Patent ID: 8614358

Claim:
A process for preparing 2-methyl-3-(4-tert-butylphenyl)propanal of the formula I with less than 0.3% by weight content of 2-methyl-3-(3-tert-butylphenyl)propanal of the formula II based on the total mass of the compounds of the formulae I and II starting from 4-tert-butyltoluene of the formula III with at most 5% by weight content of 3-tert-butyltoluene of the formula IV based on the total mass of the compounds of the formulae III and IV, as starting material, comprising the steps of: a) electrochemical anodic methoxylating a mixture comprising compounds of the formulae III and IV, and further comprising benzyl ethers of the formulae V and VI which are produced as intermediates to form dimethyl acetals of the formulae VII and VIII in an electrolysis solution comprising methanol, at least one conducting salt, and also optionally one cosolvent or a plurality of various cosolvents; b) hydrolyzing the mixture of the dimethyl acetals of the formulae VII and VIII formed in step a) to give corresponding benzaldehydes of the formulae IX and X and then using distillation to reduce the concentration of the benzaldehyde of the formula X; c) reacting the mixture of the benzaldehydes of the formulae IX and X obtained in step b), wherein the mixture comprises less than 0.5% by weight of the benzaldehyde of the formula X, with propanal under basic conditions to give dehydrocinnamaldehydes of the formulae XI and XII; d) catalytic hydrogenating the dehydrocinnamaldehydes of the formulae XI and XII prepared in step c) to give propanals of the formulae I and II, wherein the content of the propanal of the formula II is less than 0.3% by weight, based on the total mass of the compounds of the formulae I and II, optionally with subsequent use of distillation to remove solvent residues, precursors, and byproducts; e) optionally distilling the propanals of the formulae I and II obtained in step d), in order to reduce the concentration of the propanal of the formula II.