3153-97-7Relevant articles and documents
Method for preparing a 4-hydroxybenzaldehyde and derivatives
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, (2008/06/13)
The present invention concerns a process for the preparation of a 4-hydroxybenzaldehyde and its derivatives. More particularly, the invention concerns the preparation of 3-methoxy-4-hydroxybenzaldehyde and 3-ethoxy-4-hydroxybenzaldehyde, respectively known as vanillin and ethylvanillin. The process for the preparation of a 4-hydroxybenzaldehyde and its derivatives is characterized in that it consists of selectively oxidising, to a carboxy group, the group in the 2 position with respect to the hydroxyl group, present in the phenolic compounds in a mixture comprising at least a phenolic compound (A) carrying formyl and/or hydroxymethyl groups in the 2 and 4 position, a phenolic compound (B) carrying a formyl or hydroxymethyl group in the 4 position, a phenolic compound (C) carrying a formyl or hydroxymethyl group in the 2 position, resulting in a mixture comprising a 3-carboxy-4-hydroxybenzaldehyde, a 4-hydroxybenzaldehyde and a 2-hydroxybenzoic acid, which then undergoes a decarboxylation operation to produce the 4-hydroxybenzaldehyde and a phenol which can optionally be recycled.
ON THE REGIOSELECTIVITY OF THE FREMY'S SALT OXIDATION OF PHENOLS
Deya, Pedro M.,Dopico, Mercedes,Raso, Angel Garcia,Morey, Jeronimo,Saa, Jose M.
, p. 3523 - 3532 (2007/10/02)
A detailed study of the regioselectivity of the Fremy's salt oxidation of phenols, including a series of MNDO calculations of the intermediate phenoxy radicals, has been carried out.The analysis of these results has led us to establish a new rule for the para vs. ortho regioselectivity, namely: "C-4 unsubstituted phenols, as well as phenols substituted at C-4 with easy-to-displace groups, undergo oxidation (or oxidative degradation) by the action of Fremy's salt, thus eventually providing the corresponding p-quinones".A similar rule for the ortho vs. ortho' regioselectivity could not be so precisely formulated since now steric effects play a significant major role.