Water → 1,4-Dihydro-2,6-diphenyl-4-oxo-1(2,2,6,6-tetramethyl-4-piperidinyl)-3-pyridinecarboxylic acid
Reaktionsgleichung
[C:1]1([CH3:7])[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1.[O:8]1[CH:13]=[CH:12][CH:11]=[CH:10][C:9]1=[O:14].[NH2:15][CH:16]1[CH2:21][C:20]([CH3:23])([CH3:22])[NH:19][C:18]([CH3:25])([CH3:24])[CH2:17]1.[OH2:26]>>[C:1]1([C:7]2[N:15]([CH:16]3[CH2:17][C:18]([CH3:25])([CH3:24])[NH:19][C:20]([CH3:23])([CH3:22])[CH2:21]3)[C:13]([C:1]3[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=3)=[CH:12][C:11](=[O:26])[C:10]=2[C:9]([OH:8])=[O:14])[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1Komponenten
5
Versuchsvorschrift
A 250 ml round-bottom flask is equipped with a mechanical stirrer, thermometer, and a distillation head and condenser set up to remove distillate. The flask is charged with 100 g (0.52 moles) ethyl benzoylacetate and 0.075 g sodium bicarbonate. The flask and its contents are heated by means of an oil bath over a period of about 5 hours at temperature from ambient to a maximum of 200° C. while the ethanol formed is continuously removed. Unreacted ethyl benzoylacetate is removed by vaccum distillation. The residue consisting of crude 3-benzoyl-6-phenyl-2H-pyran-2,4-(3H)-dione is then heated at 80°-85° C. with 500 g of 85% sulfuric acid for 4 hours. This mixture is poured into 1 liter of ice-water and the water extracted three times with 150 ml portions of chloroform. The combined chloroform extracts are stripped of volatiles on a rotary evaporator and the residue of 2,6-diphenyl-4-oxopyran-3-carboxylic acid isolated by fractional crystallization. A toluene solution of this pyrone is then treated with an equal molar quantity of 4-amino-2,2,6,6-tetramethylpiperidine and refluxed with removal of water by means of a Dean-Stark trap. When water has ceased to separate, the toluene is removed on a rotary evaporator and the residue cooled and treated with hexane to promote crystallization of the crude product. The product is further purified by fractional crystallization.