Reaktion #1484065

Reaktionsgleichung

t-butylacrylate

TMS-diazomethane

TFA

→

1,1-dimethylethyl 4,5-dihydro-1H-pyrazole-5-carboxylate

Ausbeute 60.3%

Lösungsmittel

dichloromethane

toluene

tetrahydrofuran

Reaktionsbedingungen

Aufarbeitung

1. 1
   SonstigeThe solvent was evaporated under reduced pressure
2. 2
   workup.DISSOLUTIONThe crude product was dissolved in dichloromethane (70 mL)
3. 3
   Temperaturcooled in an ice bath
4. 4
   workup.ADDITIONAfter addition
5. 5
   workup.STIRRINGwas stirred at 25° C. for 0.5 h
6. 6
   SonstigeThe solvent was evaporated
7. 7
   workup.ADDITIONthe residue was neutralized by the addition of sat. NaHCO3
8. 8
   Extraktionextracted into DCM
9. 9
   TrocknenThe organic layer was dried over Na2SO4
10. 10
    Filtrationfiltered
11. 11
    Einengenconcentrated
12. 12
    Sonstigeto give the crude product which
13. 13
    Sonstigewas purified by automated silica gel column chromatography (column: 120 g, 0-38% ethyl acetate in hexane, 34 min)
14. 14
    SonstigeThe solvent was removed under reduced pressure

Vorschrift

A 1 L rb flask was charged with t-butylacrylate (11.33 mL, 78 mmol) in toluene (100 mL) and tetrahydrofuran (THF) (100 mL). To this was added via addition funnel TMS-diazomethane (50.5 mL, 101 mmol) dropwise over 25 minutes under N2. The reaction mixture was stirred at 25° C. for 4.5 h. The solvent was evaporated under reduced pressure. The crude product was dissolved in dichloromethane (70 mL) and cooled in an ice bath. To this solution was added TFA (7.21 mL, 94 mmol.) dissolved in 30 mL of dichloromethane via addition funnel. After addition was complete the mixture was stirred at 25° C. for 0.5 h. The solvent was evaporated and the residue was neutralized by the addition of sat. NaHCO3 and extracted into DCM. The organic layer was dried over Na2SO4, filtered, and concentrated to give the crude product which was purified by automated silica gel column chromatography (column: 120 g, 0-38% ethyl acetate in hexane, 34 min). The solvent was removed under reduced pressure to afford 8 g (47 mmol, 60%) of 1,1-dimethylethyl 4,5-dihydro-1H-pyrazole-5-carboxylate as pale yellow oil. LC-MS (ES) m/e 171.1 (M+H)+.

Quelle