Реакция #1652

Уравнение реакции

2,5-dimethoxytetrahydrofuran

tin tetrachloride

ammonium sulfate

chlorotrimethylsilane

thymine

→

title compound

1-(5-Methoxytetrahydro-2-furyl) thymine

Растворители

dichloroethane

ethyl acetate

hexamethyldisilazane

Условия реакции

Обработка

1. 1
   ДругоеThe excess hexamethyldisilazane was removed at reduced pressure
2. 2
   workup.DISSOLUTIONthe residual oil was dissolved in xylene
3. 3
   Другоеevaporated in vacuo
4. 4
   Другоеto give a colorless viscous oil
5. 5
   ТемператураAfter cooling the solution to -30° C.
6. 6
   Температураto warm to -10° C.
7. 7
   ФильтрацияThe mixture was filtered
8. 8
   Другоеthe organic phase was separated
9. 9
   Сушкаdried (MgSO4)
10. 10
    ДругоеThe solvent was removed under reduced pressure
11. 11
    Другоеthe residual oil was chromatographed on silica gel

Методика

To a suspension of thymine (2.5 g, 20 mmol) in hexamethyldisilazane (30 mL) was added ammonium sulfate (50 mg) and chlorotrimethylsilane (0.5 mL) and the mixture was heated at 145° C. for 4 hr under nitrogen. The excess hexamethyldisilazane was removed at reduced pressure, and the residual oil was dissolved in xylene and evaporated in vacuo to give a colorless viscous oil. To this silylated thymine in dichloroethane (40 mL) was added 2,5-dimethoxytetrahydrofuran (7 mL). After cooling the solution to -30° C., tin tetrachloride (2.3 mL) was added dropwise via a syringe under nitrogen. The mixture was allowed to warm to -10° C. and was then poured into ice cold aqueous sodium bicarbonate (100 mL) and ethyl acetate (150 mL). The mixture was filtered and the organic phase was separated and dried (MgSO4). The solvent was removed under reduced pressure and the residual oil was chromatographed on silica gel using CH2Cl2 /5% MeOH as eluent to give the title compound as a cis/trans mixture in a ratio of 1:1 as shown by analytical HPLC and 1H-NMR: yield 3.4 g (75%).

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