greenyppols - 24-8-2006 at 04:13
I read protocatechualdehyde can be converted to piperonal from catechol (pyrocatechol?).
A site discusses Methylenation Of Catechols with Dichloromethane [7].
A mixture of 100ml dichloromethane and 500ml DMSO was stirred and heated to 125-130°C under a wide-bore liebig condenser. The air was displaced by
nitrogen, and then with 5-minute intervals pelleted catechol (5.5g) and pelleted sodium hydroxide (4.15g) was added simultaneously, until a total of
110g catechol and 83g of sodium hydroxide had been added during 105 minutes. After a further 20 minutes, 20ml dichloromethane and 3g sodium hydroxide
was added and the stirring was continued for yet a further 70 minutes. The reflux condenser was replaced by a Vigreux column and a constant-take-off
distillation head. Water (50 ml) was added and the benzodioxole-water azeotrope was distilled off at 98-100°, more water being added slowly as
distillation proceeded. Benzodioxole ceased to separate as a heavy oil from the distillate after ca. 600 ml. of distillate had been collected. The
aqueous distillate was extracted with ether (3x60 ml) and the combined oil and extract was dried and distilled to yield benzo-1,3-dioxole as a
colourless oil; n[D]21 1·5377, b.p. 80°/9 mm., 173-176°/760 mm.
The same procedure applied to protocatechualdehyde (13.8g) gave 9.15g piperonal (61%) after steam distillation.
An improvement of the procedure found in a patent both gives higher yield, and simpler addition of the reagents:
A solution of 110 g of catechol, 120 ml of 50% aqueous sodium hydroxide and 200 ml of DMSO was heated to 98°C and stirred at that temperature for 30
minutes. This solution at 98°C. was added over a 30 minute period to a refluxing solution of 120 ml of methylene dichloride in 300 ml of DMSO.
Thereafter, the reaction mixture was stirred at reflux for 1.5 hours. Steam was then passed into the mixture to achieve steam distillation of the
product. The distillate (600 ml) was extracted with 100 ml of methylene dichloride, which extract was washed once with 50 ml of water. The methylene
dichloride solution was then concentrated in vacuo at 40°C. to yield 119.4 g. of a colorless oil. Gas chromatographic analysis showed 97.5 percent
methylenedioxybenzene. Yield 116.4g (95.4%).
Then I located some information at another site via Reimer-Tiemann:
Protocatechualdehyde from catechol > + CHCl3 (Reimer-Tiemann) in NaOH, and conditions.
References are Tetrahedron vol 30, 2301-2305 (1974), and
Ber 36, 1031 (1903). Yields of the desired isomer is only 10-30%
From the former ref:
Dissolve 33g of catechol in 100ml of 90% aqueous methanol and 20g of
chloroform in an Erlenmeyer flask. While stirring, irradiate with three 70 watt mercury lamps for 5-10h. Remove solvent in vacuum and add 40 ml of
boiling water with stirring. Let the layers separate, cool, and filter out the crystals and wash with SMALL amounts of ice-cold water.
I read some "dodgy" poisonous compounds may be made from this if not careful.
Also, the Orgsyn site discusses protocatechualdeyde from piperonal, but Im wondering how piperonal is made not the other way around and then it and
mentions Reimer-Tiemann again, but not much info besides just mentioning it.
Is there a clearer procedure or proper direction to slap me in??
Thanks