O-Xylene → 2-Methylthioxanthone

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

2-{[2-diethylamino)ethoxy]methyl}-9H-thioxanthen-9-one (intermediate 4): 2′-diethylaminoethanol (1.17 g) was dissolved in 50 ml of absolute xylol; then during constant vigorous mixing and warming to 35-40° C. 0.24 g of solid sodium was added in small portions followed by mixing and warming of the mixture for one hour. Intermediate 3 (1.5 g) was added to the mixture in small portions, and the whole mixture was mildly refluxed for 56 hours. The solid material was removed by filtering the mixture. The organic phase was washed four times with 150 ml water. Then, the water was removed by filtration through solid water-free Na2SO4. After distillation (to remove xylol), the resulting oily, yellow-brown material was not yet pure as determined by thin layer chromatography (Kiesel gel) using benzol:ethanol:water (50:15:1.5, v/v) as solvent. The mixture was fully purified through the following steps. The mixture was first dissolved in an (CH3)2CO (acetone)/absolute ethanol (1:1, by volume) mixture followed by the addition of concentrated HCl until the solid material (HCl salt) was formed. The solid precipitate was washed with cold acetone. The HCl salt of intermediate 4 was dissolved in ethanol:water (10:90, v/v), and the solution was made basic (pH 14) by the addition of solid Na2CO3. The oily material was extracted with ethylacetate and then dried over solid Na2SO4. Intermediate 4 is 99-100% pure as determined by 1H-NMR and thin layer chromatography. The yield of intermediate 4 is ˜55%.

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