Z_Hound (Stranger)
03-25-02 12:24
No 287733
      YAMp (Yet Another Methylation post)  Bookmark   

So.. back to reductive amination of formaline..

Did some reading, and it seems
 to me, reaction benefits greatly from weak lewis acid, ZnCl2 or, Ti(IV).

I tried to do something along the lines of Tetrah. Letters. 3, 261, 1973;
it is where they were methylating holafebrine.

 Also NaBH4 with acetic acid, using same routine as with NaCNBH3 KrZ (?) used;

 those things  are still spinning.

I have about 3g of nice crystalls of tryptamine left; and I am going to try these, eehh..
ideas:
1) do reaction in beta-mercaptoethanol, rather than in methanol. thinking that thio-acetal will form from
formaline and b-mercaptoethanol.  (5-mem ring with O and S in 1,5 positions, or something)
i have HSCH2CH2SH, but that is more expensive than bmet.; which will be, apparently, nice mild methylation agent combined with weak lewis acid and subsequent reduction.
2) try different catalysts: ZnCl2, TiCl4; and Fe(III)-AmmoniumCitrate
this is silly, but who knows: do reaction in 4A molecular seives...stirring the whole thing with mechanical stirrer.
...
Good thing, i have few gramms of methylated salt, which I can de-alkylated;
but that is saved for more desperate times.

General sentiment:
If there were good acid on the streets, who would go into that much trouble...

Z_Hound


Any Possession is a Demonic Possession!
 
 
 
 
    Rhodium
(Chief Bee)
03-25-02 23:58
No 288005
      Suggestions  Bookmark   

This is the place to start looking for experimental conditions: ../rhodium/chemistry /redamin.titanium.html

Titanium isopropoxide is a great catalyst for reductive aminations with NaBH4, and at the same time it is not acidic, and will therefore not cause any great pictet-spengler side reactions. Of course, instead of using a large excess of amine over carbonyl compound as in the examples in the text, you should instead use an excess of formalin over tryptamine, say 40 mmol of HCOH, 10 mmol tryptamine and 20-40 mmol Ti(iPrO)4.