Carboxylic acids with ammonium polysulfide

The Willgerodt reaction, which involves heating ketones with ammonium polysulfide, is the most important route to carboxylic acids without degradation of the carbon chain. It applies especially to methyl and alkyl... 

Willgerodt reaction. In its original form this reaction involved heating an aryl alkyl ketone in a sealed tube at 210-230° with an aqueous solution of yellow ammonium polysulfide, prepared by dissolving sulfur in ammonium sulfide solution. The product is an aryl substituted aliphatic aciil amide, together with some of the corresponding carboxylic acid and often the hydrocarbon. An example is the... 

Ammonium polysulfide Carboxylic acid amides from a-subst. carboxylic acids Degradation with loss of 1 G-atom... 

The name of Conrad Willgerodt is associated with a group of closely related reactions which have as a common feature the conversion of a carbonyl compound into an amide mth the same number of carbon atoms. The original process involved the reaction of an appropriately substituted alkyl aryl ketone with an aqueous solution of yellow ammonium polysulfide at an elevated temperature to form an aiyl-substituted aliphatic acid amide, ti ether with a smaller amount of the corresponding ammonium salt of the carboxylic acid. An example is the conversion of acetophenone into phenylacetamide and ammonium phenylacetate. ... 

The Kindler variation, - which promises to be more useful than the original Willgerodt procedure, consists in heating the ketone with approximately equimolecular amounts of sulfur and a dry amine instead of aqueous ammonium polysulfide. A thioamide is formed as the principal product and on hydrolysis with acid or alkali affords the carboxylic acid, usually in good yield. Generally a secondary aliphatic amine but sometimes a primary amine or even anhydrous ammonia is used the development of a method for the electrolytic reduction of the thioamides to amines extended the usefulness of the reaction as a new route to the synthesis of many important nitrogen bases. Early descriptions of this... 

It is of interest to note the behavior of molecules containing other functional groups. Carbinols form amides at somewhat higher tanpera-tures than the corresponding ketones, probably by way of unsaturated intermediates. Aldehydes are converted into the corresponding carboxylic acid amides when heated with aqueous ammonium polysulfide, > and they form substituted thioamides under conditions of the Kindler procedure. Aldimines likewise are converted to acid derivatives. Two imineS derived from methyl ketones and methylamine are reported to react with sulfur to form N-methylarylthioacetamides in a manner analogous to the reaction of methyl ketones in the presence of the amine. 

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