Reaction #2507825

Reaction equation

p-toluenesulfonic acid

2-(6-fluoro-3-pentylchroman-7-yl)propane-1,3-diol

6,8-difluoro-2H-chromene-3-carbaldehyde

water

→

6,8-difluoro-3-[5-(6-fluoro-3-pentylchroman-7-yl)-1,3-dioxan-2-yl]-2H-chromene

Solvents

dichloromethane

Conditions

Workup

1. 1
   Temperatureheated
2. 2
   WashThe solution is subsequently washed with sat. sodium hydrogencarbonate soln
3. 3
   Dryingand dried over sodium sulfate
4. 4
   OtherThe solvent is removed in vacuo
5. 5
   Otherthe residue is recrystallised from heptane/toluene

Procedure

1.30 g (4.39 mmol) of 2-(6-fluoro-3-pentylchroman-7-yl)propane-1,3-diol and 900 mg (4.59 mmol) of 6,8-difluoro-2H-chromene-3-carbaldehyde are dissolved in 50 ml of dichloromethane and heated under reflux on a water separator for 5 h in the presence of 50 mg of p-toluenesulfonic acid. The solution is subsequently washed with sat. sodium hydrogencarbonate soln. and dried over sodium sulfate. The solvent is removed in vacuo, and the residue is recrystallised from heptane/toluene, giving 6,8-difluoro-3-[5-(6-fluoro-3-pentylchroman-7-yl)-1,3-dioxan-2-yl]-2H-chromene (trans:cis=80:20) as a colourless solid.

Source