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Author: Subject: TEMPO substitute?
DJF90
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[*] posted on 12-9-2013 at 04:27


Ah, sorry for spelling your name wrong buddy, but glad to have a reply from you what with the first hand experience and all. With the distillation, it was a simple flask-claisen head-condenser affair, which differs from your arrangement by lack of a column. However, I'm not sure a vigreux would have made all that difference, even with a variable take-off head.

What is interesting is that you mention the sample darkening. Even after a couple of hours the crystallised distillate had turned orange coloured. I wasn't sure if it was my eyes playing tricks on me or not, but I have no doubt after your comment. I suspect this material will also go to waste; the yield is terrible anyway but the important thing is that I now know how the TLC looks and so can monitor the reaction in progress for the appearance of product/impurities. Purification by salt formation doesn't appear favourable due to the presence of other basic species in there (see ninhydrin stain). Forming a crystalline derivative of the ketone might work nicely (oxime?) but its a fair bit of hassle to mess about with and potentially not end up with product. Hydrate formation might be the ticket, but theres limited data about what its soluble/insoluble in. The patent does mention it can be crystallised directly from the reaction mixture, so I may reconstitute a sample of the residue pre-distillation in acetone, add water, and see what happens.

Cheers again for your reply.
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ziqquratu
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[*] posted on 12-9-2013 at 17:36


Depending on what you plan to do with it, reacting on may be OK. Reduction of the ketone with (say) NaBH4 should be no problem, or if you planned to make the deoxygenated piperidine then making the hydrazone in preparation for the Wolff-Kishner should work well (and may give a recrystallisable product, too).
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DJF90
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[*] posted on 13-9-2013 at 05:34


I had thought of telescoping it, but given the troubles that klute appeared to have with the subsequent reactions, I figured it would be best to purify the material for the first time through. I've attached an excerpt from a book, which I found highly useful and I'd like to give this method a go (lacking ammonium nitrate and time at the moment).

The distillates have all darkened now. I can imagine this is due to having an amine (base) and ketone in the same molecule (base catalysed aldol); as the hydrate, the ketone is protected (geminal hydroxyls), and as the salt, the nitrogen is rendered inactive (protonation). It seems beneficial to isolate the triacetoneamine as one of these species, rather than as the free base. Isolation by distillation as Ziqquratu and myself have done is (probably) best followed by hydrate or salt formation.

Attachment: Triacetoneamine.pdf (603kB)
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bfesser
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