dormouse (Member)
04-23-00 05:33
No 108765
      Red. Amin. with molecular sieves and Zn/IPA -Feck  Bookmark   

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Author  Topic:   Red. Amin. with molecular sieves and Zn/IPA 
unregistered   posted 07-28-99 06:18 PM           
Eur. J. Org. Chem 1998 1271-3.
I must admit I've never heard of this journal until now, but it sounded interesting. The basic procedure is: the ketone and amine are dissolved in IPA and dried with molecular sieves 3A for 1 hr. at room temp, and then glacial acetic acid is added and it is refluxed for 6 hrs. The heat is removed and Zn dust is added portionwise. The mixture is then filtered and the usual workup.

They used this procedure for a particular compound (BDPMA) that they could not prepare with NaBH3CN or NaBH(OAc)3 or NaBH4 (the usual reagents for red. amin.) because of a disfavored equilibrium toward imine formation. For the conversion of the carbinol amine (which is formed before the imine) to the imine, catalytic amounts of acid are needed and the optimal reaction conditions should be slightly acidic, hence the use of acetic acid. The only thing that may be different in the case of not-MDP2P and MeNH2 or whatever is that it may be better to use a much shorter reflux time, due to the relative instablity of that particular imine, and its tendency to polymerize. Anybody have any experience with this procedure or any comments, ideas?


Member   posted 09-15-99 12:03 PM          
I am very interested in Zn reductions. Was this Zn amalgam (made by adding a little HgCl2) or just the powder?
I guess that the key is the removal of water from the system. On a similar note, how about forming the ketoxime (react the P2P with NH2OH) to form a solid intermediate (ie simple to dry). Adding this to IPA, then throwing in the GAA & Zn should acheive the same result?
I assume a secondary alcohol is used to reduce ester formation?

Member   posted 09-15-99 09:18 PM          
its in the thread allready why cross post seems they have figured this out or jumming it to a start why not use the orriginal thread????????///////////////////
rev drone
Member   posted 09-16-99 12:56 AM          
I started a thread on this very subject last year, though not with reards to the article you mentioned (which is pretty nice of you, I might add. Thanks for sharing.) Just for the sake of completion, here's a link to that thread, which includes experimental procedures: Post 99260 (drone 342: "...and now a word on Zinc", Chemistry Discourse) 
-the good reverend drone

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