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The preparation of AET

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starlight:
7 g (34 mmol) 1-(3-indolyl)-2-nitrobutene was added during 25 minutes to a solution of 1.6 g (42.5 mmol, 1,25 mol eq.) sodium borohydride in 17.5 ml water and 35 ml IPA.

After all the substrate was added, the solution was stirred for another 2 hours, by which time only a slight yellow color remained to the solution (starting material is pumpkin orange).

At this point 50% acetic acid was added dropwise until the effervescence subsided. NaCl was poured in until no more dissolved and stirred vigorously for five minutes. The reaction was then vacuum filtered to remove the insolubles.

The filtrate separated into an upper yellow alcoholic layer, and a lower aqeous layer. The aqeous layer was discarded. The IPA layer was added to 150ml of cold distilled water. The mixture so formed was white, opaque with no visible crystals. This mixture was extracted with 2x30ml of toluene (the toluene took on a yellow color). The toluene containing the suspected product was washed once with water and once with brine, dried with MgSO4, and then the toluene was removed at rotovap. This left ~1g of a brown oil that still smelt of toluene. This crystallized on cooling to form tan crystals in a brown liquid. The crystals were filtered off and weighed 0.3g

Most of the product was still obviously in the aqueous layer (held there by IPA/traces of toluene - should have used brine for the separation!). Another 400ml of cold distilled water was added to the still white aqueous layer and it was left overnight. In the morning, the precipitate was vacuum filtered from the now clear solution to yield a further 5.3g of cream/tan colored crystals. The filtrate was now discarded.

In total 5.6g crude 1-(3-indolyl)-2-nitrobutane were recovered which means a yield of ~78%.

The next day it was attempted to dissolve this nitrobutane in around 150ml of toluene. Most of it dissolved (not all), but the solution was a bit brown in color to indicate a pure product. Recrystallization was decided upon. unfortunately the process of rotovapping the toluene off with a bath temperature of 66C caused the toluene solution to turn a deep red color (decomposition). Petroleum ether was added to the toluene solution, and this caused about 3.5g of a brown substance to fall out of solution (the decomposed intermediate). The solution was now a yellow color.

So the moral of this story is: don't heat a toluene solution of 1-(3-indolyl)-2-nitrobutane otherwise it will decompose and ruin your intermediate.

The yellow petroleum ether/toluene solution may be usable or may not be. When the research lab reports back I will post further results.

starlight:
Well, all the carboxaldehyde / nitrobutene / nitrobutane is gone as is many, many hours of messing about.

I think it's time to call this one a day and move onto something easier for a few weeks until the appetite for the challenge has returned.

SWIM is sick of the smell of indoles!!

indole_amine:
In this paper, they reduce indolyl-nitroalkanes with nickel boride/hydrazine hydrate, rather than Pd/C.

And they prepare their intermediate nitro compound via a method similar to the one Starlight used - but deprotonate the nitroalkane beforehand, and thus get the indolylnitroalkane directly without having to reduce anything with NaBH4...



(abstract and title are mentioned here: Post 448477 (hest: "AMT in the MW oven", Tryptamine Chemistry))


indole_amine

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