反応 #62811

反応方程式

water

Br2

ethyl 2-(p-aminophenyl)propionate

potassium isothiocyanate

→

ethyl 2-amino-α-methylbenzothiazole-6-acetate

収率 48.5%

溶媒

acetic acid

acetic acid

反応条件

後処理

1. 1
   その他was also prepared
2. 2
   workup.ADDITIONwere added
3. 3
   workup.STIRRINGthe mixture was stirred for an extra half hour
4. 4
   ろ過The mixture was filtered through celite
5. 5
   抽出The product was then extracted with CH2Cl2
6. 6
   その他the organic layer was separated
7. 7
   洗浄washed with water
8. 8
   乾燥dried over MgSO4
9. 9
   ろ過finally filtered
10. 10
    その他evaporated to dryness
11. 11
    workup.DISSOLUTIONThe crude product was dissolved in 300 ml of hot ethyl acetate
12. 12
    workup.ADDITIONan equal volume of petroleum ether (40°-60° C.) was added
13. 13
    温度On cooling
14. 14
    その他cream colored crystals were formed which
15. 15
    ろ過were filtered off
16. 16
    洗浄washed with ethyl acetate/petroleum ether
17. 17
    その他dried

実験手順

The said starting material was also prepared by dissolving 154.6 g of ethyl 2-(p-aminophenyl)propionate [Arzneim. Forsch, Vol. 23, p. 1090 (1973)] in 95% acetic acid and 261 g of potassium isothiocyanate were added with stirring. A solution of 149.4 g of Br2 in 750 ml of 95% acetic acid was then added dropwise at 18°-25° C. over 2 hours and the mixture was stirred for an extra half hour, then poured into 8 liters of water. The mixture was filtered through celite and then neutralized to pH 5-6 using 6+ liters of 20% Na2CO3 solution. The product was then extracted with CH2Cl2 and the organic layer was separated, washed with water, dried over MgSO4 and finally filtered and evaporated to dryness. The crude product was dissolved in 300 ml of hot ethyl acetate and an equal volume of petroleum ether (40°-60° C.) was added. On cooling, cream colored crystals were formed which were filtered off, washed with ethyl acetate/petroleum ether and dried to obtain 97 g (48.5% yield) of the ethyl 2-amino-α-methylbenzothiazole-6-acetate melting at 146° C. A second crop of 29 g was obtained from the mother liquors for a total yield 63%.

出典