l-nitrotricyclo[5.2.2.02,6]undeca-3,8-diene 96a in 70% yield. Subsequent treatment with potassium carbonate in a methanol-water (9 1) solution followed by oxidative cleavage of the sugar side chain with sodium metaperiodate afforded aldehyde 96c. Reduction of the aldehyde with sodium borohydride produced alcohol 96d. 

In contrast to oxidative dechlorination, the hydrolytic dechlorination of chloramphenicol replaces a Cl-atom with a OH group to yield a (monochlo-ro)hydroxyacetamido intermediate. The latter, like the dichloro analogue, also eliminates HC1, but the product is an aldehyde that is far less reactive than the oxamoyl chloride intermediate. Chloramphenicol-aldehyde undergoes the usual biotransformation of aldehydes, namely reduction to the primary alcohol 11.41 and dehydrogenation to the oxamic acid derivative 11.40 (Fig. 11.7). 

The usual range of reactions has been recorded for the aldehydes of dibenzothiophene. Oxidation yields the corresponding acid, - reduction with LAH the corresponding alcohol, reduction under Huang-Minlon conditions the corresponding methyl compound, and two examples of the Cannizarro reaction have been described. ... 

Reduction of amides may yield aldehydes, alcohols or amines. Which of these three classes is formed depends on the structure of the amide, on the reducing agent, and to a certain extent on reaction conditions. 

Usually alcohols accompany aldehydes in reductions with lithium aluminum hydride [1104] or sodium bis 2-methoxyethoxy)aluminum hydride [544], or in hydrogenolytic cleavage of trifluoroacetylated amines [7772]. Thus terr-butyl ester of. -(. -trifluoroacetylprolyl)leucine was cleaved on treatment with sodium borohydride in ethanol to rerr-butyl ester of A7-prolylleucine (92% yield) and trifluoroethanol [7772]. During catalytic hydrogenations over copper chromite, alcohols sometimes accompany amines that are the main products [7775]. 

Cathodic surfaces of finely divided platinum, palladium and nickel have a low hydrogen overvoltage and the dominant electrochemical reaction is the generation of a layer of hydrogen atoms. The electrocatalytic hydrogenation of aldehydes and ketones can be achieved at these surfaces. Cathodes of platinum or palladium black operate in both acid solution [203] and in methanol containing sodium methoxide [204], The carbonyl compound is converted to the alcohol. Reduction of 4-tert-butylcyclohexanone is not stereoselective, however, 1,2-diphenylpropan-l-one is converted to the / reo-alcohol. 

Furfural. Furfural is readily obtainable from dehydration of pentoses. Reduction of furfural can lead to a variety of products that are more volatile, more stable and possibly also more useful than furfural itself. Selective reduction of the aldehyde moiety leads to furfuryl alcohol (Scheme 15), whereas further reduction of the furan core will lead to tetrahydrofurfuryl alcohol. Reductive deoxygenation can result in the formation of either 2-methylfuran or 2-methyltetrahydrofuran, which can be used as liquid fuels or solvents. 

Preparation of the Aldehyde 2 The absolute configuration of the iriene aldehyde 2 was set by Noyori hydrogenation of ethyl butyrylacetate S. Silylation and Dibal reduction then gave the aldehyde 6. Reduction of the homologated ester gave the alcohol, which was oxidized to the desired aldehyde 7 by the Swem procedure. Condensation of 7 with the Wollenberg stannyl diene followed by deprotection then gave the unstable aldehyde 2. 

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