GB811527A - Improvements in or relating to methods of producing aldehydes - Google Patents

Abstract

An aldehyde is produced by the reduction of benzonitrile or a nitrile of the formula R-A-CN, wherein R is an aromatic, alicyclic or heterocyclic radical and A is an aliphatic radical containing not more than 12 carbon atoms, by means of a di-alkyl aluminium hydride and hydrolysis of the aldimine complex formed in an aqueous medium. Examples of suitable nitriles are benzonitrile, cinnamic acid nitrile, b -ionylidene acetonitrile and Vitamin A acid nitrile. It is preferable to effect the reduction in an oxygen-free atmosphere, as for example in nitrogen, and at a temperature between -50 DEG and +50 DEG , using about equimolar quantities of reducing agent and nitrile. The dialkyl aluminium hydride used is preferably one in which each alkyl group contains 1 to 6 carbon atoms, for example di-ethyl or di-isobutyl aluminium hydride. The reduction may take place in an inert solvent such as n-hexane, cyclohexane, benzene, toluene, petroleum ether, diethyl ether, methyl ethyl ether, di-isopropyl ether, di-propyl ether, dioxane or tetrahydrofurane. The reaction product of the nitrile and reducing agent may be decomposed into the aldimine complex by adding moist ether and the aldimine complex may be decomposed by adding dilute acid. In examples: (1) a cooled cyclohexane solution of di-isobutyl aluminium hydride is added with stirring, in a nitrogen atmosphere, to a cyclohexane solution of b -ionylidene acetonitrile, the product is decomposed by adding dropwise diethyl ether and then water, the jelly obtained is acidified with dilute sulphuric acid and after removal of solvent the b -ionylidene acetaldehyde is distilled off in vacuo; (2) Vitamin A acid nitrile is similarly converted to Vitamin A aldehyde.