Hydrochloric Acid → Ethyl 2-(2,3-dihydro-1,4-dithiin-6-yl)-2-methoxyiminoacetate

Temperature

19.5 °C

A solution of ethyl 2-methoxyimino-3-oxo-4-chlorobutyrate (41.4 g.) in dried chloroform (100 ml.) was added dropwise over 1 hour at 20° C. to a mixture of ethane-1,2-dithiol (20.6 g.), triethylamine (21 g.) and dried chloroform (60 ml.). After stirring for 2.5 hours at 18 to 21° C., the mixture was adjusted to pH 1.0 with 10% hydrochloric acid. The chloroform layer was separated, washed with water (100 ml.×3), dried over magnesium sulfate and concentrated to dryness under reduced pressure at 40° C. The residue was dissolved in toluene (300 ml.), p-toluenesulfonic acid (3 g.) was added thereto and the resulting mixture was refluxed for 3 hours with removal of water. The reaction mixture was cooled to ambient temperature and an insoluble material was filtered off. The filtrate was concentrated under reduced pressure at 40° C. The residue was dissolved in ethyl acetate (300 ml.). The solution was in turn washed with a saturated aqueous solution of sodium bicarbonate (3 times) and water (twice), dried over magnesium sulfate and concentrated to dryness under reduced pressure at 40° C. to give yellow oil. The oil was subjected to column chromatography on silica gel (1 kg) and eluted with benzene. The eluate was concentrated under reduced pressure at 40° C. The residue was washed with diisopropyl ether and dried to give white crystals of ethyl 2-methoxyimino-2-(2,3-dihydro-1,4-dithiin-5-yl)acetate (syn isomer) (11 g.), mp. 65° to 67° C.

1. customThe chloroform layer was separated
2. washwashed with water (100 ml.×3)
3. dry with materialdried over magnesium sulfate
4. concentrationconcentrated to dryness under reduced pressure at 40° C
5. dissolutionThe residue was dissolved in toluene (300 ml.)
6. additionp-toluenesulfonic acid (3 g.) was added
7. temperaturethe resulting mixture was refluxed for 3 hours with removal of water
8. temperatureThe reaction mixture was cooled to ambient temperature
9. filtrationan insoluble material was filtered off
10. concentrationThe filtrate was concentrated under reduced pressure at 40° C
11. dissolutionThe residue was dissolved in ethyl acetate (300 ml.)
12. washwashed with a saturated aqueous solution of sodium bicarbonate (3 times) and water (twice),
13. dry with materialdried over magnesium sulfate
14. concentrationconcentrated to dryness under reduced pressure at 40° C.
15. customto give yellow oil
16. washeluted with benzene
17. concentrationThe eluate was concentrated under reduced pressure at 40° C
18. washThe residue was washed with diisopropyl ether
19. customdried

ORD record

ord-69fa7ffe7b994048b02e5621201b811c

Source dataset

uspto-grants-1981_09

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US04288436