METHOD FOR SELECTIVE PREPARATION OF A 2-HYDROXYBENZOIC ACID AND A 4-HYDROXYBENZALDEHYDE AND DERIVATIVES

摘要

The invention concerns a method for the selective preparation of a 2-hydroxybenzoic acid and a 4-hydroxybenzaldehyde and derivatives, from a mixture of two phenolic compounds, one bearing a formyl or hydroxymethyl group in position 2 and the other bearing a formyl or hydroxymethyl group in position 4. The invention also concerns the preparation of a 4-hydroxybenzaldehyde from said mixture. It concerns more particularly the preparation of 3-methoxy-4-hydroxybenzaldehyde and 3-ethoxy-4-hydroxybenzaldehyde respectively called "vanillin" and ethyl vanillin". The method for preparing a 2-hydroxybenzoic acid and a 4-hydroxybenzaldehyde and their derivatives is characterised in that it consists in subjecting a mixture of phonemic compounds, one (A) bearing a formal or hydroxymethyl group in position 2, and the other (B) bearing a formyl or hydroxymethyl group in position 4, to selective oxidizing of the formyl or hydroxymethyl group in position 2 of compound (A) in carboxylic group, and optionally a hydroxymethyl group of compound (B) in position 4 in formyl group, thus resulting in a mixture of a 2-hydroxybenzoic acid and a 4-hydroxybenzaldehyde.