indole + SnCl4 and acetonitrile => 3-acetyl-indole: Post 451545 (https://www.thevespiary.org/talk/index.php?topic=13267.msg45154500#msg45154500)
(Chimimanie: "Thanks", Tryptamine Chemistry)
To a stirring solution of indole (1.17 g, 10 mmol) in CH2Cl2 (20 mL) under argon at 0 °C was added SnCl4 (1.44 mL, 12 mmol) was added in a single portion via syringe. After the ice bath was removed, the mixture was stirred at room temperature for 30 min, and then acetonitrile (100 mmol, 5.3 mL) was added in small portions to the suspension, followed by nitromethane (15 mL). The mixture was stirred for 4 h at room temperature. After being quenched with ice and water (30 mL), the mixture was filtered to remove inorganic precipitates, and the organic material was extracted with ethyl acetate (50 mL). The organic phase was dried over Na2SO4 and concentrated at reduced pressure to give the product as a crystalline solid.
Yield: 96%, mp: 185-191°C.
This rxn was carried out exactly as described, minus inert atmosphere, and minus the final extraction of the rxn contents being dried over Na2SO4.
During the course of the rxn the contents changed a few colors.. mainly bluish grey, to greyish blue, then grey, finally a brownish shit color.
At the end of the rxn, the contents were filtered and no visible debris was noted. This was the extracted with ethyl acetate and evaped under reduced pressure.
The flask never crystalized as expected. As the 250ml flask spun away in a 70c water bath, some darkish redish crystals were formed on areas not exposed to liqud. As the last amount of ethyl acetate left the flask time seemed to draw on and on and on. Finally it was decided that the last 1ml or so of liquid was h20 that may have carried over from the rxn's extraction. So.. fuckit, you decide to call it a night and let that last little bit evap at room temp and come back to crystals of 3-acetyl indole.
You remove the flask and see crysals forming within the liquid as the flask is cooling in your hand. You pour the contents into a 250ml beaker while it is pourable. You figure it's just h2o so let it sit in the beaker in the open air, untop of a furnace.. lightly being heated from the bottom. You come back 36h later and you have 1ml to 2ml or so of a redish/golden colored, indoly smelling liquid/oil.
SO hive dear friends, what do you think? What is the true color of acetyl indole produced this way?
The vacuum source that was used was weak, could 70c external bath temps have caused the ketone to crumble and not crystalize?
The use an inert gas was not deemed necessary due to an industrial size dehumidifier (removes moisture from air) located next to the workspace. I don't know if this could have been a factor here, or if not drying the ethyl acetate extraction is to blame. I just figured fuck the drying as the h2o couldn't possibly be that much of a pain in the ass to remove at room temp for a day. Am I wrong??
Either way, x10 scale must be attempted as we all know how addictive the smell of indole is :) Maybe at this scale things will go smoother??
Thanks!
MgSO4 might not be enough. There's a whole section in Vogel dedicated to drying and purification of solvents. Check out
http://www.chm.bris.ac.uk/safety/solvd.htm (http://www.chm.bris.ac.uk/safety/solvd.htm)
I found a source for Anhydrous Calcium Hydride at $400 per 500g, is this correct?
Yup.
It sure is expensive, do you use just a tiny bit? Is it reuseable?
You need one mole of calcium hydride for every two moles of water you want to remove, which is 1.16g CaH2 per gram water, and it is not reusable as Calcium Hydride reacts with water to give hydrogen gas - CaH2 + 2 H2O -> Ca(OH)2 + 2 H2
I was under the incorrect assumption that a drying agent such as magnesium could be used for all solvents...
Magnesium as a drying agent only works on alcohols, and never when something is dissolved in the alcohol.
So when the ethyl acetate extract is isolated, this should then be washed with a saturated solution of NaCl, then dried over Magnesium, then evaped.
Yes, except that you use magnesium sulfate and not magnesium, and that you filter off the drying agent before evaporating.
Maybe a distillation of the solvents DCM & acetonitrile would produce equal results in drying these solvents.
Definitely not.
It seems like you need to read the articles under the heading/sub-heading Equipment & Lab Technique > Solvents on the page https://www.thevespiary.org/rhodium/Rhodium/chemistry/ (https://www.thevespiary.org/rhodium/Rhodium/chemistry/)
- for example these two:
https://www.thevespiary.org/rhodium/Rhodium/chemistry/equipment/dryingchemicals.html (https://www.thevespiary.org/rhodium/Rhodium/chemistry/equipment/dryingchemicals.html)
https://www.thevespiary.org/rhodium/Rhodium/chemistry/equipment/solvent.purification.html (https://www.thevespiary.org/rhodium/Rhodium/chemistry/equipment/solvent.purification.html)