Wieland degradation of carboxylic acids

Bam mane ware, 25, 72, 97 Barbier Wieland, degradation of carboxylic acid by method of, 24,38,41 Barbituric acid, 21, 5 Barium carbonate, 22, 86 Barium chloride, 23, 17 Barium hydroxide, 22, 87, 91, 25, 75, 27, 1... 

In acid media, for example, in chromic acid in sulfuric acid, tertiary alcohols that can suffer dehydration form cilkenes, which are degraded to ketones and carboxylic acids Barbier-Loquin and Wieland degradation of carboxylic acids) 1150 (equation 273). 

Barbier-Wieland degradation. Stepwise carboxylic acid degradation of aliphatic acids (particularly in sterol side chains) to the next lower homo log. The ester is converted to a tertiary alcohol that is dehydrated with acetic anhydride, and the olefin oxidized with chromic acid to a lower homologous carboxylic acid. 

Carboxylic acids from ethylene derivatives Barbier-Wieland degradation of bile acids... 

Barbier-Wieland degradation of steroid carboxylic acids Ethylene derivatives from carboxylic acids... 

This procedure, coupled with the procedure described on p. 41, illustrates the Barbier-Wieland method for systematically degrading carboxylic acids. foxwor-Desoxycholic acid may be prepared from wor-desoxycholic acid by repetition of this procedure. If the chromic acid oxidation product is not sufficiently solid to filter after dilution with water, the mixture must be extracted with ether and washed with dilute hydrochloric acid before the alkaline extraction. Wxwor-Desoxycholic acid may be crystallized from ethyl alcohol. It melts at 239-241°. 

MIESCHER DEGRADATION. Adaptation of the Barbier-Wieland carboxylic acid degradation to pcrmil simultaneous elimination of three carbon atoms, as in degradation of the bile acid side chain to the methyl ketone stage. Conversion of the methyl ester of the bile acid to the tertiary alcohol, followed by dehydration, bromination. dehydrohalogenatinn, and oxidation of the diene yields die required degraded ketone. 

Synthesis from Steroidal and Alkaloidal Intermediates Steroidal intermediates have been employed in the synthesis of certain alkaloids such as dihydroconessine (58)(ref.55), one of the 3-aminoconanine bases, from the bile acid compound 3-B-acetoxybisnorcholenic acid, a substance obtained from appropriately-protected coprostanol by oxidation and two Barbier-Wieland degradations. The method consisted in converting the carboxyl into a formylamino group, the acetoxy into a tosylate which was then substituted by a dimethylamino group, reduction of the formylamino to methylamino and formation of the five-membered ring E by... 

Three carbon degradation of a carboxylic acid side chain (see Barbier-Wieland) (see 1st edition). 

A fairly straightforward scheme, called the Barbier-Wieland degradation, was at that time used for determining the number of carbon atoms in an ahphatic acid fragment. This involves first converting the carboxylic acid 11-1 to the corresponding ester 11-2 (Scheme 1.11). Reaction of the ester with phenylmagnesium bromide leads to carbinol 11-3. Treatment with acid leads to dehydration and formation of the olefin 11-4. Oxidation by one of several methods cleaves... 

In the Barbier-Wieland degradation, the alpha-methylene group in an aliphatic carboxylic acid is removed in a sequence of reaction steps, effectively a chainshortening. The inverse procedure is the Amdt-Eistert synthesis, where an acid is converted into acyl halide and reacts with diazomethane to give the highest homolog. 

Synthesis of ethylene derivatives from carboxylic acid esters Modified Barbier Wieland degradation... 

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