用DMSO 氧化（Kornblum 反应）

     将反应活性好的卤甲基化合物与 DMSO 反应，生成烷氧基锍基，然后起β-消除反应而得醛。

      本法对于活性较高的卤甲基化合物收率很好，对于活性低的卤甲基化合物，可先将其变成碘化物，然后再进行反应可得较高收率。

       对于仲卤代物经常发生消除反应，酮的收率低下。但对α-卤代酮或α-卤代酯等活性较高的仲卤代物而言，酮的收率也较高。

    A. 2-Thienylmethylhexamethylenetetrammonium chloride. In a 1-l. round-bottomed flask are placed 67 g. (0.5 mole) of 2-chloromethylthiophene, 400 ml. of chloroform, and 70 g. (0.5mole) of hexamethylenetetramine. The flask is fitted with a reflux condenser, and the mixture is boiled gently for 30 minutes. The mixture is cooled, and filtered on a Büchner funnel. Theprecipitate is washed with 100 ml. of cold chloroform, drained thoroughly, and air-dried. The yield is 128–136 g. (94–99%) of a white powder.

      B. 2-Thiophenealdehyde. The hexamethylenetetrammonium salt is placed in a 2-l. round-bottomed flask containing 400 ml. of warm water. The flask is fitted for steam distillation, and steam is passed in until all the aldehyde has distilled. The distillate is cooled, 10 ml. of 6 N acetic acid is added, and the aldehyde is extracted with two 100-ml. portions of ether. The ether solution is dried over anhydrous calcium chloride, and the ether is evaporated on a steam bath until the volume of the solution has decreased to about 50 ml. The solution is placed in a 100-ml. Claisen flask, the ether is removed by distillation, and the aldehyde distilling at 89–91°/21 mm., n 25 D 1.5880, is collected. The yield is 27–30 g. (48–53%) of acolorless oily liquid which darkens slowly on standing.