clearly_not_atara - 14-3-2020 at 11:30
With acetic acid, the Duff reaction works only on phenols and anilines. But with trifluoroacetic acid, the reaction scope is much broader, and even
toluene can be formylated.
What I wonder is if other acids could work? The first thing that comes to mind is oxalic acid, which has acidity closer to trifluoroacetic acid but
still reacts like a carboxylic acid in many situations. Pyroglutamic acid, lactic acid or pyruvic acid might also be effective. Sulfonic acids were
not so good IIRC. In this paper a mixture of acetic and trifluoroacetic acids was used for the formylation of 1,4-diethoxybenzene and
4-(4'-phenoxyphenoxy)-benzene:
https://www.arkat-usa.org/get-file/19827/
Attachment: smith1972.pdf (241kB)
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[Edited on 14-3-2020 by clearly_not_atara]