Author Topic: Zn(CN)2 formylation of 2,5-dimethoxytoluene, 79% !  (Read 646 times)

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Zn(CN)2 formylation of 2,5-dimethoxytoluene, 79% !
« on: September 30, 2003, 09:28:00 PM »
YEHAAW !! That's what I've been looking for - for nearly the last 3 years. I can barely hold back tears! Seems to be an application of the improved Gattermann synth, as described in

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4-methyl-2,5-Dimethoxybenzaldehyde (15)

2,5-dimethoxytoluene (45 g) was dissolved in dry tetrachloroethane (450 ml.). Oven dried zinc cyanide (80 g.) was added and the mixture stirred vigorously at room temperature while a continuous stream of dry hydrogen chloride was introduced. After 1 hour, the brown mixture was thoroughly cooled at 0° and 72 g. of anhydrous aluminium chloride was added. Hydrogen chloride was passed into the mixture for an additional 2 hours, maintaining the temperature at 65-70°. Additional dry zinc cyanide (40 g.) was then added, while continuing introduction of the dry gas for an additional 2 hours. Further zinc cyanide (40 g.) was added again and introduction of the gas was continued for an additional 4 hours. Sulfuric acid (550 ml, 2.5 N) was added slowly to the cooled mixture, which was then allowed to stand overnight at room temperature. The mixture was slowly heated to the boiling point and then steam distilled. The organic solvent came over first and was collected separately; this was followed by the whitish title aldehyde (42.1 g., 79% yield), which was crystallized from ethanol giving a crystalline white product, m.p. 85°;

Ref: Malesani, Giorgio; Galiano, Fabio; Ferlin, Maria Grazia; Masiero, Sergio; JHTCAD; J.Heterocycl.Chem.; EN; 17; 1980; 563-569.