| 摘要 |
The invention concerns a method for preparing a 4-hydroxybenzaldehyde and derivatives. More particularly it concerns the preparation of 3-methoxy-4-hydroxybenzaldehyde and of 3-ethoxy-4-hydroxybenzaldehyde called "vanillin" and "ethylvanillin" respectively. The method for preparing a 4-hydroxybenzaldehyde and derivatives is characterised in that it consists in selectively oxidising the group in position 2 relative to the hydroxyl group, in carboxylic group, present in the phenolic compounds of a mixture containing at least: a phenolic compound (A) bearing formyl and/or hydroxymethyl groups in position 2 and 4; a phenolic compound (B) bearing a formyl or hydroxymethyl group in position 4; a phenolic compound (C) bearing a formyl or hydroxymethyl group in position 2; thus leading to a mixture containing a 3-carboxy-4-hydroxybenzaldehyde, a 4-hydroxybenzaldehyde, a 2-hydroxybenzoic acid, which is then subjected to a decarboxylation for obtaining the 4-hydroxybenzaldehyde and a phenol which can be optionally recycled. |
