Reaction #1256700

Reaction equation

magnesium

epothilone A

→

epothilone C

Yield 80.0%

Solvents

THF

Conditions

Workup

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

Procedure

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