反应详情

4-Nitrophenylacetic acid (6.7 g, 37 mmol) and then dicyclohexylcarbodiimide (8.0 g, 39 mmol) were added, at room temperature, to a dichloromethane (100 ml) suspension of 6-methyl-dihydro-2,4-pyrandione (4.73 g, 36.9 mmol) which was synthesized by the hydrogenation of 4-hydroxy-6-methyl-2-pyrone, after which 4-dimethylaminopyridine (0.23 g, 1.9 mmol) was added and stirring carried out for 1 hour and then further 4-dimethylaminopyridine (0.46 g, 3.8 mmol) added and stirring carried out for 23 hours at room temperature. The dicyclohexylurea was filtered off while the solution was still warm, then the reaction solution washed with dilute hydrochloric acid (50 ml), after which the aqueous layer was extracted with dichloromethane. After drying with anhydrous sodium sulphate, the solvent was distilled off and separation and purification performed by column chromatography. When recrystallization was performed from ethanol, 4-hydroxy-6-methyl-3-(4-nitrophenylacetyl)-5,6-dihydro-2-pyrone (5.9 g, 55%) was obtained as yellow crystals. Tetrahydrofuran (100 ml), methanol (35 ml) and concentrated hydrochloric acid (10 ml) were added to the compound (2.00 g, 6.9 mmol) obtained, then Pd-C (5%, containing 100% of water, 300 mg) added and the atmosphere replaced by hydrogen. The raw material was consumed in 4 hours and then the hydrogen replaced by argon. The precipitate was filtered off, washed with hot methanol, and the filtrate concentrated. When the solid obtained was recrystallized from ethanol, 3-(4-aminophenylacetyl)-4-hydroxy-6-methyl-5,6-dihydro-2-pyrone hydrochloride (1.43 g, 70%) was obtained. A chloroform (15 ml) solution of the compound obtained (500 mg, 1.68 mmol) was ice-cooled and 2-thiopheneacetyl chloride (0.25 ml, 2.1 mmol) added. Next, pyridine (0.41 ml, 5.4 mmol) was added and stirring carried out for 3 hours. After returning to room temperature, stirring was carried out for 15 hours, then dilute hydrochloric acid added and extraction performed with dichloromethane. The organic layer was dried with anhydrous sodium sulphate, and the solvent distilled off. When recrystallization was performed from ethanol, Compound 6 (317 mg, 49%) was obtained as pale yellow crystals.

1. stirringstirring
2. waitcarried out for 23 hours at room temperature
3. filtrationThe dicyclohexylurea was filtered off while the solution
4. temperaturewas still warm
5. washthe reaction solution washed with dilute hydrochloric acid (50 ml)
6. extractionafter which the aqueous layer was extracted with dichloromethane
7. dry with materialAfter drying with anhydrous sodium sulphate
8. distillationthe solvent was distilled off
9. customseparation and purification
10. customWhen recrystallization