demorol
(Hive Bee)
07-07-02 10:15
No 329629
      Methylenation of catechols
(Rated as: excellent)
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Here is a patent describing Methylenation of catechols, found on Espacenet.

Process for the methylenation of catechols Patent US3922285

Abstract
A method for the methylenation of catechols via the reaction of catechols with methylene chloride in the presence of selected strong bases is described. This process has wide applicability in the field of synthetic organic chemistry, especially in natural product syntheses.


Preparation of 1,2-methylenedioxybenzene

With bis(dimethylamino)-t-butoxymethane
3g (27 mmol) of catechol in 80mL of DCM was added dropwise over a period of 10 min to 15.5g (89 mmol) of bis(dimethylamino)-t-butoxymethane which had been prewarmed at 60 C. After the addition (1 hour) the clear mixture was refluxed at 60 C for 6 hours. The reaction material was taken up in ethyl acetate washed with 2N NaOH solution and brine. The residual liquid on removal of the solvent was distilled in a Kugelrohr at 84-86 C/16 mmHg to give 1,2-methylenedioxybenzene.

With tris(dimethylamino)methane
2.2g (20 mmol) of catechol in 75mL of DCM was added dropwise over a period of 10 min to 8.7g (60 mmol) of tris(dimethylamino)methane preheated at 55 C. Stirring and heating was continued for 17 hours, after which time the reaction mixture was diluted with 200mL DCM and washed 3 with 1N HCl, 1 with 1N NaOH and 1 with water. The liquid residue obtained on evaporation of solvent was distilled in a Kugelrohr at 85 C/15 mmHg to give 1,2-methylenedioxybenzene.


Preparation of 3,4-methylenedioxytoluene

3.1g (25 mmol) of 4-methylcatechol in 12mL of DCM was added at room temp over a period of 2 hours to 9.57g (55 mmol) bis(dimethylamino)-t-butoxymethane in 50mL of dry DCM and the mixture was kept at reflux for 6.5 hours. After standing at room temp overnight, th solvent was taken off, the residue taken up in ethyl acetate, the solution extracted 2 with 2N NaOH, washed 3 with brine and dried over anhydrous Na
2SO4. Removal of the solvent and Kugelrohr distillation of the residual brownish oil gave colorless 3,4-methylenedioxytoluene, bp 87-92 C/22 mmHg.

Unfortunately no yields are given, but I think they are not so low. The preparation of bis(dimethylamino)-t-butoxymethane and tris(dimethylamino)methane is also described in a patent, but I think posting it is not necessary. You can follow the given link and read it yourself.


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