Reaktion #345760

Reaktionsgleichung

2-phenyl-4-(β-hydroxyethyl)thiazole

ethyl propionylacetate

p-toluene-sulfonic acid hydrate

→

ethyl 6,7-dihydro-4-ethyl-2-phenyl-4H-pyrano[4,3-d]thiazole-4- acetate

Lösungsmittel

toluene

Reaktionsbedingungen

Aufarbeitung

1. 1
   Temperaturis heated
2. 2
   Temperaturat reflux temperature
3. 3
   Sonstigewith water separation
4. 4
   workup.ADDITIONAdditional ethyl propionylacetate (6 g) and p-toluenesulfonic acid hydrate is added
5. 5
   Temperaturrefluxing
6. 6
   workup.WAITis continued for 24 hr
7. 7
   SonstigeThe mixture is evaporated under reduced pressure
8. 8
   Sonstigethe residue is triturated with petroleum ether
9. 9
   workup.DISSOLUTIONThe residue is dissolved in a mixture of aqueous sodium bicarbonate solution and ether
10. 10
    SonstigeThe organic solution is separated
11. 11
    Trocknendried over sodium sulfate
12. 12
    Sonstigeevaporated under reduced pressure

Vorschrift

A mixture of the starting material of formula II, 2-phenyl-4-(β-hydroxyethyl)thiazole (30.8 g, 0.15 mole, described in Example 1), ethyl propionylacetate (28.8 g, 0.2 mole) and p-toluene-sulfonic acid hydrate (0.25 mole) in toluene (1200 ml) is heated at reflux temperature, with water separation, for 17 hr. Additional ethyl propionylacetate (6 g) and p-toluenesulfonic acid hydrate is added and refluxing is continued for 24 hr. The mixture is evaporated under reduced pressure and the residue is triturated with petroleum ether. The residue is dissolved in a mixture of aqueous sodium bicarbonate solution and ether. The organic solution is separated, dried over sodium sulfate and evaporated under reduced pressure to give ethyl 6,7-dihydro-4-ethyl-2-phenyl-4H-pyrano[4,3-d]thiazole-4- acetate (IV, R1 = H, R2 = CH2CH3, A= COOCH2CH3 and n= 1).

Quelle