Réaction #1256700

Équation de réaction

magnesium

epothilone A

→

epothilone C

Rendement 80.0%

Solvants

THF

Conditions de réaction

Traitement

1. 1
   workup.ADDITIONTo a two-necked flask was added
2. 2
   AutreThe flask was flame-dried under vacuum
3. 3
   Températurecooled under argon
4. 4
   AutreThe stirring suspension was evacuated with low vacuum
5. 5
   workup.ADDITIONthe reaction flask was refilled with argon
6. 6
   Autrehomogeneous deep green after 1.5 h
7. 7
   Autrebeing consumed
8. 8
   AutreAn aliquot (3.5 mL, 0.70 mmol, 3.5 eq) was removed
9. 9
   TempératureThe reaction mixture was warmed to room temperature
10. 10
    AutreThe volatiles were removed in vacuo
11. 11
    Autrethe residue was chromatographed two times on silica (25 g)
12. 12
    Lavageeluting with 35% EtOAc/hexanes

Mode opératoire

To a two-necked flask was added chopped pieces of magnesium turnings (24 mg, 1.0 mmol). The flask was flame-dried under vacuum and cooled under argon. Bis (cyclopentadienyl)titanium dichloride (250 mg, 1.0 mmol) was added followed by anhydrous THF (5 mL). The stirring suspension was evacuated with low vacuum, and the reaction flask was refilled with argon. The red suspension became dark, turning a homogeneous deep green after 1.5 h with nearly all the magnesium metal being consumed. An aliquot (3.5 mL, 0.70 mmol, 3.5 eq) was removed and cooled to −78° C. under argon. To this solution was added epothilone A (99 mg, 0.20 mmol, 1.0 eq). The reaction mixture was warmed to room temperature and stirred for 15 min. The volatiles were removed in vacuo and the residue was chromatographed two times on silica (25 g), eluting with 35% EtOAc/hexanes to give 76 mg (80%) of epothilone C as a pale yellow viscous oil.

Source