反应详情

温度

130 °C

2.22 g (5.44 mmol) of the compound from Example 28A are suspended in 100 ml of triethyl orthoformate and heated to 130° C. Then, over a total period of 8 hours, 10 drops of concentrated sulfuric acid are added each hour to the reaction mixture. It is then stirred at the same temperature overnight. After cooling, excess orthoester is removed in a rotary evaporator, and the crude product is purified by column chromatography (silica gel; mobile phase: initially dichloromethane then isohexane/ethyl acetate 1:1). The product fractions are combined, the solvent is removed, and the residue is crystallized from ethyl acetate/diethyl ether. The precipitate is filtered off and dried under high vacuum. 1.80 g (77% of theory) of the title compound are obtained.

1. temperatureAfter cooling
2. customexcess orthoester is removed in a rotary evaporator
3. customthe crude product is purified by column chromatography (silica gel
4. customthe solvent is removed
5. customthe residue is crystallized from ethyl acetate/diethyl ether
6. filtrationThe precipitate is filtered off
7. customdried under high vacuum