Author Topic: Vilsmeier Success, Piperonal  (Read 1018 times)

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3547479587

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Vilsmeier Success, Piperonal
« on: April 20, 2004, 08:18:00 PM »
Into a mixture of 97.6 g (0.80 mole) of 1,2 -methylenedioxybenzene and 108 g (0.80 mole) of N-methylformanilide was introduces 135 g (0.88 mole) of phosphorus oxychloride at 50 C. over a 1 hour period. The color of the mixture was translucent orange brown . Then, the mixture was cooled to 15 C. On the other hand, 40 g of 1,2-methylenedioxybenzene was charged into another reactor and kept at 90 C. The original mixture was added to this reactor over a 5 hour period while maintaining the temperature at 90 C. When half of the mixture was added, something like a mild reflux was observed, and the mixture continued to reflux mildly until the end of the reaction. During that time, rather toxic fumes were produced. In order to contain them, a baloon was fitted on top of the addition funnel, and secured in place with some wire. After the completion of the addition, the reaction mixture was kept at 90 C. for 30 minutes, poured into ice water, and allowed to stand overnight. Then, the resulting mixture was extracted with toluene. By vacuum distillation the toluene was removed and the distillate at 84-85 C./30 mmHg was then collected to recover 56 g of unreacted benzene. Subsequently, the distillate at 131-134 C./10 mmHg was collected to obtain 67.4 g of crude piperonal. This product had a melting point of 37 C, after recrystallization from MeOH.

The aqueous phase remaining after the above described extraction with toluene was alkalified by addition of sodium hydroxide and then extracted with toluene. By vacuum distillation, the toluene was removed and the distillate at 111-113 C/50 mm Hg was then collected to recover 64.5g (0.603 mole) of N-methylaniline. Its recovery was 75.4%. No N-methylformanilide was recovered. The remaining aqueous phase was green, and clear.

Does anyone have any suggestions on Phosphorus clean up?

Does anyone have a procedure for converting the N-methylaniline to N-Methylformanilide with Formic Acid?

References: US4157333, and all over PIHKAL

Rhodium

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What phosphorus cleanup?
« Reply #1 on: April 20, 2004, 11:56:00 PM »
What phosphorus cleanup? All POCl3 has turned into sodium phosphate and sodium chloride by now... Just discard.