Réaction #631979

Équation de réaction

2-(3-bromo-2-methyl-phenyl)-4,4-dimethyl-4,5-dihydro-oxazole

Ethyl magnesium bromide

→

2-(3-ethyl-2-methyl-phenyl)-4,4-dimethyl-4,5-dihydro-oxazole

Solvants

ethyl ether

Conditions de réaction

Traitement

1. 1
   Autreequipped with magnetic stirring
2. 2
   Températurethermometer, and reflux condenser
3. 3
   Températurefinally at reflux for 2 hours
4. 4
   TempératureThe mixture was then cooled to 0° C.
5. 5
   Autrequenched with saturated aqueous NH4Cl
6. 6
   AutreThe organic layer was removed
7. 7
   Extractionthe aqueous layer was extracted with ether
8. 8
   Séchagedried over MgSO4
9. 9
   AutreThe solvent was removed in vacuo

Mode opératoire

2-(3-bromo-2-methyl-phenyl)-4,4-dimethyl-4,5-dihydro-oxazole (3.4 g, 12.7 mmol) was dissolved in 30 mL of ethyl ether under nitrogen atmosphere in a 100 mL round bottom flask equipped with magnetic stirring, thermometer, and reflux condenser. Ni(dppp)Cl2 (100 mg) was added and the mixture was cooled to 0° C. in an ice bath. Ethyl magnesium bromide (5.5 mL, 3M in ether) was added, the reaction mixture was stirred at 0° C. for 30 minutes, at room temperature for 2½ hours, and finally at reflux for 2 hours. The mixture was then cooled to 0° C., quenched with saturated aqueous NH4Cl. The organic layer was removed and the aqueous layer was extracted with ether. The organic phases were combined and dried over MgSO4. The solvent was removed in vacuo to give 2.84 g 2-(3-ethyl-2-methyl-phenyl)-4,4-dimethyl-4,5-dihydro-oxazole, 1H NMR (CDCl3, 200 MHz), δ (ppm): 7.5 (d, 2H), 7.2 (m, 2H), 4.1 (s, 2H), 2.7 (m, 2H), 2.45 (s, 3H), 1.4 (s, 6H), 1.2 (t, 3H), Rf=0.25 (4:1 hexane:ether), containing ca. 5% original aryl bromide. The oxazoline was suspended in 100 mL of 6N HCl and refluxed for 5 hours with vigorous stirring. The mixture was allowed to cool to room temperature, whereupon 3-ethyl-2-methyl-benzoic acid crystallized: 1.74 g, m.p. 96-98° C., 1H NMR (CDCl3, 200 MHz), δ (ppm): 7.85 (d, 1H), 7.4 (d, 1H), 7.22 (t, 1H), 2.7 (q, 2H), 2.6 (s, 3H), 1.21 (t, 3H). An additional 110 mg was recovered by ether extraction of the aqueous phase.

Source