Wolf-Kishner reaction

A correlation of voacoline with voacarpine was carried out on a small scale, with thin-layer chromatography an important tool for following the reactions. Voacoline was refluxed in benzene with potassium tertiary butylate to yield a complex mixture containing IX (positive iodoform reaction) which was esterified and subjected to a Wolf-Kishner reaction. From the products of this reaction a- and jS-dihydrodehydroxymethyl-voachalotine (X C-20 epimers) were recognized by thin-layer chromatography. 

The absolute configuration of vincamine and hence the other eburn-amine alkaloids has been accomplished by showing that the optical rotatory dispersion curve of ( —)-l,l-diethyl-l,2,3,4,6,7,12,12b-octa-hydroindolo[2,3a]quinolizine (XVI) (mp 105°-106°) obtained by a Wolf-Kishner reaction on (— )-eburnamonine was enantiomeric with (-I-)-l,2,3,4-tetrahydroharman (XVII) (24). The i -configuration has to be ascribed to the latter compound because it has been converted into V-carboxyethyl-D-alanine (XVIII) of known absolute configuration (24). This work, with the exception of the Schizozygia alkaloids, establishes the absolute configurations of the eburnamine alkaloids since they have all been interrelated. 

The Wolf-Kishner reaction is the reduction of carbonyl groups to methylene groups by base-catalyzed decomposition of the hydrazone of the carbonyl compound. Alkyldiimides are believed to be formed and then collapse with loss of nitrogen. 

The preparation of long-chain fatty acids has been carried out in this way because cleavage of 115 with strong sodium hydroxide gives the ketoacid (116), which is easily reduced by the Wolf-Kishner method to the saturated acid. A similar sequence of reactions can be carried out starting with the cyclopentanone enamine, and this method allows lengthening the chain... 

Wittig reaction -selective 108 Wolf-Kishner reduction (see ketone to methylene)... 

A slightly more vigorous method, known as the Wolf-Kishner reduction, is driven by the elimination of nitrogen gas from a hydrazone. Hot concentrated sodium hydroxide solution deprotonates the hydrazone, which can then eliminate an alkyl anion—a reaction you would usually be wary of writing, but which is made possible by the thermodynamic stability of N2. 

Acyl products that are formed can be reduced by reactions such as Clemmenson or Wolf-Kishner reductions. 

The carbonyl groups of aldehydes and ketones can be converted to methylene groups by Clemmenson and Wolf-Kishner reduction reactions. 

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