Reaktion #339857

Reaktionsgleichung

AlCl3

2,5-dimethyl-4,5-dihydrocyclopenta[b]thiophen-6-one

Br2

→

title product

Ausbeute 92.0%

3-Bromo-2,5-dimethyl-4,5-dihydro-cyclopenta[b]thiophen-6-one

Ausbeute 92.0%

Lösungsmittel

CHCl3

CHCl3

CHCl3

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.ADDITIONwas added at 0° C. over 0.5 hour
2. 2
   workup.STIRRINGThe resulting mixture was stirred for 1 hour at room temperature
3. 3
   SonstigeThe organic layer was separated
4. 4
   ExtraktionThe aqueous layer was extracted with 4×200 ml of CH2Cl2
5. 5
   WaschenThe combined organic fractions were washed with 1000 ml of saturated aqueous Na2CO3
6. 6
   Trocknendried over K2CO3
7. 7
   Sonstigeevaporated to dryness
8. 8
   workup.DISTILLATIONFractional distillation
9. 9
   Sonstigegave white crystalline product, b.p. 130° C./0.4 mm Hg

Vorschrift

To a suspension of 92.4 g (693 mmol) of AlCl3 (anhydrous powder) in 120 ml of CHCl3, 51.2 g (308 mmol) of 2,5-dimethyl-4,5-dihydrocyclopenta[b]thiophen-6-one in 50 ml of CHCl3 was added at 0° C. over 0.5 hour. The reaction mixture was stirred for 10 minutes at this temperature; then a solution of 16.6 ml of Br2 (323 mmol) in 30 ml of CHCl3 was added dropwise over 1 hour. The resulting mixture was stirred for 1 hour at room temperature, and then poured over 1000 cm3 of ice. The organic layer was separated. The aqueous layer was extracted with 4×200 ml of CH2Cl2. The combined organic fractions were washed with 1000 ml of saturated aqueous Na2CO3, dried over K2CO3, passed through a short Silica Gel 60 column (40-63 um, d 40 mm, 150 mm), and evaporated to dryness. Fractional distillation gave white crystalline product, b.p. 130° C./0.4 mm Hg. Yield 69.2 g (92%) of the title product contaminated with ca. 12% of 3-bromo-2,5-dimethyl-5,6-dihydro-cyclopenta[b]thiophen-4-one.

Quelle