METHOD OF SYNTHESIS OF 4-HYDROXYBENZALDEHYDE AND ITS DERIVATIVES Russian patent published in 2002 - IPC

FIELD: organic chemistry, chemical technology. SUBSTANCE: invention relates to novel method of synthesis of 4-hydroxybenzaldehyde and its derivatives, in part, to method of synthesis of 3-methoxy-4-hydroxybenzaldehyde (vanillin) and 3-ethoxy-4-hydroxybenzaldehyde (ethylvanillin). Method involves the selective oxidation of group at position 2 with respect to hydroxyl group to carboxyl group in mixture of phenolic compounds said oxidation reaction is carried out in the presence of base and catalyst based on palladium and/or platinum. Said mixture of phenolic compounds comprises at least: phenolic compound (A) as a carrier of formyl and/or hydroxymethyl groups at position 2 and 4 and corresponding to the formula (IIA) ; phenolic compound (B) as a carrier of formyl or hydroxymethyl group at position 4 and corresponding to the formula (IIB) ; phenolic compound (C) as a carrier of formyl or hydroxymethyl group at position 2 and corresponding to the formula (IIC) being in indicated formulas (IIA)-(IIB)-(IIC): Y₁ and Y₂ are similar or different and they mean one of the following groups: group CHO; group -CH₂OH; Z₁,Z₂Z₃ are similar or different and they mean hydrogen atom, (C₁-C₄)-alkyl, (C₁-C₄)-alkenyl or (C₁-C₄)-alkoxy-group being said groups are linear or branched ones, phenyl, hydroxyl group, halogen atom that results eventually to preparing mixture containing 3-carboxy-4-hydroxybenzaldehyde, 4-hydroxy- -benzaldehyde, 2-hydroxybenzoic acid being the latter is subjected for decarboxylation that ensures to obtain 4-hydroxybenzaldehyde and phenol that can be recirculated if necessary. Invention provides the economically effective method of synthesis, high productivity in minimal amounts of by-side substances formed. EFFECT: improved method of synthesis. 38 cl, 2 ex