Reaction #1856

Reaction equation

Tetrabromomethane

triphenylphosphine

pyridine 3-carboxaldehyde

→

solid

Yield 70.0%

1,1-Dibromo-2-(3-pyridinyl)-ethylene

Yield 70.0%

Solvents

methylene chloride

Conditions

Workup

1. 1
   ExtractionThe reaction mixture was extracted with aqueous 6N hydrochloric acid (3×25 mL)
2. 2
   Extractionextracted with chloroform (4×25 mL)
3. 3
   DryingThe combined organic liquours were dried over anhydrous sodium sulfate
4. 4
   Filtrationfiltered
5. 5
   Concentrationconcentrated on a rotary evaporator
6. 6
   Otherto give a dark colored syrup
7. 7
   OtherThe crude product was chromatographed on silica gel (70-230 mesh) with chloroform:methanol (95:5) as eluant

Procedure

Tetrabromomethane (24.82 g, 0.747 mole) and triphenylphosphine (39.17 g, 0.149 mole) were stirred together in dry methylene chloride (100 mL) for 5 min. at 0° C. under a nitrogen atmosphere. To this mixture was added dropwise pyridine 3-carboxaldehyde (4 g, 0.0373 mole). The solution was then stirred for 45 min. at ambient temperature. The reaction mixture was extracted with aqueous 6N hydrochloric acid (3×25 mL), the aqueous layer basified with solid sodium bicarbonate to pH 8-9 and extracted with chloroform (4×25 mL). The combined organic liquours were dried over anhydrous sodium sulfate, filtered and concentrated on a rotary evaporator to give a dark colored syrup. The crude product was chromatographed on silica gel (70-230 mesh) with chloroform:methanol (95:5) as eluant, to afford a light yellow solid (5.0 g, 70%) which rapidly turned dark on standing.

Source