Method for producing bisbenzoxazoles
A technology of benzoxazole and phenoxy, which is applied in the field of preparing bisbenzoxazole, and can solve problems such as undesired effects
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Embodiment 1
[0061] Embodiment 1: 1, the preparation of 4-bis-(benzoxazol-2'-yl)-naphthalene
[0062] Suspend 3.55 g (16.4 mmol) of naphthalene-1,4-dicarboxylic acid and 4.05 g (37.1 mmol) of o-aminophenol in 12.1 g of 1,2,3,4-tetralin and stir under argon Heat for 20 minutes to 180°C. The ammonium salt-containing suspension thus obtained was admixed with 0.35 g of boric acid and 0.1 g of p-toluenesulfonic acid and exposed to microwave irradiation at 300 W for 2 hours in a vessel with KPG-stirrer and water trap. A temperature of about 230° C. measured by means of an IR sensor was reached. This temperature is kept constant by evaporative cooling. The reaction mixture was then cooled to room temperature within 10 minutes, where the product crystallized out in the form of yellow needles.
[0063] HPLC of the reaction batch mixture showed complete conversion of naphthalene-1,4-dicarboxylic acid to 1,4-bis-(2"-benzoxazolyl)-naphthalene. After filtration, the crystals were washed with methano...
Embodiment 2
[0063] HPLC of the reaction batch mixture showed complete conversion of naphthalene-1,4-dicarboxylic acid to 1,4-bis-(2"-benzoxazolyl)-naphthalene. After filtration, the crystals were washed with methanol and dried Afterwards, 1,4-bis-(benzoxazol-2'-yl)-naphthalene with a purity of more than 99.5% was obtained. Embodiment 2: Preparation of 1,4-bis-(benzoxazole- 2'-yl)-naphthalene
[0064] 0.71 g (3.3 mmol) of naphthalene-1,4-dicarboxylic acid and 0.81 g (7.4 mmol) of o-aminophenol were suspended in 2.4 g of N-methylpyrrolidone with stirring in a pressure-resistant glass test cell. After addition of 169 μl of tetrabutoxytitanium, the ammonium-salt-containing suspension thus prepared was exposed to microwave radiation at 300 W for 15 minutes in a pressure-resistant, closed test chamber with stirring and external cooling. A temperature of about 225[deg.] C., measured by means of an IR sensor, is reached, with the pressure rising to approximately 20 bar. The reaction mixture was...
Embodiment 3
[0066] Example 3: Preparation of 1,2-bis-(5-methylbenzoxazol-2'-yl)-ethene
[0067] 2.3 g of fumaric acid and 5.52 g of o-amino-p-cresol were homogenized in 12.45 g of tetralin with heating and stirring. The ammonium salt-containing suspension thus prepared was admixed with 42 mg boric acid and 12 mg p-toluenesulfonic acid and exposed to microwave irradiation at 300 W for 30 minutes with stirring in an open apparatus with complete external cooling. A temperature of about 220° C. measured by means of an IR sensor was reached. The reaction mixture was then cooled to room temperature within 10 minutes. The yield of 1,2-bis-(5-methylbenzoxazol-2'-yl)-ethylene was 65% based on fumaric acid.
[0068] After filtering off, washing the crystals with methanol, extracting the remaining acid by stirring with alcoholic sodium hydroxide solution and drying, 1,2-bis-(5-methylbenzoxazole-2' with a purity of more than 98% is obtained -yl)-ethylene.
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