反应详情

A solution of ethyl 2-aminothiophene-3-carboxylic acid (Chem.Ber.; 1965; 98; 3571-3577, 98.8 g), 4-toluenesulfonic acid (1 g) and 2,2-dimethoxypropane (158 ml) in anhydrous toluene (650 ml) was heated at reflux under nitrogen for 5 hours. The solution was allowed to cool and was then added to saturated aqueous sodium bicarbonate solution (500 ml) and extracted with ether (500 ml). The organic extracts were dried over anhydrous magnesium sulfate, filtered and evaporated. The residual oil was dissolved in ethanol (250 ml) containing sodium borohydride (8 g). The mixture was stirred for 3 days and then further sodium borohydride (8 g) was added. The mixture was stirred for 1 further day, then sodium borohydride (4 g) was added. After a further 2 days stirring, saturated aqueous sodium bicarbonate solution (750 ml) was added and the mixture was extracted with ether (2×750 ml). The organic extracts were dried over anhydrous magnesium sulfate, filtered and evaporated. The residual oil was purified by column chromatography over silica, eluting with dichloromethane/isohexane (1:1) to give the subtitle compound (24.65 g) as an oil.

1. temperatureat reflux under nitrogen for 5 hours
2. temperatureto cool
3. extractionextracted with ether (500 ml)
4. dry with materialThe organic extracts were dried over anhydrous magnesium sulfate
5. filtrationfiltered
6. customevaporated
7. dissolutionThe residual oil was dissolved in ethanol (250 ml)
8. additioncontaining sodium borohydride (8 g)
9. additionfurther sodium borohydride (8 g) was added
10. stirringThe mixture was stirred for 1 further day
11. additionsodium borohydride (4 g) was added
12. stirringAfter a further 2 days stirring
13. additionsaturated aqueous sodium bicarbonate solution (750 ml) was added
14. extractionthe mixture was extracted with ether (2×750 ml)
15. dry with materialThe organic extracts were dried over anhydrous magnesium sulfate
16. filtrationfiltered
17. customevaporated
18. customThe residual oil was purified by column chromatography over silica
19. washeluting with dichloromethane/isohexane (1:1)