#48. a-MT -by Brain

Guest · Sun May 29, 2005 10:23 am

please note that this is under construction, not yet finished, (look at the pretty colors)

TRYPTAMINE, ALPHA-METHYL; INDOLE, 3-(2-AMINOPROPYL); ALPHA-METHYLTRYPTAMINE; 3-(2-AMINOPROPYL)INDOLE; IT-290; 3-IT

SYNTHESIS : There was prepared a solution of 25.75 g indole in 100 mL DMF. A second solution was also prepared by cooling 80 mL DMF in an external ice bath (internal temperature about 12 °C), stirring well, and adding 20 mL POCl3 dropwise over the course of 30 min. This was then warmed to 25 °C and the first solution of indole in DMF was added dropwise (with continued stirring) over an additional 30 min. Stirring was continued for yet another 45 min, during which time the temperature was raised to 40 °C. Yellow solids formed during this period. The reaction mixture was poured onto chipped ice which produced a clear red solution. This was made basic with the addition of 200 mL 5 N NaOH which allowed the separation of a yellow solid. This was diluted by the addition of 200 mL hot H2O and, after cooling again, the product was removed by filtration and washed with cold H2O. This can be recrystallized from aqueous DMF to yield, after air drying, 24.5 g (84%) of indole-3-carboxaldehyde as faint orange needles.

A solution of 4.35 g indole-3-carboxaldehyde in 17.2 mL nitroethane was treated with 0.77 g ammonium acetate and heated, with occasional swirling, on the steam bath for 2.5 h. The excess reagent was removed under vacuum and the resulting yellow solids washed with H2O and air dried. Trituration under 25 mL dry MeOH, filtration, and air-drying gave 5.22 g (86%) 1-(3-indolyl)-2-nitropropene-1 as a yellow powder with mp 190-192 °C.

A suspension of 10.7 g LAH in 100 mL anhydrous THF was placed under an inert atmosphere, stirred, and treated dropwise with a solution of 10 g 1-(3-indolyl)-2-nitropropene-1 in anhydrous THF over the course of 2.5 h. The reaction mixture was brought to reflux temperature, held there for 2 h, and then returned to room temperature. The excess hydride was destroyed with an aqueous THF solution (80 mL of 25% solution) and there was then added 10 mL of 50% NaOH. There was added 150 mL Et2O, and the stirring was continued until no more solids formed. The reaction mixture was filtered and the filter cake washed with 150 mL Et2O. The filtrates and washings were combined, dried over K2CO3, and the solvent removed under vacuum. The residue weighed 9.2 g and was distilled at 130-140 °C at 1 mm/Hg to give a white oil that crystallized and had a mp of 96-98 °C. This was recrystallized from an ethyl acetate/petroleum ether mixture, and had a mp of 97-100 °C. The yield was 6.3 g (73%). IR (in cm-1): 750, 818, 911, 933, 1093, 1111. MS (in m/z): C2H6N+ 44 (100%); indolemethylene+ 130, 131 (44%, 43%); parent ion 174 (2%). A sample dissolved in 10 volumes of methanol, treated with one equivalent of glacial acetic acid, and taken to dryness under vacuum gave the acetate salt which, on recrystallization from ethyl acetate and air drying to constant weight yielded the product a-methyltryptamine (a-MT) as fine white crystals with a mp of 143-144 °C. The fumarate salt, formed by the addition of ethyl acetate to a hot solution of free base a-MT in methanol which had been neutralized with fumaric acid, was isolated as fine white needles with a mp of 200-203 °C.