反应详情

Sodium perborate tetrahydrate (24.5 g) was added to acetic acid (130 ml) and the mixture was heated to 50–55° C. Thereto was added dropwise a solution of ethyl 5-sulfanyl-3,6-dihydro-2H-pyran-4-carboxylate (10.0 g) in acetic acid (30 ml) over 2 h. The mixture was stirred at 50–55° C. for 3 h, and the reaction mixture was concentrated under reduced pressure. To the residue was added acetonitrile (230 ml) and the mixture was stirred at room temperature for 2 days, and the resultant insoluble material was removed off by filtration and washed with acetonitrile (70 ml). The filtrate and washing were combined and the mixture was concentrated under reduced pressure. The residue was dissolved in acetonitrile (160 ml) and the mixture was stirred at room temperature for 6 h. The obtained insoluble material was removed off by filtration, and the filtrate was concentrated under reduced pressure. To the residue was added diisopropyl ether (100 ml), and the precipitated insoluble material was filtered off to give 4-(ethoxycarbonyl)-5,6-dihydro-2H-pyran-3-sulfonic acid as a pale-yellow oil (27.6 g) containing an inorganic product.

1. temperaturethe mixture was heated to 50–55° C
2. concentrationthe reaction mixture was concentrated under reduced pressure
3. additionTo the residue was added acetonitrile (230 ml)
4. stirringthe mixture was stirred at room temperature for 2 days
5. customthe resultant insoluble material was removed off by filtration
6. washwashed with acetonitrile (70 ml)
7. washThe filtrate and washing
8. concentrationthe mixture was concentrated under reduced pressure
9. dissolutionThe residue was dissolved in acetonitrile (160 ml)
10. stirringthe mixture was stirred at room temperature for 6 h
11. customThe obtained insoluble material was removed off by filtration
12. concentrationthe filtrate was concentrated under reduced pressure
13. additionTo the residue was added diisopropyl ether (100 ml)
14. filtrationthe precipitated insoluble material was filtered off