i will try the hot version, as i have only really done the cool one (-20->5C). yields were ok. i did end up using alot(!) of MeNH2.HCl and i find making it hard work... (concentrating mother liquor sucks and recrystalisation is equally as time consuming...)
I will let you know comparative % yields etc. This will take approx a month as I am in the midst of sorting precursors out.
Another concern at this point in time is H20 in the MeOH.
(and yes cold verses hot gassing will make a big difference. i have seen condensation on the inside of my flask and been thinking all the time - shit - water in the reaction mixture. (so add more silica later...)
I dry the MeOH with silica gel first for a few days to soak up the existing trace water, then strain the pellets out
(I realise cooling or heating at this point is optional)
and then gas.
I add a concentrated MeNH2.HCl solution to pellets of NaOH. The gas evolved is then dried over NaOH pellets. In theory it should be anyhydrous.
Now I place silica gel into the reaction mixture to mop up H2O formed during addition of NaBH4 to maximise yield.
In the literature it says that the reaction mixture should be allowed to stir for 1-2 days or there abouts but the silica gel makes stiring of any kind difficult. The stirrer bar just gets caught up and results in generally inefficient stirring...
A solution to this would be most welcome.
I guess gram usage in the generation of 10%MeOH is what this is all about. I will quantify.
Just have to dry the damned chloroform off without introducing water... can feel a UTFSE session coming on... (or just shoving it in a flask and sticking a vacuum on it
)
Anyhow, any points of view are welcome.
Want to achieve the 90%+ efficiency mark