05-18-02 09:56
No 310393
A couple of rxn ideas to throw around. Most are completely unrelated but all are of equal importance
Swim likes sealed rxns
First.... The use of an acetone/Co2 coldfinger in the place of reflux condensor. A 2l pear shaped flask mounted through the top of rxn vessel(bucket like) it seems like it would provide a much greater cooling surface area than a standard condensor. In addition to this a tube going to a pushpull system containing slightly basic h20 to keep any MeAm in the rxn. the push pull could be acidified after the rxn and apply vaccume to the second tank to pull all the excess MeAm into the H2O as the Hcl salt. The H20/MeAm*HCl could then be reduced to approaite volume to make a working solution for future runs.
Has any one tried a push pull type containment system for reductive amination
Now with such a push pull system there is definatly going to be increced pressure/Temps during the main bulk of the rxn. How hot can the rxn be run without doing damage to the molocule. keep in mind that there is probably going to be liquid MeAm condensating from the cold finger. Will it make it back to the solvent in liquid form..
on another note.....How about forming first forming the imine with Anhydrous MeOH/MeAm with silica gel. Then filter and add activated Al dropwise similar to a borohydride reduction. Where does the H2 come from that reduces the imine? does it come from the water produced by the condensation? if so then could the Al be added all at once to anhydrous imine/MeOH and the rxn rate controled by the addition of water. How many moles of water are needed per mole of imine. Would the imine remain stable so long as the H20 was added slowly. Or would it matter? would the imine reform after the H2O present had been consumed, so long as there was a high enough concentration of MeAm?
Reflux is not nescesary for aminations is it? There would be no problem in doing it very slowly and comfortable at just above room temp.
Now some peracid Q's
All the synths swiom has seen include some kind of solvent.
The classical performic/Peracetic synths use acetone.
The modified versions use DCM as a solvent with a buffer
What happens when a performic is run without any solvent?<----(***important question***) Other than the fact that the rxn could climb to the BP of the peracid. DOes this happen without a doubt. The DCM obviously doesnot aid in the miscibility of the two phases so, is it's only purpose to control the rxn temp? Rxns that climb over 40.c have a high % of overoxidization product. Is there a minimum temp that must be met before oxidation occurs.
Does anyone have complete temp data for a 200mmole isosafrole performic with acetone? \
And alass kerplunking with MDMA. could this be adapted to be of any sort of benifit. The whole concept just seems like an A/B with heating.
VL_
