Author Topic: R-NH2 to R-(CH3)2NH2.  (Read 5167 times)

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R-NH2 to R-(CH3)2NH2.
« on: April 20, 2004, 03:48:00 AM »
While looking for a way to convert a bromomethylbenzene into a  phenylacetylaldahyde I ran into to this on Organic Sythesis.

Conversion of a phenethylamine to a (N,N)-dimethylphenylthylamine.

Any idea if this could be applied to tryptamine?

To 51.2 g. (1 mole) of 90% formic acid in a 500-ml. round-bottomed flask (Note 1), cooled in running tap water, is added slowly 24.2 g. (0.2 mole) of ?-phenylethylamine. To the resulting clear solution are added 45 ml. (0.6 mole) of formaldehyde solution (concentration, 37%) (Note 2) and a small boiling stone. The flask is connected to a reflux condenser and is placed in an oil bath which has been heated to 90–100°. A vigorous evolution of carbon dioxide begins after 2–3 minutes, at which time the flask is removed from the bath until the gas evolution notably subsides (15–20 minutes); then it is returned to the bath and heated at 95–100° for 8 hours.

After the solution has been cooled, 100 ml. of 4 N hydrochloric acid is added and the solution is evaporated to dryness under reduced pressure (water pump) from a water bath; the receiver is cooled in an ice bath. The pale yellow syrupy residue (or crystalline solid) is dissolved in 60–75 ml. of water, and the organic base is liberated by the addition of 50 ml. of 18 N sodium hydroxide solution. The upper (organic) phase is separated, and the lower (aqueous) phase is extracted with two 30-ml. portions of benzene. The combined organic base and benzene extracts are dried over 10 g. of anhydrous granular potassium carbonate (Note 3). After the benzene has been distilled slowly under slightly reduced pressure from a 125-ml. Claisen flask, the pressure is lowered further, and the product is distilled. The yield of colorless ?-phenylethyldimethylamine boiling at 97–98°/22 mm. (Note 4) is 22–24.7 g. (74–83%) (Note 5).


  • Guest
this won't work for tryptamines
« Reply #1 on: April 20, 2004, 11:10:00 AM »
you would end up with a beta carboline due to pictet spengler cyclization (acidic conditions promote this).