Reaction #2507823

Reaction equation

hexamethylenetetramine

2,4-difluorophenol

trifluoroacetic acid

sulfuric acid

→

3,5-difluorosalicylaldehyde

Conditions

Workup

1. 1
   workup.WAITthe mixture is left
2. 2
   workup.STIRRINGto stir for 2.5 h
3. 3
   workup.STIRRINGthe mixture is stirred for a further 30 min
4. 4
   OtherThe deposited precipitate is separated off
5. 5
   Washwashed with water
6. 6
   DryingThe resultant solution is dried over sodium sulfate
7. 7
   Otherevaporated

Procedure

260 g (2.00 mol) of 2,4-difluorophenol are dissolved in 1.6 l of trifluoroacetic acid, and 560 g (4.00 mol) of hexamethylenetetramine are added in portions. After 30 min, the batch is warmed to 75° C. and stirred overnight. 2 l of 40 percent sulfuric acid are subsequently added at RT, the mixture is left to stir for 2.5 h, 1.5 l of ice-water are added, and the mixture is stirred for a further 30 min. The deposited precipitate is separated off, washed with water and taken up in dichloromethane. The resultant solution is dried over sodium sulfate and evaporated, giving 3,5-difluorosalicylaldehyde as a beige solid.

Source