SciWiz - 1-10-2013 at 15:38
I am an undergrad student presently and was reading this weekend about piperidones. This is a theoretical discussion only of course. But I was
wondering about a synth I found which has also been mentioned elsewhere on this board. I'm interested in the N-alkylation part of these reactions. I
have ZERO interest in the final product. My interest was sparked because of how different the two methods are at performing specifically the
N-alkylation, after doing several searches it seems to me that the methods of N-alkylation are highly contested, in fact, one member even speculated
that the pt-br method Seigfried was posted to distract would be cooks. So, with the 2 methods below, I'm wondering if they are even legitimate.
Here are the two synthesis:
http://www.scribd.com/doc/30448083/A-Convenient-One-Pot-Synt...
http://www.google.com/patents/EP2252149A2?cl=en
First of all if you look at the second synthesis:
In two neck round bottom flask equipped with condenser 17.6 gms (0.10 moles) of 4-anilinopiperidine obtained from step 1, and 50 ml of 100% sodium
hydroxide was added. The reaction mixture was heated up to 6O0C and 27.75 gins (0.15 moles) of 2-phenethyl bromide was then added. The reaction
mixture was stirred for 5 hrs. After the completion of the reaction, the reaction mixture was poured in the ice cooled water. The crude product was
obtained by filtration and recrystallised from petroleum ether (60 to 8O0C) to give colourless crystals of 4-aniHno-N-phenethyl piperidone
Where is the phase transfer catalyst in this reaction? How is this possible?
In the other synthesis:
To a stirred suspension of 4-piperidone monohydrochloride (15.36 g,0.1 mol) in dichloroethane (450 ml), triethylamine (27.87 ml, 0.2 mol)and
phenylacetaldehyde (11.17 ml, 0.1 mol) were added and stirred for half an hour at room temperature under N2
. Thereafter sodiumtriacetoxyborohydride (30 g, 0.14 mol) was added to the reactionmixture with continuous stirring. Reaction mixture was further
stirredfor 24 h. Aniline (9.12 ml, 0.1 mol), acetic acid (11.53 ml, 0.2 mol)and sodium triacetoxyborohydride (30 g, 0.14 mol) were then added and
again stirred for 24 h.
In this one the 4-piperidone is reductively alkylated with STAB and phenylacetaldehyde in the presence of a base, triethylamine. Is dichloroethane
necessary? or could one use DCM for example, or DMSO. Couldn't one use K2CO3 instead of triethylamine?
zed - 8-10-2013 at 18:12
Many of us don't have the permits required, and thus don't have first hand experience with such materials. If you ever decide to execute such a
synthesis, you'd better have all your paperwork in order. Free-lancing such a project, could result in a thirty year vacation.
Use the search engine.
http://www.sciencemadness.org/talk/viewthread.php?tid=23242#...
http://www.dtic.mil/dtic/tr/fulltext/u2/a250611.pdf
[Edited on 9-10-2013 by zed]
[Edited on 9-10-2013 by zed]
chemrox - 16-8-2015 at 17:17
Apparently both methods are dry labs. Be suspicious of journals that aren't peer reviewed and this also applies to Chinese authors publishing in acs;
natural products