活潑的芳香族化合物（如酚）與六亞甲四胺反應(yīng)生成亞胺中間體，繼而水解成醛。反應(yīng)具有簡便而迅速的特點，但這一經(jīng)典方法往往產(chǎn)率不高，限制了它的應(yīng)用。利芳香族化合物在三氟乙酸存在下與六亞甲基四胺反應(yīng)，可以得到高產(chǎn)率的芳醛。改良方法不僅適用于活潑的芳香族化合物，亦可應(yīng)用于簡單的芳烴甲?；?/p>
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 ℃。
