Manganese dioxide/sodium cyanid

Manganese dioxide sodium cyanide acetic acid Carboxylic acid esters from aldehydes s. 24,177... 

Manganese dioxide sodium cyanide Carboxylic acid amides from aldehydes... 

Aldehyde 244 reacts with manganese dioxide and sodium cyanide in ethanol to give ethyl ester 245 (Scheme 19), while oxidation of alcohol 12 with sodium peroxodisulfate in the presence of a catalytic amount of ruthenium chloride furnishes the carboxylic acid 246 (Scheme 19) <1998CPB287>. 

Intimate mixtures of chlorates, bromates or iodates of barium, cadmium, calcium, magnesium, potassium, sodium or zinc, with finely divided aluminium, arsenic, copper carbon, phosphorus, sulfur hydrides of alkali- and alkaline earth-metals sulfides of antimony, arsenic, copper or tin metal cyanides, thiocyanates or impure manganese dioxide may react violently or explosively, either spontaneously (especially in presence of moisture) or on initiation by heat, friction, impact, sparks or addition of sulfuric acid [1], Mixtures of sodium or potassium chlorate with sulfur or phosphorus are rated as being exceptionally dangerous on frictional initiation. 

Conjugated—a,/)-unsaturated or aromatic—aldehydes are oxidized by manganese dioxide in the presence of one equivalent of sodium cyanide to give an acyl cyanide (Formula C in Figure 17.18) via an intermediate cyanohydrin (B in Figure 17.18), which is also either an allylic or a benzylic alcohol. Alcohols of this kind can be oxidized by a relatively weak oxi-... 

Carboxylic amides. Gilman has extended the procedure of Corey et at. (2, 261) for oxidation of allylic alcohols to carboxylic esters to the preparation of carboxylic amides. Thus oxidation of aromatic and a,/ -unsaturated aldehydes with Mn02 in the presence of sodium cyanide and an amine gives the corresponding carboxylic amides in high yield. In the absence of sodium cyanide, high yields of nitriles are formed from aldehydes, ammonia, and manganese dioxide. 

A different type of ester formation takes place when a,(3-unsaturated alcohols are oxidized with manganese dioxide and subsequently treated with sodium cyanide, acetic acid, manganese dioxide, and methanol. The final result is shown by the sequence of reactions in equation 238 [382]. 

A somewhat similar oxidation takes place when an aldehyde is treated with sodium cyanide and manganese dioxide or argentic oxide [382], The reaction is assumed to proceed through a cyanohydrin, which is oxidized to an a-keto nitrile. The a-keto nitrile in turn is converted into an acid (by argentic oxide in methanol) or an ester (by manganese dioxide in methanol). The method is especially suited for a, -unsaturated aldehydes [382] (equation 354). 

The oxidation of aldehydes in the presence of amines occurs at low temperatures with nickel perox-ide. Similarly, the oxidation of aromatic aldehydes with manganese dioxide or ruthenium chloride in the presence of sodium cyanide and an amine leads to the corresponding amides. 

A direct method for conversion of aldehydes to esters has been reported. It is applicable to a,j8-unsaturated aldehydes and aromatic aldehydes. The process involves stirring the aldehyde for several hours with sodium cyanide and manganese dioxide in a solution of methanol containing some acetic acid. The product is the methyl ester of the a,j8-unsaturated or aromatic carboxylic add. Indicate the basis for the success of this procedure. 

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