Reaction #2507832

Reaction equation

hydrochloric acid

potassium tert-butoxide

(6-fluoro-3-pentylchroman-7-ylmethyl)triphenylphosphonium bromide

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

→

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

Solvents

water

THF

THF

Conditions

Workup

1. 1
   workup.WAITthe batch is left
2. 2
   Extractionextracted three times with MTB ether
3. 3
   Washphases are washed with sat. sodium chloride soln
4. 4
   Dryingand dried over sodium sulfate
5. 5
   OtherThe solvent is removed in vacuo
6. 6
   Otherthe residue is chromatographed on silica gel with heptane/toluene (1:1)
7. 7
   Otherrecrystallised from heptane at −20° C.

Procedure

10.2 g (17.7 mmol) of (6-fluoro-3-pentylchroman-7-ylmethyl)triphenylphosphonium bromide are dissolved in 50 ml of THF, and 2.0 g (17.8 mmol) of potassium tert-butoxide are added with ice cooling. After 1 h, a solution of 6,8-difluoro-2H-chromene-3-carbaldehyde in 50 ml of THF is slowly added dropwise, and the batch is left to stir overnight at room temp. The solution is subsequently added to water, acidified using dil. hydrochloric acid and extracted three times with MTB ether. The combined org. phases are washed with sat. sodium chloride soln. and dried over sodium sulfate. The solvent is removed in vacuo, and the residue is chromatographed on silica gel with heptane/toluene (1:1) and recrystallised from heptane at −20° C., giving 6,8-difluoro-3-[2-(6-fluoro-3-pentylchroman-7-yl)vinyl]-2H-chromene as yellow crystals.

Source