Replacement of nitrogen by carbonyl-oxygen

Oxygen can be substituted for the nitrogen of the functional groups of nitriles, primary and secondary aliphatic nitro compounds, and often of aliphatic amines, a number of very usable methods having been worked out, of which many are generally applicable. 

It is preparatively important that aldehydes and ketones can be regenerated by hydrolytic processes from their nitrogenous condensation products such as oximes, phenylhydrazones, semicarbazones, and SchifF bases. 

Reaction of nitriles with dry hydrogen chloride in anhydrous ether or in an ether-chloroform mixture affords imidoyl chlprides which are reduced by stannous chloride to products that afford aldehydes on hydrolysis. The method seems to be generally applicable only to aromatic and heterocyclic aldehydes the activity of the stannous chloride used for the reduction seems to be the most important factor in the reaction.580 2-Naphthaldehyde has been synthesized580 in 95% yield by this method, and 4-methyl-5-thiazolecarbaldehyde in 40% yield.581 

A similar conversion of nitriles into aldehydes has been reported by Henle.582 He used sodamide in place of stannous chloride and added phenylhydrazine to the mixture this led to phenylhydrazones that were cleaved to the aldehydes in the usual way. 

A simple method of preparing aldehydes is to trap the aldehydes formed as intermediates in the catalytic hydrogenation of nitriles, for which purpose semicarbazide is eminently suitable. The method has been used with particular success with derivatives of benzyl cyanide 583 the resulting phenylacetaldehyde semicarbazones were cleaved by formadehyde solution. 

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