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Easy NaBH4 amination

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XrLeap:
SWIM received a PM on doing the NaBH4 amination easy way.

The method has been mentioned all over bee hive, but there is no detailed description on it. SWIM is now posting this in NewBee forum for sharing. Please bear with it if this has been described in detail before.

This is the LabTop's methanol method with easy generation of methylamine gas.

Materials:

MDP2P 1 weight unit
Methylamine.HCl 0.7 weight unit
NaOH 0.42 weight unit
Methanol 3 weight unit
NaBH4 0.1 weight unit

3A molecular sieves 0.5 unit

1) Dissolved all methylamine.hcl in warm methanol.
2) Dissolved all NaOH in the previous solution, while applying cooling with ice/salt bath.
3) Filtered the NaCl formed after methylamine gas generation in situ completed. One can see that all NaOH has been dissolved.
4) Throw in some amount of 3A mol sieves to hopefully dry the methanol. Stir for 1 hour. 24 hours would be good.
5) Added the PMK cooled.
6) Added NaBH4 a la LabTop.
7) Removed cooling, stirred for 21 hours.

Workup as usual. The standard workup for SWIM:
1) Throw in 3x or 4x volume of 10% NaOH into the solution. PH as high as possible.
2) Let settle, meaning there are 2 layers formed.
3) Seperate the lower layer in this case.
4) Add in DCM(low boiling point, good extraction) to extract more freebase, 3 times would be enough. Now the aqeous solution should look very clear.
5) Make the soluion acidic, pH 3 is good, by adding dilute acid solution.
6) Discard the DCM layer now. This contains maybe unreacted PMK.
7) Make the aqeous solution alkaline.
8) Extract with DCM 3 times.
9) Distill off DCM, residual Methanol or other lower boiling stuff. Under atm pressure, stirring is applied for distilling very volatile solvent like DCM.
10) Apply vacuum to distill the lovely smell free base.
11) To squeeze over the last drops, turn off the vaccum, bring the flask's temperature higher by 15C to 20C. Then apply the vaccum again. Red or grey tar forms in the flask.

This is nothing new, but SWIM just wishes to share what he received from fellow helpful bees.

XrLeap:
Oops, SWIM forgot to indicate yield. 85% m/m can be achieved repeatedly. MDP2P used was obtained thru benzo wacker, 1 time distilled.

1 way to improve further is to add the 3A mol sieves after PMK addition, to remove H2O from imine formation.

XrLeap:
SWIM is using this method to aminate his ketone: Post 531792 (XrLeap: "Easy NaBH4 amination", Newbee Forum)

In the cooling part, SWIM tried to use dry ice to cool the methanol solution and it became below -20C. This was during addition of NaBH4, the temaperature stayed below 0c until all NaBH4 was added. Lowest was way below what a normal thermometer could indicate.

However, there was problem. When SWIM returned the next day, there was still a lot of NaBH4 undissolved(teampurature @ 21C), the methanol solution(methanol, methylamine, ketone, NaBH4) looked very concentrated. SWIM went on to work up(A/B extraction plus distill) and obtained only about 50% yeild.

Is adding of NaBH4 needed to be between 0 to 150C? SWIM started from below -20C. This was done on multi mol scale.

Could imine formation be done under -20C?

Could amine formation be done under -20C?

Or could it be that methylamine.HCL and NaOH could not react to produce methylamine(free base) + NaCL + H20 under -20C?

If it was possible to produce methylamine(free base) + NaCL + H20, will the H20 become solid(ice) under that temperature?

Allow SWIM to say thank you for taking your precious time in reading this. Thank you.

XrLeap

LaBTop:
Making 10% MeAm-gaseous/MeOH, Imine-forming, and Amination !
In the cooling part, SWIM tried to use dry ice to cool the methanol solution and it became below -20C. This was during addition of NaBH4 (LT: that's the Imine to Amine forming step!), the temperature stayed below 0°C until all NaBH4 was added. Lowest was way below what a normal thermometer could indicate.
--- End quote ---

The first procedure you are confusing is to use Methanol as cold as can be, to obtain a 10% MeAm-gaseous/Methanol solution by introducing gaseous Methylamine from a gas cylinder or any other means in very cold Methanol.
You have to repeatably re-cool the Methanol, since adding of MeAm gas will quickly warm up the Methanol, thus you have to put your vessel back in a freezer a few times.
OR, instead of a freezer, you use a cooling vessel around your mixing vessel where you dropped chunks of dry-ice in f.ex. Acetone (stinks) or Methanol(you already have it at hand, and it doesn't stink), to force-cool your fast warming up MeAm/Methanol mixture during bubbling MeAm gas.
However, there was problem. When SWIM returned the next day, there was still a lot of NaBH4 undissolved(temperature @ 21°C), the methanol solution(methanol, methylamine, ketone, NaBH4) looked very concentrated. SWIM went on to work up(A/B extraction plus distill) and obtained only about 50% yeild.
--- End quote ---

That is caused by a much too low temperature of the NaBH4 addition step. What you were seeing when returning was a lot of decomposed NaBH4.
The NaBH4 addition step must be performed at temps between 0 and 5°C, so, cooling with simple COLD water from the tap with lots of icecubes in it, is sufficient to keep the temperature in that range.
Logical ofcourse, since you add only relatively very small portions (1:100) of NaBH4 to a huge motherliquid load of Methanol, and that big mass will never warm up as quickly as the other first step, the preparation of a 10% gaseous MeAm/Methanol solution (1:10).
1. Is adding of NaBH4 needed to be between 0 to 15°C? SWIM started from below -20°C. This was done on multi mol scale.
2. Could imine formation be done under -20°C?
3. Could amine formation be done under -20°C?
4. Or could it be that methylamine.HCL and NaOH could not react to produce methylamine(free base) + NaCL + H20 under -20°C?
5. If it was possible to produce methylamine(free base) + NaCL + H20, will the H20 become solid(ice) under that temperature?
--- End quote ---

1. That's the Editimine to amineEndEdit formation step! Between 0 and 5°C. Stay away from roomtemperature and freezing temps of the WHOLE stirred motherliquid, the cooling liquid however can and will have a MUCH lower temperature as the motherliquid, because it can only cool the walls of the motherliquid-vessel!!! That's why cooling liquid temperature indications of a 1000 liter vessel are VERY very different from a 2 liter vessel! The motherliquid load to be cooled is much smaller in the latter case, so you probably read my huge One-pot method and didn't realize that those are instructions for huge scale procedures. I expected those times, my readers to understand that Chemical Engineering is quite different from a research lab with a RotoVap with a 2 liter reaction flask.
So, always stirr fast and powerfull in big vessels and in small glass vessels in relation to the flask. And read the temperature of the MOTHERLIQUID, and only compare that to the reading of the COOLING LIQUID. Thus keeping a fine balance between extraction of energy from the motherliquid via the walls of your vessels, by your cooling liquid.
And do not throw chunks of dry ice INTO the motherliquid. Do you know the effect of CO2 on your reaction? No.
2. That's too cold. See 1.
3. EditNot advisable. See again 1., keep it between 0 and 5°C.EndEdit
When supposing you mean gassing of the amine-base fluid with HCl gas, again, don't overdo, cool the Acetone or Toluene in a freezer, that's the easiest way, and then bubble HCl gas in, and replace the vessel in the freezer when you can feel with your hands on the vessel wall that the temperature rose too high. This repeatingly cooling of the crystalizing process will in the end reward you with the highest yield of crystals.
4. You proved to yourself already that it greatly delays the process, so, you only needed someone else to tell you: Yes, not sufficiently.
5. If enough NaCl salt will be present and will form a saturated solution in the formed water, plus a portion of non soluted salt, you have to look up a freezing table of saturated salt solutions. But in your case, it is mixed with a freebase gas MeAmine, which will make that table useless. Only practice will tell you fast. But you can freeze a lot of solutions, when you go cold enough. But I do understand what you ask, can I separate the water and the salt, by freezing, from the freebase MeAm.
Or do you ask if you can salt out freebase Methylamine gas, out of the formed salty water? Then you must add the Methanol in your little list and the NaOH.
Practice will show you.  :)

Edit: I think now, that basically, you ask in point 5, perhaps this:
If adding extra salt from an extern source (a pot of NaCl) to the motherliquid of Methanol, MeAm.HCl, NaOH beads, AFTER the NaCl + H2O formed , aiming to end up at a thoroughly saturated salt solution of the WATER, formed as a reaction product of the .HCl from the Methylamine.HCl salt with the NaOH (which also forms the water as a second reaction product), will salt out the Methyl amine GAS freebase, out of the formed water, so it stays SOLELY soluted in the Methanol. But Methanol mixes indefinitely with water, your first problem.
Your second problem, you indicated that all NaOH soluted, and that you filtered off the rest of the non-soluted NaCl, which means, that your water part was already saturated, otherwise you would have not seen any solid NaCl.
You better do the stochiometric calculations, to find out for yourself, how much, in grams, water will be formed with the amounts in grams you took for the reaction participants.
You will see that there is not that much water formed, and that it is saturated with NaCl salt, making it more difficult for Methanol to mix with that water.
Let's look at your first steps:
1) Dissolved all methylamine.hcl salt in warm methanol.
2) Dissolved all NaOH in the previous solution, while applying cooling with ice/salt bath.
3) Filtered the NaCl formed after methylamine gas generation in situ completed. One can see that all NaOH has been dissolved.
4) Throw in some amount of 3A mol sieves to hopefully dry the methanol. Stir for 1 hour. 24 hours would be good.
--- End quote ---

Freezing the water out instead of step 3 to safe time, will be complicated or not possible, practice will proof it, because you have a Methanol/saltwater mixture, which mixtures are notorious for lowering their freezing points, compared to the sole constituents of the mixture.
So, try freezing the water out after step 3, but without filtering the precipitated NaCl salt. Because if you succeed, you only have to separate the ice and the NaCl from the MeAm/Methanol mix.

I still think using dried silicagel beads from Merck will do the trick, sucking up the water, in one to two hours under strong mixing in a closed vessel, so no new water from the air can be added.
And I also assume that perhaps Bariums wet boro method will avoid a lot of these problems.
However, if you feel comfortable with this method, after finetuning it with the temps I gave you, this will be just as easy, since you indicated that before you used that far too strong cooling during imine forming (with CO2 dry-ice chunks, perhaps even thrown in the motherliquid, which is wrong), everything worked out fine, with a 80 to 85% yield molar/molar.
I hope you meant that by giving yield in m/m.
EndEdit.

You really all need to read this thread first, before attempting testruns:
Post 439864 (Vibrating_Lights: "Imine reduction", Newbee Forum) .
And then try first to understand all implications of what is posted there.
An example of more extensive knowledge, obtainable from that thread is from this post:
Post 440189 (LaBTop: "Excellent Boro info I page 1", Newbee Forum) :
Sodium borohydride reductions are generally conducted in solvents such as methanol or ethanol due to its high solubility in them. However, the efficiency of sodium borohydride in these solvents is very poor due to the high rate of decomposition. Conducting the reaction in two phases using non-polar aprotic solvents such as hydrocarbons and a phase transfer catalyst can alleviate this problem. In hydrocarbon solvents sodium borohydride is stable and does not undergo decomposition reaction and thus its complete utilization can be realized.
--- End quote ---

Because of that high rate of decomposition, we add very small portions of NaBH4 to very big amounts of 10%MeAm/Methanol, at such a highest possible temperature (ca.+5°C), that the inevitable decomposition has the smallest chance to occure!
And look for posts of Barium for his use of hydrocarbons and a phase transfer catalyst( PTC ) like Alliquat, in his wet methods.
LT/

LaBTop:
has changed that strange 4.16 % to 41.6 %, that seemed also a bit strange to me, when I read and reread that text.
( Post 440349 (Aurelius: "JACS 74(9), 2346-2348 (1952)", Newbee Forum) , the sup-text in blue halfway.)
In the same text, something interesting caught my attention while reading it, but I never saw anyone commenting on it:
Aqueous Metathesis with Lithium Borohydride.

Although lithium borohydride ordinarily reacts violently with water, it was discovered that if the pure compound is introduced anaerobically at or below 0*C, a solution results with but minor loss of activity.  Air-free distilled water is employed.  The resulting solution is sufficiently stable to permit its use over a period of hours.
--- End quote ---

This could be an important yield promotor in Bariums wet boro method.
Why should sodium borohydride not act the same.
 
Can anybody, preferably Barium and those familiar with the latests methods, try the latest wet method imine forming procedure out under high vacuum? LT/

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