MDA with NaBH4 and am acetate review.

[cesium]

Well, from experiments SWICS done a year ago, I can conclude, that using NH3 gas alone as primary amine, requires big excess of amine to ketone, even 6.5 excess was unsatisfactory to achieve yields higher than approx. 30-33% (yes, the mixture was dried during imine formation step.....).
Without drying and/or with less NH3, or with other solvent than MeOH, yields drastically drop to 3-7%.

Recently a test run was made with Titanium isopropoxide and NH4Cl+N3Et as ammonia equivalent. Yield for this reaction was slighter better, in the range 35-40%, but, due to rather high cost of Titanium isopropoxide, this reaction will be probably limited to a small scale.

I can only emphasise that with NH3(g) drying is absolutely MUST, but with anhydrous methyl amine (g) SWICS achieved repeatedly 89 % yield even without drying (but again, with drying, you can reach even higher.......:-)

I am really interested what will be the results with ammonium acetate buffer and slow addition of ketone.

[LaBTop]

Another thing to not forget:
Ammonium acetate starts decomposing above 60°C temp, and melts at 115°C. Ammonia is lost first during the decomposition and acetic acid is formed. On raising the temperature acetamide results and water splits off:

NH₄OOCCH₃-->NH₃ + CH₃COOH
  or
NH₄OOCCH₃-->H₂NOCCH₃ + H₂O.

The acetamide distils at about 150°C. The decomposition is an endothermic process.

Thus, drying AA should be done mixed with dried silicagel, 1 : 0.5 , and under half or full vacuum, then you get sandlike, dry crystals, which should be used directly.


I did some contemplating on finetuning this difficult to master Boro One Pot, and came up with the following:

1. See above, drying of AA, if opting for a combination of AA and NH3 gas bubbling.

2. Another possibility, Ammonium carbonate, decomposition of this interesting buffering medium begins already at 20°C and reaches its maximal rate at 75°C. Ammonia, carbon dioxide and water are formed:

(NH₄)₂CO₃-->2NH₃ + CO₂ + H₂O.

It does not melt when heated as crystals, but sublimes, and in the meantime decomposes. The endothermic peak at 80°C is the enthalpy change of the decomposition. At 105°C it reaches its peak, indicating that water, remaining in the heating crucible during the decomposition, is a little overheated and evaporated quickly, the decomposition is practically finished at 100°C. By decreasing the partial pressure of the decomposition products, the decomposition can be completed at lower temperatures.
It seems that ammonium carbonate cannot be dried without decomposition.

The problem here is ofcourse, that these observations were made with pure salt, not dissolved in a solvent like methanol. But if we assume that amm. carbonate will follow at least partially these rules in solution, then it offers some interesting advantages above amm. acetate.
 
There will be 2 mols of NH₃ gas formed, and 1 mole of CO₂ gas, and 1 mole of water, for every mole of amm. carbonate decomposing, when heated to 40°C. The graph produced in above experiments indicated that 50% of the amm. carbonate will decompose at that temp when heated as standalone crystals.

And we WANT that dammed 2 moles of NH₃ gas going to help us in this reaction mixture from methanol, MDP2P, ammonium carbonate and a small amount of water, which we MUST remove as soon it is formed!

One thing I can't predict is what the carbon dioxide gas is going to do, (luckily CO2 has by far not such a tendensy to dissolve in water or methanol than NH3 gas! Most of it will bubble out of the fluid), but the water formed from amm. carbonate decomposition and the imineforming when dripping-in MDP2P, can be removed by adding lots of dried MgSO4 , combined with a lot of dried silicagel.
 
 
To force the equilibrium reaction MDP2P(in MeOH) + (NH4)2CO3 + NH3 <==> imine + NH3 + CO2 + water, to the right.

The question arises now, do we need to use excessive amounts of NH3 formed, or just a stoichometric amount, so just enough to form 100% imine?

In my opinion, we must gamble on the first option, even bubble constantly a slow stream of extra external NH3 gas in, during imine forming (so, all the time needed for dripping-in that MDP2P), and we know that imine forming for this reaction takes MUCH more time than for the other One Pots, so we keep bubbling slowly NH3 gas in the mix, even after completing dripping-in of the MDP2P.

Additional effect of this will be forcing the equilibrium to the right, all the time needed for imineforming.
My opinion is at least a period of 4 hours total, included dripping MDP2P, to give the imine forming all the time it needs to form completely.
It could turn out that that must be even much more, but only practical test can prove that feeling.

Proposed quantities for procedure nr.1 :

(I found a ref where a ketone was reduced with excess NaBH4, 10 equiv., and they found mainly the -ol, so that backs up my personal observation, that the amount of boro is quite critical, the absolute minimum to convert all imine to amine must be used, and not excessive amounts like overenthousiastic people seem to think is necessairy.)

100    MDP2P , dry, pure.
600    MeOH , dry, >98%.
300    AA , totally dry! (this acts now also as a buffer for the pH)
200    Silicagel predried in oven, does'nt dissolve, so is not in the way. You need a overhead stirrer to move all this weight around! It MUST remove all formed water! Otherwise the NH3 gas will directly be absorbed by any water!
You could throw in lots of extra MgSO4, predried, to be sure that no water is formed, MgSO4 will also not dissolve in methanol, when you filtered the powder first out with a plastic insect screen, and thus use only bigger chunks, >3mm.
X?     NH3gas bubbling till saturation point in the MeOH.
25     Boro , dry. Better first try with only 10 Boro, adding to the imine after first removing all silicagel and MgSO4. In later test you could try higher amounts, but I doubt that it will help. If your imine is converted maximal, then 10% from the started MDP2P is really enough to get max yield.
All in weight(gram) percentages.

MDA: lot of AA + NH3 One Pot:
It will work much better if you first add to the methanol at roomtemp (20 C) the pre-dried AA(if that is not fully dried, feels like dry sand then; your yield will be worthless! Dry NOT above 60C, but use vacuum and mix with half amount of dry silicagel!), under stirring, it will probably not all dissolve, no problem, it still works.
Now cool the solution to 0, but better -10 C. NH3 gas will dissolve much better in cold methanol!
Saturate at 0 to -10 C, so icecold, the full amount of methanol/AA with the dried silicagel allready in it, slowly with NH3 gas, saturation of the -10 C methanol is reached when you start smelling the NH3 above the flask.
Then you add, slowly dripping, the ketone, predried with silicagel, to the cold methanol/NH3/AA, under stirring, in a nearly closed system, when that is done, and this is the important part:

Let also NH3 gas slowly bubble in the stirred solution, to keep the NH4+ percentages near 100%, thus creating a constant NH4+ saturated solution, which will prefer imine forming instead of ammoniumsalts sidereactions.
Any NH3 escaping your flask should go through an empty washbottle first, and then a washbottle with 5% HCl/water solution, so you won't get sick from NH3 gasses.
Let it stir for at least 4 hours total (so included the ketone dripping time) at room temp (20 C) in a so good as closed system to prevent NH3 gas to escape, to give it full time to form the imine, in an NH4+ rich environment, the imine forming takes considerably more time than for the MDMA one pot. Keep bubbling NH3gas.
It will proceed from very light yellow to a distinct yellow color, that's when you have converted most P to imine.

Now start adding the boro the usual, slow way. Adding more dry silicagel or/and MgSO4 before adding the boro will remove any water formed during imine forming, remove it again before adding boro.

After completing the boro addition, proceed the usual one pot way. There you will not have any problems, it proceeds the exact same way as for MDMA or METH pots.

----------------------------------------------------------------
If a brave researcher wants to use ammonium carbonate instead of NH4acetate, use equivalent mole quantity compared to NH4acetate like in above procedure.

The rest can be done as above, only warm the reaction eventually to 40C, but you will loose quite some NH3gas, better try first roomtemp, after all MDP2P is dripped in, during dripping you work at -10 to 0 C, after completion of the adding of the MDP2P you can warm up to roomtemp or 40C for the brave ones.
----------------------------------------------------------------

MDA: lot of NH3 + AA One Pot:
Try a mix of a lot of NH3gas and AA, the AA is then acting as a buffer, I gave ratio's in the Cesium thread.
10 % AA w/w to NH3 looks good in a 10 % w/w MeOH/NH3 mix added.
So 100g MeOH + 10g NH3 + 1.1 g AA + 16.66 g MDP2P.
For every gmole of NH3 is one gmole water formed = 18 gram water !!!
To remove 18 g water you need ~~ 75 g silicagel. It takes up ~25-28 % water slowly, so adding lots of dry MgSO4 will aid water removal.

Do the best you can, there was >60% reached recently with excess of NH3gas and lots of silicagel and MgSO4 to dry the hell out of the imineforming!
LT/

PS: use 1 part MDA base + 7 parts TOLUENE to gas with HClgas, and filter, wash with acetone 1 or 2 times, ready.
WISDOMwillWIN

[DiethylEtherMan]

LT, thanx for that. Will come in real handy real soon. BTW, what pH should we be looking for during the imine formation? And if it is a bit low, would it be ok here to use GAA?

thanx.

DEM
If some of us were not so far ahead, the rest of you would not be so far behind!

[LaBTop]

In the MDMA pot you can throw the ketone in at once, the imine forms nearly directly.

We talk here about MDA, with the NH3/AA methods, and then you must create an excess of NH3gas(a lot) and some NH4+ and acetate- ions(just enough to buffer the pH) in solution, against ketone molecules, so that's why you drip the ketone in the methanolic solution, and keep slowlybubbling in NH3gas, to maintain that excess of NH3gas and NH4+, when ketone reacts with NH3 and NH4+ (this is by the way a much more complicated soup of ions than only NH3 and NH4+, UTFSE.)

The water which will not be instantly removed by the drying agents silicagel + MgSO4, will force the NH3gas to dissolve and dissociate in it, and add extra NH4+ ions to the mix, but also instignate extra OH- ions, that's why you need the acetate- (or carbonate-, or even (from NH4Cl)chloride-) ions to buffer(balance) the fast changing pH back to around 5.
And again, the MDA imine step untill maximal completion costs much more time than the MDMA imine step.

To push the product(imine) forming, you remove the side product water from the reactants solution with silicagel+ MgSO4, and keep it saturated with NH3gas.

The whole problem here is to produce enough imine, and stop it from reversing back to ketone, or proceeding further to the -ol. LT/


AN IMPORTANT THEORETICAL PS (thanks to foxy2 for digging up this formidable website ):

For those who do not exactly understand the underlaying theory, the following MUST-reads (download the MDL-Chime plugin, there's a new one out for Windows SP2 now, it works again, Netscape always worked):

http://www.cem.msu.edu/~reusch/OrgPage/VirtualText/aldket1.htm#rx1b

Nomenclature of Aldehydes and Ketones. Read all s.v.p.

Look at "Formation of Imines and Related Compounds"  exerpts:
""The reaction of aldehydes and ketones with ammonia or 1°-amines to give imine derivatives (compounds having a C=N function) plays an important role in the synthesis of amines, as discussed earlier. As for acetal formation, water is eliminated in this reaction, which is also acid-catalyzed and reversible.""

And an interesting remark, this could be a novel Hive method for identification of questionable prepared KETONES:

""With the exception of unsubstituted hydrazones, these derivatives are easily prepared and are often crystalline solids - even when the parent aldehyde or ketone is a liquid. Since melting points can be determined more quickly and precisely than boiling points, derivatives such as these are useful for comparison and identification of carbonyl compounds. If the aromatic ring of phenylhydrazine is substituted with nitro groups at the 2- & 4-positions, the resulting reagent and the hydrazone derivatives it gives are strongly colored, making them easy to identify.""
Look at: ketone + (excess) hydrazine --> hydrazone  in the top of the right block.
If we make the MDP2P and P2P and other interesting hydrazone ketone-derivatives, and they have a distinct color, then we have a perfect new ketone identification method found, the Reusch Ident, let's give the Man his well earned reward, what a fine teacher/computer-addept!

Most important remark for this thread discussion:
""The rate at which these imine-like compounds are formed is generally greatest near a pH of 5, and drops at higher and lower pH's. This agrees with a general acid catalysis in which the congugate acid of the carbonyl reactant combines with a free amino group, as shown in the above animation. At high pH there will be a vanishingly low concentration of the carbonyl conjugate acid, and at low pH most of the amine reactant will be tied up as its ammonium conjugate acid.
With the exception of imine formation itself, most of these derivatization reactions do not require active removal of water (not shown as a product in the previous equations). The reactions are reversible, but equilibrium is not established instantaneously and the products often precipitate from solution as they are formed.""
(What a pitty this doesn't work for our ketones, that would make the procedure piss-easy).
 
Now we take a look at:
""Irreversible Addition Reactions", and see there this interesting tidbit:
""Aminols (Y = NHR) are intermediates in imine formation, and also revert to their carbonyl precursors if dehydration conditions are not employed.""
""It follows then, that if nucleophilic reagents corresponding to H:(-), R:(-) or Ar:(-) add to aldehydes and ketones, the alcohol products of such additions will form irreversibly.""

And this is the description of NaBH4 reactions with ketones, sadly no reaction with imine is included, but a lot of the theory fits imine reduction also:
""Reduction by Complex Metal Hydrides"":
Exerpt:
""Addition of a hydride anion to an aldehyde or ketone would produce an alkoxide anion, which on protonation should yield the corresponding alcohol. Aldehydes would give 1°-alcohols (as shown) and ketones would give 2°-alcohols.

RCH=O   +   H:(-)      RCH2O(-)   +   H3O(+)      RCH2OH

Two practical sources of hydride-like reactivity are the complex metal hydrides lithium aluminum hydride (LiAlH4) and sodium borohydride (NaBH4). These are both white (or near white) solids, which are prepared from lithium or sodium hydrides by reaction with aluminum or boron halides and esters. Lithium aluminum hydride is by far the most reactive of the two compounds, reacting violently with water, alcohols and other acidic groups with the evolution of hydrogen gas.""

""Some examples of aldehyde and ketone reductions, using the reagents described above, are presented in the following diagram. The first three reactions illustrate that all four hydrogens of the complex metal hydrides may function as hydride anion equivalents which bond to the carbonyl carbon atom. In the LiAlH4 reduction, the resulting alkoxide salts are insoluble and need to be hydrolyzed (with care) before the alcohol product can be isolated. In the borohydride reduction the hydroxylic solvent system achieves this hydrolysis automatically. The lithium, sodium, boron and aluminum end up as soluble inorganic salts.""
And that's why flooding with water and distillation of the raw MDMA or MDA or Meth bases will take care of the problem how to get rid of the sodium borate salts left in solution.

""Modification of the Carbonyl Group.
I. Reduction:
The metal hydride reductions and organometallic additions to aldehydes and ketones, described above, both decrease the carbonyl carbon's oxidation state, and may be classified as reductions. As noted, they proceed by attack of a strong nucleophilic species at the electrophilic carbon.""

One for the hydrogenation lovers:
""Other useful reductions of carbonyl compounds, either to alcohols or to hydrocarbons, may take place by different mechanisms. For example, hydrogenation (Pt, Pd, Ni or Ru catalysts), reaction with diborane, and reduction by lithium, sodium or potassium in hydroxylic or amine solvents have all been reported to convert carbonyl compounds into alcohols.
However, the complex metal hydrides are generally preferred for such transformations because they give cleaner products in high yield.

http://www.cem.msu.edu/~reusch/OrgPage/VirtualText/special3.htm#top3

Reducing Agents, Oxidizing Reagents etc.
scroll to: Imine and Hydrazone Anions.
Exerpt:
""Still another way of circumventing some of the undesired aspects of enolate anion chemistry is to replace the oxygen of an aldehyde or ketone substrate with a 1°-amino group, in other words, to convert the carbonyl function to an imine. Imine derivatives are relatively easy to prepare, starting with an aldehyde or ketone and a 1°-amine or hydrazine derivative. The resulting C=N function does not activate alpha-C-H groups as effectively as a carbonyl function, but very strong bases such as LDA, alkyl lithiums and Grignard reagents will convert imines to their enamide conjugate bases quantitatively. This general reaction is shown in the green shaded box below."" See there for the reaction mechanism.

Another need to know fact:
""The C=N function of imines is a poor acceptor of nucleophiles,""

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =

http://www.cem.msu.edu/~reusch/OrgPage/VirtualText/amine1.htm#amin6

Nomenclature and Structure of Amines.

Click the button near the bottom: "To see an animated mechanism for imine formation". Read the whole page also. At the bottom you also can click for the "Leuckart procedure".

See also: Preparation of 1°-Amines : nr 4, change NaCNBH3 to NaBH4.
Mechanism is nearly the same as for MDA imine forming, forget the H2+Ni 2nd reaction condition:

NH3 + RCH=O -->Addition / Elimination <==>>> RCH=NH (imine) + H2O(^) --> NaBH4 Reduction --> RCH2-NH2.

Scroll down to sample 4 , forget the lightblue characters above the first arrows, look specificly at the imine forming between the big brackets !
Fill in above the last long arrow NaBH4 and cooling! and you get the picture clear in your mind.
 
An exerpt from the text below that reaction scheme:
""The method illustrated by example #4 proceeds by attack of ammonia, or equivalent nitrogen nucleophiles, at the electrophilic carbon of a carbonyl group. For present purposes it is sufficient to recognize that the C=O double bond is polarized so that the carbon atom is electrophilic. Nucleophile addition to aldehydes and ketones is often catalyzed by acids. Acid halides and anhydrides are even more electrophilic, and do not normally require catalysts to react with nucleophiles.
The reaction of ammonia with aldehydes or ketones occurs by a reversible addition-elimination pathway to give imines (compounds having a C=N function). These intermediates are not usually isolated, but are reduced as they are formed (i.e. in situ) .
Acid chlorides react with ammonia to give amides, also by an addition-elimination path, and these are reduced to amines by LiAlH4.""
Observe the removal of water (-H2O) above the imine equilibrium arrows.
Click also the box at the bottom: "Reactions of Amines Continued".

http://www.cem.msu.edu/~reusch/OrgPage/VirtualText/special3.htm#top3

Reducing Reagents.
First one we see there is NaBH4. And, under "Functions Reduced", we see not the in situ reduction of imines to amines. They still didn't catch up.
Can't blame him, it's accepted globally as impossible, proven wrong by LT/.

See also "Imine and Hydrazone Anions", exerpt:
""Still another way of circumventing some of the undesired aspects of enolate anion chemistry is to replace the oxygen of an aldehyde or ketone substrate with a 1°-amino group, in other words, to convert the carbonyl function to an imine. Imine derivatives are relatively easy to prepare, starting with an aldehyde or ketone and a 1°-amine or hydrazine derivative. The resulting C=N function does not activate alpha-C-H groups as effectively as a carbonyl function, but very strong bases such as LDA, alkyl lithiums and Grignard reagents will convert imines to their enamide conjugate bases quantitatively.""
 

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =

Another idea:
The NH3/Amm.carbonate reaction seems to be a slow kinetic reaction.
To speed up the imine forming, perhaps we could proceed after the end of the ketone dripping with adding half an amount of DCM, to keep refluxing near 40°C, and start a thermodynamically favoured reflux reaction, where the decomposing of ~50% of the (NH4)2CO3 into NH3, CO2 and water will be forced upon the reaction mechanism, thus providing still fresh finely devided NH3 gas in solution, and still be able to do this at elevated temperature(40°C). And forcing the equilibrium strongly to imine forming by removing the water with silicagel+MgSO4 and keeping the pH at 5.
2 Hours refluxing could be enough.
A closed low pressure system could do the trick better probably.
Don't forget, it's only 40°C !


Another idea: diglyme is a favourite solvent for NaBH4 reactions, why not change the whole methanol to diglyme, when starting the whole one pot, so use no MeOH at all? And keep the pH at 5 !
Rhodium, Osmium, Cesium, etc, any objections?
What's the boiling point? Am afraid it will be too high..but does not really matter, in fact. Why refluxing then, not needed then.
Does it react with any of the other reactants, reagents or products?
If not, it could be the ideal solvent for this reaction.

I really want this nagging yield problem leave behind me, it's annoying me too long, and proceed to explore the "fine tuning" of even simpler and more OTC reactions, AL/Hg/MeNH2 or Al/Hg/MeNO2 or the oxime reaction. And lots of other interesting new finds.

Let's all combine forces and get this behind us. LT/

PSII: Birch reduction theory:

http://www.cem.msu.edu/~reusch/OrgPage/VirtualText/special1.htm#birch2c

See also:

http://www.cem.msu.edu/~reusch/OrgPage/VirtualText/special1.htm#top4

Dissolving Metal Reductions of p-Electron Systems
Reduction of Isolated Carbonyl Groups
Lithium, sodium and potassium reduce ketones by a one-electron transfer that generates a radical anion known as a ketyl. Once such a reactive species is formed, it may react further by several modes, as described in the following diagram. etc.

PSIII: Leuckart reaction theory:

http://www.cem.msu.edu/~reusch/OrgPage/VirtualText/special1.htm#top4

A useful procedure for the reductive alkylation of ammonia, 1°-, & 2°-amines, in which formic acid or a derivative thereof serves as the reducing agent, is known as the Leuckart Reaction. Some examples of this reaction are shown below. etc. LT/
WISDOMwillWIN

[Semtexium]

I'm just wondering why if the NaBH4 with MeAm gas gives near quantitive yeilds, why your looking into the Al/Hg...?
            Mean People Suck             

[KrZ]

Stirrin' up some doonkie there semtex?  


Dats what IM TALKIN BOUT!!

[Semtexium]

Not at all, from day one SWIM's been improvising and trying to go as OTC as possible, and guess what, the things SWIM used for honey production are still as available as ever.  I've seen a small 1L Al/Hg(1L being the total rxn contents NOT the ketone content) get out of hand, and it's NOT pretty.  I have no doubt that Osmium has gone at the scale he mentioned but I cannot for the life of me think of ANYONE who would try an Al/Hg at 125kg scale(!?!) of ketone scale.  This NaBH4 has a nice following, and the reagents are NOT that hard to get.  I get slightly upset that the NaBH4 when first introduced here got rave(excuse the pun) reviews because there was no longer a need for mercury for honey production, which makes everything a lot better for the enviroment and such, there were even mentions of it being the way to go cause mercury is so bad for the enviroment.  But then when Osmium finally again finds his refs of long ago(thanks to polythesam I think) it shuts up the people who doubted it for so long while a bunch of hivers knew it was as Osmium stated it was all along.  Now because the fucking yeilds for it go up and are now ref'd it seems that it's now acceptable to use all that fucking mercury and in quantities I cannot even fathum to do up 125kg of fucking ketone at once!?!  Imagine how much waste material would be left over from ONE reaction at that size?!?  Oh but like most clandestine chem waste it will be disposed of properly.  All the while the very attractive NaBH4 which gives nearly quantitive yeilds already gets laid aside...  Just seems a little "off" is all...

I have to agree that hydrogenation seems the way to go at larger scales.  I don't understand write up's at such a large scale and saying that the details would only be give to a few, as I said, it seems off.  And If I was at that scale you could be DAMN sure I'd be as far away from this board as possible!!!


            Mean People Suck             

[Semtexium]

This post was originally an inside joke with another member of the hive, it was taken the wrong way by other members so I've removed it.

[LaBTop]

Semtex, if this last One Pot problem is solved, then my job to educate all these stubborn bastards here is done for that line of methods.
Why the hell should I waste more of my precious time on it then, when ALL possible details of the reactions have already been  extensively covered by me?
It does not mean that these people will directly understand it fully, but that's not my problem, but theirs, if they can't read and are too lazy to dig up easily to find theoretical background to help them understand what I'm explaining, then let them do it their way, the stupid way.
There's nothing more annoying than stupidity.

EDIT 07sept01: Sem, Excuse accepted, now it's clear. LT/

The AL/Hg/MeNO2 is the most promissing route to try to scale up, MeNH2 generation in situ, no suspicious chems to order at all.
And some remarks that it can't be scaled up wakes up the chemical engineer in me, it always can be scaled up, just invent the right reaction parameters, that's all. And that can be checked with the help of numerous researchers worldwide, I don't have to set a foot in a lab myself, I just post the procedures here, and they follow them literally, because I have proven to them to be reliable, for years already. There's nothing wrong with posting well known standards, only not well known here.
I'm not greedy, like most of you, my only task is to prevent greedy people to become too confident, or post misinformation which could do a lot of damage to people I know and respect, misinformation is our BIGGEST enemy, followed by the maniacal laws of scared to death politicians, scared by the same institutions they appointed to give reliable protection and information to the voters who put those chickenshit politicians into power at the first place.
But the protection has deformed into harassment, and the information into disinformation. LT/
WISDOMwillWIN

[KrZ]

Sulfided platinum on carbon prepared from standard Pt/C and activated with hydrazine aq. solution (silicion cell etchant) is some intensely active shit towards reductive aminations...  If you want to start crying a river about mercury pollution, why don't you talk to these guys;

http://www.mercurypolicy.org/emissions/documents/mercury_source_facts.pdf

[Osmium]

Damn, 150 tons of Hg per year in the US alone. That's quite a puddle of Hg. I bet in the past these emissions were MUCH higher, and all that Hg is of course still in the environment, since Hg doesn't simply disappear.
You guys know what? Fuckit, your quarter gram of Hg you pour down the drain after an Al/Hg is nothing compared to the amounts leaking out of broken lamps, switches, chemical factories etc. It simply doesn't matter, period.

[Semtexium]

What is the last one pot problem with the NaBH4 you refer to...?  You took what I said about the advanced vac thing the wrong way, what I'm trying to get across is why if everything is simply divided by 1000 to get grams instead of kg would you write a synth for 125kg of ketone???  Why not 125g of ketone, then tell the big boys to simply mulitply things by 1000???  I mean you said it yourself 90% of the people here are non-chemists, how many non-chemists would try it at that scale???  I think they'd prob be more likely to try it if they were given step by step instructions on how to do it at that scale.  I think giving the proceedures at a smaller scale without telling them the details of doing it at a larger scale would lead to the people who actually try it at the large scale being of the type who understand the chemistry and the risks involved.  It would certainly in my opinion bring less heat, I mean if you were some drug squad cop would you be more likely to look at things at the 125kg scale or the 125g scale?!?  I never asked nor implied that I wanted to know the secrets of which you speak, PERIOD.

And LT don't take this the wrong way, I think your ideas of the sticky threads and your VERY detailed writeups are a good idea.  The in situ generation of MeAm is very appealing and I commend all the chemists and hacks that have dramatically increased yeilds with the nitro route.

And Os, a quarter gram is in the whole picture, not that big a deal, but how much would be used in a batch that worked up 125kg of ketone...?
            Mean People Suck             

[Osmium]

About 10g I assume. Maybe 20-30. When using this much Hg it becomes possible to collect the drops of elemental Hg during workup, and the environmental impact will even be less.

When working with Al sheet the Al pretty much stops reacting when there's no imine around anymore. You will need MUCH less Al in sheet form compared to foil, and consequently much less Hg too!
The last reaction I did aminated 250g ketone with 75g Al in a 2L flask (!!!), and about half of the Al was still left when the reaction was finished. I heated it up to about 50°C once at the beginning, and then it proceeded without additional energy being added, and cooled down once the reaction was finished after 15 or so hours. To the top of the condensor a balloon was attached for smell control, and it didn't even fill up, quite to the contrary, the reaction developped a vacuum. There was NO H2 developped, NONE at all. Which means the Al is consumed quite efficiently, and nearly none is lost to side reactions. That's why I like the sheet Al/Hg so much. Clean, efficient, easy, idiot-proof and doesn't need any babysitting. Please spare me the foil nightmares, where people can barely aminate 100g of ketone in a 4L flask, and have to constantly watch the fucker so it won't boil all over the room.

[Semtexium]

SWIM's found that Al flashing is too thick for him anyways.  He was visiting a machinest's shop and saw them making Aluminum latches out of solid stock, the turnings were in between thick foil and flashing and seemed to work wonders using your method.  Foil hasn't been used for some time now since retirement so there will be no more nightmares of foil from him, rest assured...
            Mean People Suck             

[DiethylEtherMan]

Maybe I am out of wack here, but the foil method has worked wonderfully for me using 170g tone, in 12L flask and sep, 2g hgcl2, addition in 45min, and always getting more than 170g xtal back. Reaction is done in 2.5 hours (including addition)...

Yes, larger flask and sep, but I am a big boy so I can handle it. But, no MeAm needing, everything is OTC, and the thing only takes me 5-6 hours until xtal is under the lamp. Or, I can run (2) 170g reations in approx 9 hours, giving me always more than what I put in. Granted, this honey here is write from the bee themself, so it is top shelf.

Not that I am bumping anyones method, cause I am sure they are all great, but the foil isn't all that bad. The only thing that ever kept me from the sheeting is the fact that you have to make MeAm, which for some of us, is more hassle than it is worth.

anyway, this isn;t the issue is it...

still a good thread though.

peace.

DEM
If some of us were not so far ahead, the rest of you would not be so far behind!

[Osmium]

Who said you can't make MeNH2 in situ with sheet, using less solvent because the reaction will be less exothermic, and requiring no babysitting.

[Scooby_Doo]

Sunlight: Were the ketones used in these experiments made the same way? i.e. wacker or perfomic. I ask this since the only time I noted a really high yield from the cyano 70-75%, was when performic ketone was used. No matter what voodoo magic was tried the yield would never increase from a consistent 55-60% form wacker ketone.
I'm not saying this is the solution but maybe another piece to the puzzle.

[LaBTop]

I remember we discussed that topic long time ago already, and some proposals were made by me and perhaps someone else, but it was already clear that leftover copper salts or whatever from a wacker fucked up the yield of an amination.
I however do not remember clearly anymore what I or others proposed, filtering over active coal, or distillation, whatever. LT/
WISDOMwillWIN

[LaBTop]

Osmium, I'm convinced that Alu sheets must be used, who's gonna try to cool a vulcano down? And Semtex already said, since he used Alu turnings from a workshop, everything was suddenly right, it will take more time, but then you can sleep. Don't forget your promise, ehh?   LT/
WISDOMwillWIN

[Rhodium]

Shake the ketone solution with aqueous EDTA before distilling it, and absolutely no copper could be left.