活泼的芳香族化合物（如酚）与六亚甲四胺反应生成亚胺中间体，继而水解成醛。反应具有简便而迅速的特点，但这一经典方法往往产率不高，限制了它的应用。利芳香族化合物在三氟乙酸存在下与六亚甲基四胺反应，可以得到高产率的芳醛。改良方法不仅适用于活泼的芳香族化合物，亦可应用于简单的芳烃甲酰化。

Preparation of 3,5-dimethyl-4-hydroxy-benzaldehyde

     A mixture of 12.2 g of 2,6-xylenol (100 mmol), 14.0 g of HMTA (aka urotropine, hexamine or hexamethylenetetramine) (100 mmol) and 150 ml of trifluoroacetic acid was heated at reflux (83-90 o C) for 12 hrs. The products were concentrated and combined with 600 ml of ice water; the resulting mixture was stirred 15 min, made basic with Na 2 CO 3 and extracted with ether.Evaporation of the ether solution left a yellow solid which was recryst. from CHCl 3 -pentane to afford 14.3 g of 3,5-dimethyl-4-hydroxy-benzaldehyde mp 113 ℃。