The Duff reaction or hexamine aromatic formylation is a formylation reaction used in organic chemistry for the synthesis of benzaldehydes with hexamine as the formyl carbon source. The method is generally inefficient. The reaction is named after James Cooper Duff.
The reaction requires strongly electron donating substituents on the aromatic ring such as in a phenol. Formylation occurs ortho to the electron donating substituent preferentially, unless the ortho positions are blocked, in which case the formylation occurs at the para position.[1]
The modified salicylaldehyde 3,5-di-tert-butylsalicylaldehyde is prepared by the Duff reaction: