Reaction #319555

Reaction equation

carbon tetrabromide

1-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)-5-ethyluracil

triphenylphosphine

sodium azide

→

1 -(5-azido-2,5-dideoxy-2-fluoro-β-D-arabinofuranosyl)-5-ethyluracil

Yield 91.6%

Solvents

dimethylformamide

methanol

Conditions

Workup

1. 1
   workup.ADDITIONwas added portionwise
2. 2
   workup.STIRRINGthe mixture was stirred for 0.5 hour
3. 3
   Otherevaporated
4. 4
   workup.STIRRINGThe residue was stirred for 0.5 hour with 8 ml of 0.5M sodium hydroxide solution
5. 5
   FiltrationThe resulting suspension was filtered
6. 6
   Washthe insoluble triphenylphosphine oxide was washed with water
7. 7
   workup.ADDITIONThe filtrate was acidified to pH 5 by the addition of hydrochloric acid
8. 8
   Extractionextracted three times with 20 ml of ethyl acetate
9. 9
   DryingThe extracts were dried over magnesium sulfate
10. 10
    Filtrationfiltered
11. 11
    Otherevaporated
12. 12
    WashThe residual solid was washed on to
13. 13
    Filtrationa filter with 10 ml of diethyl ether/petroleum ether (1:1)
14. 14
    Otherdried in vacuo

Procedure

A mixture of 0.4 g of 1-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)-5-ethyluracil, 0.44 g of triphenylphosphine, 0.48 g of sodium azide and 6 ml of dry dimethylformamide was stirred at room temperature under nitrogen while 0.48 g of carbon tetrabromide was added portionwise. The mixture was stirred at room temperature under nitrogen for 20 hours. 3 ml of methanol were added, the mixture was stirred for 0.5 hour and then evaporated. The residue was stirred for 0.5 hour with 8 ml of 0.5M sodium hydroxide solution. The resulting suspension was filtered and the insoluble triphenylphosphine oxide was washed with water. The filtrate was acidified to pH 5 by the addition of hydrochloric acid and then extracted three times with 20 ml of ethyl acetate. The extracts were dried over magnesium sulfate, filtered and evaporated. The residual solid was washed on to a filter with 10 ml of diethyl ether/petroleum ether (1:1) and then dried in vacuo to give 0.4 g of 1 -(5-azido-2,5-dideoxy-2-fluoro-β-D-arabinofuranosyl)-5-ethyluracil as a white solid of melting point 185°-188° C.

Source