LAH lithium aluminum

Dialky Itryptaminesfrom Tryptamines. Helv. Chem. Acta, 49,1199 (1966). Heat 82 ml of acetic anhydride with 35 ml of formic acid for 2 hours at 60°. With stirring add dropwise a solution of 100 g of tryptamine in 250 ml of THF. After the addition, cool to room temp (slowly) and let stand for 12 hours. Evaporate the solvents off in vacuo and add water (cold) to precipitate oily formyl tryptamine, which is separated and recrystallized in the minimum amount of aqueous (50%) ethanol (the minimum amount will be under 750 ml). 35 g of the recrystallized formyltryptamine is added to 150 ml of THF and mixed gently and then added to 20 g of LAH (lithium aluminum hydride) in 400 ml of THF. After this addition (which is made dropwise) reflux for 12 hours. Cool to 15° and add 10 ml of water (when decomposing LAH with water or alcohol always add it slowly, dropwise and be careful), then 10 ml of 15% NaOH, and about 30 ml more water or until the bubbling has stopped. Filter, wash the precipitate off with a little THF and evaporate (the filtrate) in vacuo to get the dialkyltryptamine (about 20 g). Recrystallize the residue in about 100 ml of dry methanol and reprecipitate by adding 10 g of anhydrous oxalic acid. 

Scheme 1. Abbreviations TFAA, trifluoroacetic anhydride DMF, N,N-dimethylformamide 2EHCOC1, 2-ethylhexanoyl chloride LAH, lithium aluminum hydride MeOTf, methyl trifluoromethanesulfonate.

HMPA hexamethylphosphoric triamide LAH lithium aluminum hydride... 

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