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In a 100 mL roundbottom flask equipped with a dean stark trap and a reflux condenser, 4-bromothiophene-2-carboxaldehyde (25 g, 131 mMol) and a catalytic amount of p-toluenesulfonic acid were dissolved in benzene (50 mL). The mixture was heated to reflux overnight. The reaction was cooled, washed with sat'd sodium bicarbonate, water, dried (MgSO4) and concentrated. Purification by fractional distillation (80°-90° C., 0.5 mm Hg) afforded 24.23 g (72%) of the desired dioxolane as a clear liquid.

1. customIn a 100 mL roundbottom flask equipped with a dean stark trap and a reflux condenser
2. temperatureThe mixture was heated
3. temperatureto reflux overnight
4. temperatureThe reaction was cooled
5. washwashed with sat'd sodium bicarbonate, water
6. dry with materialdried (MgSO4)
7. concentrationconcentrated
8. customPurification
9. distillationby fractional distillation (80°-90° C., 0.5 mm Hg)