Catalytic reduction of nitriles to aldehydes

Process for preparing compounds of the formula (I)

• 4
• where
• R1, R2, R4 and R5 are each independently hydrogen, fluorine, free or protected formyl, C1-C12-alkyl, C1-C12-alkoxy, C1-C12-haloalkyl, C1-C12-haloalkoxy, C4-C14-aryl, C5-C15-arylalkyl, —PO—[(C1-C8)-alkyl]2, —PO—[(C4-C14)-aryl]2, —PO—[(C1-C8)-alkyl)(C4-C14)-aryl)], tri(C1-C8-alkyl)siloxyl
• or radicals of the formula (II)
• A-CO-B (II)
• where, each independently,
• A is absent or is a C1-C8-alkylene radical and
• B is R6, OR6, NHR7 or N(R7)2,
• where R6 is C1-C8-alkyl, C5-C15-arylalkyl, C1-C8-haloalkyl or C4-C14-aryl and
• R7 is in each case independently C1-C8-alkyl, C5-C15-arylalkyl or C5-C14-aryl, or N(R7)2 together is a cyclic amino radical,
• or radicals of the formulae (IIIa-e)
• A—E (IIIa)A—SO2—B (IIIb)A—SO2R6 (IIIc)A—SO3W (IIId)A—COW (IIIe)
• where
• A, B and R6 are as defined above and
• W is OH or NH2, and
• R3 is hydrogen, fluorine, chlorine or bromine,
• comprising reacting compounds of the formula (IV)
• 5
• where
• R1, R2, R3, R4 and R5 are as defined under formula (I)
• with hydrogen, in the presence of water and in the presence of acid or acidic salts, the acids or acidic salts having a pKA value of from 1 to 6 based on an aqueous basis system at 25° C. and in the presence of a nickel- and aluminium-containing catalyst.