Reaktion #339859

Reaktionsgleichung

thiophene

tiglic acid

→

4,5-Dimethyl-4,5-dihydro-6H-cyclopenta[b]thiophen-6-one

Lösungsmittel

CH2Cl2

—

ice

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.ADDITIONwas added over 2.5 hours at 50° C
2. 2
   ExtraktionThe product was extracted with 3×300 ml of methyl-tert-butyl ether
3. 3
   ExtraktionThe combined extract
4. 4
   Waschenwas washed with a saturated aqueous solution of Na2CO3
5. 5
   Trocknendried over K2CO3
6. 6
   Sonstigeevaporated to dryness
7. 7
   workup.DISTILLATIONFractional distillation
8. 8
   Sonstigegave a colorless oil, bp 96-98° C./2 mm Hg
9. 9
   workup.ADDITIONa mixture of two diastereomers (ca. 3:1)

Vorschrift

To polyphosphoric acid (prepared from 500 g of P4O10 and 340 g of 85% H3PO4), a mixture of 47.6 ml (50.0 g, 0.60 mol) of thiophene and 59.5 g (0.60 mol) of tiglic acid in 80 ml of CH2Cl2 was added over 2.5 hours at 50° C. This mixture was stirred at this temperature for 2 hours, and then immersed in 1 kg of ice. The product was extracted with 3×300 ml of methyl-tert-butyl ether. The combined extract was washed with a saturated aqueous solution of Na2CO3, dried over K2CO3, and evaporated to dryness. Fractional distillation gave a colorless oil, bp 96-98° C./2 mm Hg. Yield 89.3 g (90%). On the evidence of NMR spectroscopy, the product was a mixture of two diastereomers (ca. 3:1).

Quelle