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温度

0 °C

A stirring suspension of 163 g (1.0 mole) of 4,5-dihydro-2-(4-hydroxyphenyl)oxazole and 276 g (2.0 mole) milled potassium carbonate in 750 ml acetonitrile was heated to reflux in a 5 liter round-bottomed flask. A total of 457.5 ml (3.0 mole) of 1,6-dibromohexane was added all at once and reflux continued for 1 hour. The reaction mixture was filtered and the cake of inorganic salts washed with 100 ml of acetonitrile. The filtrate was evaporated on a rotary evaporator (bath temperature <40° C.) and the resulting residue slurried in 1.6 liters of hexane and chilled to 0° C. The resulting white solid was filtered and washed with 500 ml cold hexane. The recovery was 263 g (80%) of white solid. A total of 535 g of crude product was slurried in 1.1 liter of refluxing tert-butyl methyl ether. The mixture was allowed to cool to 30° C. and filtered with suction. The filtrate was cooled to 0° C. and the product crystallized. The solid was filtered off and dried to yield 372 g (70% recovery) of 2-[4-(6-bromohexyloxy)phenyl]-4,5-dihydro-oxazole, m.p. 79°-81° C. The crude product can also be recrystallized from acetonitrile. This removes excess dibromohexane and most of an undesired byproduct formed by reaction of 1 mole of dibromohexane with 2 moles of 4,5-dihydro-2-(4-hydroxyphenyl)oxazole, namely 1,6-bis[4-(4,5-dihydro-2-oxazolyl)phenoxy]hexane, m.p. 174°-175° C. when isolated and purified.

1. temperaturewas heated
2. temperatureto reflux in a 5 liter round-bottomed flask
3. temperaturereflux
4. filtrationThe reaction mixture was filtered
5. washthe cake of inorganic salts washed with 100 ml of acetonitrile
6. customThe filtrate was evaporated on a rotary evaporator (bath temperature <40° C.)
7. filtrationThe resulting white solid was filtered
8. washwashed with 500 ml cold hexane
9. temperatureto cool to 30° C.
10. filtrationfiltered with suction
11. temperatureThe filtrate was cooled to 0° C.
12. customthe product crystallized
13. filtrationThe solid was filtered off
14. customdried