Method for preparing a 4-hydroxybenzaldehyde and derivatives

Details Method for preparing a 4-hydroxybenzaldehyde and derivatives Method for preparing a 4-hydroxybenzaldehyde and derivatives

C - Chemistry, Metallurgy

07

C

C07C 45/29 (2006.01) C07C 45/38 (2006.01) C07C 45/65 (2006.01) C07C 51/255 (2006.01)

Patent

CA 2271090

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.

La présente invention a pour objet un procédé de préparation d'un 4- hydroxybenzaldéhyde et dérivés. L'invention concerne plus particulièrement la préparation du 3-méthoxy-4-hydroxybenzaldéhyde et du 3- éthoxy-4-hydroxybenzaldéhyde dénommés respectivement "vanilline" et "éthylvanilline". Le procédé de préparation d'un 4- hydroxybenzaldéhyde et dérivés est caractérisé par le fait qui consiste à oxyder sélectivement le groupe en position 2 par rapport au groupe hydroxyle, en groupe carboxylique, présent dans les composés phénoliques d'un mélange comprenant au moins: un composé phénolique (A) porteur de groupes formyle et/ou hydroxyméthyle en position 2 et 4, un composé phénolique (B) porteur d'un groupe formyle ou hydroxyméthyle en position 4, un composé phénolique (C) porteur d'un groupe formyle ou hydroxyméthyle en position 2, conduisant ainsi à un mélange comprenant un 3-carboxy-4-hydroxybenzaldéhyde, un 4-hydroxybenzaldéhyde, un acide 2-hydroxybenzoïque, qui est soumis ensuite à une opération de décarboxylation permettant ainsi d'obtenir le 4-hydroxybenzaldéhyde et un phénol qui peut être éventuellement recyclé.

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