Conversion of Imines into Aldehydes and Ketones

Apparatus 11, three-necked, round-bottomed flask, equipped with a dropping funnel, a mechanical stirrer and a thermometer. 

Aldimines and ketimines react with an excess of aqueous acid to give solutions of iminium salts C=NHR. When the pH is sufficiently low ( 4), these solutions remain unchanged at room temperature. Upon heating, aldehydes or ketones are liberated. This hydrolytic process is accelerated by increasing the pH, the optimal rate being reached at pH (V 6 [IX 

In the usual procedure, the hydrolytic cleavage is carried out with oxalic acid, sometimes very diluted [2], We found it more convenient to dissolve the imine in a cold ( 0°C) aqueous solution of a 10 to 20 mol% excess of hydrochloric acid. Impurities (if present) may be removed by extracting the cold acidic solution (pH 2) with Et20 or pentane. The pH of the aqueous solution is then brought at 5.5 to 6 by controlled addition of an aqueous solution of potassium carbonate, after which the solution is heated. 

Dauben WG, Beasley GH, Broadhurst MD, Muller B, Peppard DJ, Pesnelle P, Suter C (1975) J Am Chem Soc 97 4973 

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