I got another idea after re-reading
Post 208935
(sunlight: "MDA with NaBH4 and am acetate review.", Methods Discourse), the whole thread.
As stated there somewhere by me, most imines are reduced in situ.
So why not add the 10-12% NaBH4 already to the Toluene/MeOH/AA mix?
Or if that doesn't work, use a Toluene/MeOH/sat.NH3gas solution, pH buffered by AA to get to pH 5.
Then the slowly dripped in ketone will form imine, and that imine will directly be reduced by the excess NaBH4 present, giving no way to the imine to proceed further to the propanol.
The ketone must be dripped in faster, because the NaBH4 will degrade slowly in the MeOH part.
Someone attended me on the fact that the MeOH:Toluene ratio should be different, because in practice it was noted that only a big amount of MeOH would totally dilute in a smaller amount of Toluene, if the other way round, 2 layers formed.
So it seems better to have the following ratio's:
I. 100 MDP2P, 600 MeOH, 200 Toluene, 300 AA, 12 NaBH4. Slow ketone dripping.
or
II. 100 MDP2P, 1200 MeOH, 400 Toluene, 400 AA, 12 NaBH4. Faster ketone dripping.
or
III. 100 MDP2P, 1000 MeOH, 333 Toluene, saturate with NH3gas, 300 AA, 12 NaBH4 (eventually add more boro, if bubbling of H2 gas decreases). Fast ketone streaming in.
There is a member who knows the data to do this reaction perfectly, so he told me, but he probably has personal reasons to keep it to himself, which I do understand, but do not totally agree with.
He claimed to had a yield of 89%, and thought that yield could be even more when the procedure will be fine-tuned.
It would be a nice gesture if he would come out of the woodwork, and help us out.
He could PM me, and I could tell him some facts why it is redundant now to keep to his principles, situations have changed to the positive for him.
I can't for some reason open my hushmails, the connection here is seemingly so slow, that I constantly get a "30 second delay caused hush to stop access to the server" message. So who knows his last mails are waiting for me, but I can't access them.
Any other members who promissed to test it out at small scale: it is obvious, that the solution to the NH3 boro one pot will open a lot of other improvements for other procedures where NH3 is involved.
So do your part of the war, get started. LT/
WISDOMwillWIN