(Hive Bee)
07-04-02 15:05
No 328680
(Rated as: excellent)
Freifelder stated a long time ago that phenylacetone + aq.methylamine -> N-methylimine which is hydrogenated to N-methylamphetamine. The wet enviroment doesn´t disturb the imine formation. Yet when bees here want to make MDMA they tend to choose anhydrous conditions. In particular in the borohydride reduction of the imine to amine.
I decided to challenge this:
10g 2-fluorophenylacetone (65mmol) was dissolved in 50ml toluene and to this was added a solution made of 10.6g (130mmol) ethylamine HCL and 5.25g NaOH in 50ml water. The mixture was vigorously stirred at room temp for 2 hours. The aqueous phase was then removed and the toluene phase was transferred to a 250ml rb flask containing 1.9g NaBH4 (50mmol), 25ml water and 15ml EtOH and the mixture was vigorously stirred for a further 2 hours at room temp. Diluted hydrochloric acid was then added dropwise until pH2 was reached, the phases was separated and the toluene phase was extracted twice with 20ml 5% HCL and then discarded. The combined aqueous phases was made strongly alkaline with 50% aq NaOH and extracted twice with 50ml toluene. The toluene extracts was dried over MgSO4 and stripped of solvent in a rotovap. The residual yellow oil (nasty smell) was dissolved in 50ml EtOAc and dry HCL in IPA added until pH4 was reached. The white crystals was isolated and dried to constant weight.
Yield 8.9g (40.9mmol,62.9%) N-ethyl-1-(2-fluorophenyl)-2-aminopropan
Longer reaction times and 4-5 eq ethylamine should give better yields.
So many things to do, so little time....
(Chief Bee)
07-04-02 16:02
No 328699
I think it has been mentioned earlier by Sunlight that the reaction does not need to be strictly anhydrous when methylamine is used (40% straight from the bottle), but the yield is a little on the low side like yours - around 60%. It is very important to use anhydrous conditions if ammonia is used as the amine though, the unsubstituted imine is just too unstable in an aqueous environment.
Strange substrates you choose - but I assume that you are an intelligent guy who wants to work for our cause by developing methods for us to use without ever having to own a controlled substance, putting yourself at risk, correct?
Entropy just isn't what it used to be.
(Hive Bee)
07-04-02 16:47
No 328712
Yeah, I´m just developing methods. Which kind of substituted substrates anyone then wants to use is a matter of choice to every bee.
By doing it this way I can work really open ordering everything I need through the major companies without questions.
(Hive Bee)
07-04-02 20:53
No 328773
say for example someone wanted to reductivly aminate Phenylacetylcarbinol to PPA, and used ammonium acetate as opposed to ammonia? Or conversly methylamine (acetic salt)
Would this improve the stability of the shiff's base and inhibit imine polymerization?
Another modifer would be to dry the shiff's base substrate with drying agent prior to reduction, will the shiff's base prepared from ammonim acetate reduce under the aluminum amalgum reduction scheme?
Sorry about all the dumb questions.
(Chief Bee)
07-05-02 05:09
No 328895
Al/Hg is a very low yielding method for producing primary amines from ketones, not recommended.
I don't see how using ammonium acetate instead of ammonia in the amination would help imine formation, only drying agents like molecular sieves (or other) is really effective here, and even then the yields aren't stellar.
However, ammonium formate and Pd/C will probably make PPA in good yield from l-PAC, see the new paper at ../rhodium/pdf /redamin.cth-p
Entropy just isn't what it used to be.
(Hive Bee)
07-05-02 06:10
No 328910
Thanks that's good article.
It's interesting to note that they speak of this hemiaminal intermediate pathwat as some "new" discovery.
There are pretty old papers detailing this very same intermediate in reductive amination reactions.
Maybe they speak of this specific substrate?
(Hive Bee)
07-05-02 09:27
No 328967
(Rated as: excellent)
I decided to try a number of variations of the previous reaction. Since I have not yet learned to use all the functions of this place properly I cannot upload any documents. So I have to write this one.
Rxn A B C D E
1 Et 1 0.5 1 52%
2 Et 2 0.5 1 55%
3 Et 1 1 1 56%
4 Et 2 1 3 73%
5 Me 1 0.5 1 55%
6 Me 2 0.5 1 56%
7 Me 1 1 1 49%
8 Me 2 1 3 78%
A. RNH2 R=
B. Time for imine formation in hours
C. Eq. NaBH4 to substrate
D. Imine reduction time
E. Yield of amine HCl
The substrate was 2-fluorophenylacetone in all reactions.
The volumes of solvents were the same as in the original reaction in this thread, as were the work up.
It seems that the critical part is the imine reduction time.
(Chief Bee)
07-05-02 13:13
No 329012
What? You ran 25 reactions yesterday? How many mmol each, and how did you analyze them? HPLC and then something with graph area calculation?
The methylamine aminations, where they performed exactly the same way using MeNH2.HCl?
Entropy just isn't what it used to be.
(Hive Bee)
07-05-02 14:50
No 329024
it was just 11 reactions altogether. 9 reductive alkylations and two other reductions.
I used 65mol 2-fluorophenylacetone for each reaction. I have not done a HPLC on them yet. The yield is just from the first crystallisation. I´ll recrystallise them later and run a HPLC on all of them.
(Hive Bee)
07-05-02 17:23
No 329050
Got P2P?
you used 65 MOL?/rxn? mmol, maybe?
(Hive Bee)
07-05-02 23:39
No 329140
I have always assumed based on what I've been told about NaBH4 that the reason for using anhydrous conditions with the NaBH4 reductive amination is that if you don't use anhydrous conditions then the extra H2O molecules will destroy the free hydride ions supplied by the NaBH4 before those hydride ions ever have a chance to reduce the respective imine to its corresponding amine, and yields will suffer.
LaBTop was the one responsible for popularizing this method here as I recall, and he stressed using anhydrous conditions to get the 99% yield that he claimed, so maybe he will have something to add to this thread.
(Hive Bee)
07-06-02 01:54
No 329163
To an alcohol, acidic or basic aqueous solutions will speed degradation of the hydride.
NaBH4 is a strong reducing. agent, that's why NaBHCN is used instead. If the substrate is anhydrous then equilibrium is to the right on Imine/hemiaminal RXN and the ketone isn't around to be reduced.
(Old P2P Cook)
07-06-02 05:19
No 329218
C. Eq. NaBH4 to substrate
I am guessing that you really are specifying the molar ratio not an equivalence ratio.
If you would use more than 1 mole of NaBH4 per mole of P2Pmethylimine you could get 80-85% yield and could reduce the amount of time allowed for imine formation and reduction.
(Hive Bee)
07-06-02 09:44
No 329274
Aurelius: Of course it was mmol. Sorry but I was kind of tired when I wrote that.
neuromodulator: acid aqueous solutions destroy borohydrides really quick. But slightly alkaline aqueous solutions are quite stable. Some companies actually sell aqueous alkaline sodium borohydride solutions in huge quantities.
Spisshak: cyanoborohydride won´t touch the ketone at all at a specific pH, that´s the very reason for using it. It´s called selectivity.
Terbium: Yes molar ratio. Sorry again..
What I really wanted to see with those variations were when the yield would go up. Not having to use 5 mol amine/mol ketone or 4 mol borohydride/mol imine. With 2 mol amine/mol ketone and 1 mol borohydride/mol ketone it was the imine reduction time that was critical.
(Hive Bee)
07-06-02 17:07
No 329319
Barium: Yes, that makes perfect sense in that NaBH4 dissociates into an equilibrium mixture of Na+, BH3, BH4-, and H- so alkalinity will of course not destroy the hydride ions in that case.
However, to get the absolute maximum yield in the reductive amination of a ketone the pH must be exactly 7.0 based on the studies I dug up years ago. As long as the NaBH4 is only slightly alkaline, I don't guess it is going to make any kind of a significant difference, though, which is your point I guess.
(PVC-Analog Taste-Tester)
05-18-03 07:07
No 433839
If the yields are that good with a wet borohydride reductive alkylation, I imagine it would work-out great with NaBH(OAc)3!
Love my country, fear my government.
(Hive Addict)
06-10-03 15:06
No 439050
Unfortunately triacetoxyborohydrides are very sensitive to water. So wet conditions can't be used with them. But under dry conditions they are great selective reducing agents.
Freaky
(Chief Bee)
06-10-03 15:33
No 439059
I cannot seem to find a decent preparation of sodium triacetoxyborohydride, where it is made sure that the product doesn't contain any excess HOAc - could anybody help me find such a prep? Commercial sodium triacetoxyborohydride is a little too steep...
(Hive Addict)
06-10-03 16:56
No 439071
(Rated as: excellent)
I use this method to make my own sodium triacetoxyborohydride:
To a suspension of 100 mmol sodium borohydride in 50 ml dry toluene is added 300 mmol GAA dropwise during good stirring. The temperature is kept below 30°C with cooling. When the gas evolution ceases, about 20 minutes, the suspended sodium triacetoxyborohydride is isolated by filtration1 and washed once with freshly distilled EtOAc. The filtercake is dried to constant weight under vaccum. The yield is almost quantitative if dry ingredients are used.
1. If one is accurate in measuring out the reagent (no excess HOAc) the toluene suspension can be freed from toluene by distillation under reduced pressure (bp. about 40°C @ 80 mbar). The result is a good quality sodium triacetoxyborohydride.
Commercial manufacturers use THF instead of toluene but I don't see any reason why since the product is as good if toluene is chosen.
Freaky
(Hive Addict)
06-16-03 14:48
No 440288
(Rated as: excellent)
It seems like there is no great benefit from anhydrous conditions anymore, unless one wants to squeeze out the highest possible yield.
1-(2,4-dimethoxyphenyl)-2-propanone, 250 mmol
Methylamine HCl, 375 mmol
NaOH, 375 mmol
Sodium borohydride, 290 mmol
Aliquat 336, 5 mol%
Toluene
Water
To a solution of the ketone in 100 ml toluene was added a solution of 25,3 g methylamine hydrochloride in 30 ml water followed by dropwise addition of 15 g NaOH dissolved in 40 ml water while stirring the mixture violently. The addition of NaOH was allowed to take five minutes so the liberated methylamine had time to react with the ketone instead of being pushed out of solution. When the addition was complete the mixture was stirred for another hour at room temperature. The aqueous layer was then separated and discharged.
To the toluene solution of the imine was added 4,8 g (12 mmol, roughly 5 mol%) Aliquat 336 followed by a solution of 11 g sodium borohydride in 35 ml water containing 25 mg NaOH1 in one portion. The mixture was violently stirred2 for one hour at 35° by slight warming. The residual borohydride was destroyed by addition of diluted acetic acid until gas evolution ceased and the aqeous layer separated and discharged. The toluene solution was extracted with 3x100 ml 10% HCl and the extracts combined, washed with 50 ml toluene and saturated with NaCl.
The aqueous solution was then made alkaline with NaOH until pH 14 was reached and extracted with 2x50 ml toluene. The combined toluene extractions was washed once with water and once with brine, and then dried over MgSO4. The solvent was removed at 40° @ 80 mbar leaving a slightly yellow oil weighing 48 g (92%). The hydrochloride was made by dissolving the free base in 250 ml EtOAc and adding 5N HCl/IPA until pH 4 was reached. Sparkly crystals formed immediately and was removed by filtration and dried to constant weight. Yield 45g 2,4-dimethoxy-N-methylamphetamine hydrochloride (2,4-DMMA)
1. NaOH is added to avoid the decomposition of sodium borohydride in water.
2. The stirring should powerful enough to create a emulsion. This allows the surface area of the two phases to be as large as possible, which means better contact and short reaction time.
Comments
I'm sure about 0,5 molar equivalents sodium borohydride is sufficient. The large amount used here was actually due to a miscalculation on my side.
My firm belief is that the in situ liberation of methylamine is more effective than using a premade 40% aqueous solution. The addition of NaOH to MeAm HCl, using the concentrations above, makes a nearly saturated solution of NaCl at the same time. This kicks out the methylamine from the aqueous phase and forces it into contact with the ketone. If a premade 40% solution is used the amine is much more prone to stay in where it is, thus less of the target imine is formed.
Freaky
(Chief Bee)
06-16-03 17:34
No 440303
(Rated as: good idea!)
For the new members in the audience I probably need to add that the above "wet" method is only suitable for use with N-alkylamines, such as Methylamine/Ethylamine and similar, the yield with ammonium chloride or other ammonium salts is very likely to be sucky.
Barium: However, as you are now pioneering a VERY novel method here using a PTC in the reduction, I believe it would be HUGELY interesting if you could take this method as far as to actually TRY this procedure on something like 10-20 mmol scale, using concentrated ammonia as the aqueous phase. What if the ketone is water-insoluble, and the imine is not? Then the ammonium imine can be selectively reduced even if only a fraction of the added ketone is present in the imine form!
If you decide to go as far as you can go with this idea (I'd love if you could do that), then you could run three 10 mmol experiments in parallell, using the conditions below, and analyzing the resulting alcohol/amine ratio when the starting ketone has disappeared:
1) Your above conditions, but with 2 eq 25% NH3 as the amine (Aliquat 336 is a pretty hydrophobic PTC)
2) As in "1" but using the more hydrophilic tetrabutylammoniumbromide (TBAB) or any other Me/Et/Pr/Bu combo.
3) No PTC, simply running the rxn as a well-stirred two-phase rxn, possibly adding a few drops low-mw PEG if the reaction does not go forward at any reasonable speed.
I guess you understand my reasoning - by choosing a more and more hydrophilic borohydride species, you are treating the ketone in the toluene layer progressively more gently, while hopefully reducing the imine at a reasonable speed, and therefore making it possible to actually reduce an unsubstituted imine using aqueous borohydride.
I don't have more than 25% hope to get more than 25% yield in any of the above reactions, but the time and precursors might be worth risking, considering the immense gain gotten in case you could get even something like a 40% yield of amine this easy. As the reaction conditiona are so mild, any ketone not becoming amine should instead quantitatively become the 2-ol, which in that case can be recycled - possibly in the same pot, by just oxidizing the non-polar toluene solution resulting from extracting the product amine with aqueous acid in the workup. The ketone is then distilled and reused.
(Hive Addict)
06-16-03 18:14
No 440312
Two souls same thought. Before I posted this new reaction is was actually looking for a hydrophilic Aliquat PTC. My memory tells me that there is one in this family which is hydrophilic as opposed to the rest of the family. I'll give your proposed systems a try too.
Freaky
(Chief Bee)
06-17-03 01:57
No 440384
Low molecular weight PEG's are pretty hydrophilic, and if surfactants (like the short-chain pyridine quats), even if not being true PTC's, will work, they are ubiquitous, so that might be worth a try if the "standard" PTC's does not work satisfactorily...
(Newbee)
06-17-03 01:58
No 440385
This is truly one of the greatest advances in clandestine chemistry. Barium may I work for you :). On second thought I'll just bow at your FEAT, get it. Thanks you have made my life so much easier, you will never truly know. Benezaldehyde to ketone, now this, amines almost in one pot, hahahahaha, I love it!
(Daddy)
06-18-03 00:58
No 440615
At last my dream came true after more than 5 years.
A dedicated scientist who simply found a way around forbidden precursors (how clever, and brave) and solved at last the methylamine gas tripwire trap, where so many abandoned the method for too many risks involved.
And what a clever, elegant solution, your perfect way to form the methylamine gas in situ!
And no cooling needed anymore, and the formation of a separate imine solution, hats off!
And then the added value of all your novelties you already offered in the last months.
A true MASTER of the ART.
Your Hydrous PTC Imine Reduction has now officially replaced ALL my boro one pots, what a great step forwards, I feel immens pleasure this very moment, thanks to you!
I just uncorked a bottle of Icewhine to celebrate the wonderfull moment, so, congratulations to you!
I'm waiting in awe for what the future will bring from you to our collective mind, I must admit, I envy you to be able to do this research, I never had the guts to confront the law in my part of the world with what would be a sure head-on collission course.
They would find a way to tackle me, probably in some unsportive manner bending the rules. LT/ , [fuckin happy as hell]
WISDOMwillWIN
(Moderator)
06-18-03 01:49
No 440621
What if the ketone is water-insoluble, and the imine is not? Then the ammonium imine can be selectively reduced even if only a fraction of the added ketone is present in the imine form!
Since the most common characteristic classical reaction of imines is aqueous acidic hydrolysis to reform the carbonyl and amine compounds that originally formed the imine, it seems rather likely that the imine will have greater aqueous solubility than the ketone 
Chemistry is our Covalent Bond
(Hive Addict)
06-18-03 12:14
No 440774
Your kind words make me blush. It warms my heart to see a really competent person appreciate my work. I wish I could have a glass of wine with you.
For the future: I have a couple of really nice things almost completed in the lab. Hopefully those new goodies will drive the DEA mad. At least one of them will be extremly hard for the fuckers to control the production of.. (insert evil grin here)
Freaky
(Chief Bee)
08-15-03 13:37
No 453703
(Rated as: excellent)
Reactions of Sodium Borohydride in Acidic Media.
Selective Reduction of Aldehydes with Sodium Triacetoxyborohydride
By G. W. Gribble and D. C. Ferguson
J. Chem. Soc. Chem. Comm. 535-536 (1975)
Summary
Aldehydes, but not ketones, are smoothly reduced to alcohols with sodium triacetoxyborohydride, prepared from sodium borohydride and acetic acid in benzene.
Although aldehydes are generally reduced more rapidly than ketones by alkali metal borohydrides2,3 and aluminohydrides3,4 and diborane5, the absolute rates of reduction are too fast to take advantage of the inherent relative rate differences between aldehydes and ketones, thereby making the selective reduction of aldehydes impractical. Our recent report1 that aldehydes can be generated from carboxylic acids with sodium borohydride (leading to a new alkylation of amines1,7) suggested that aldehydes and ketones are in fact reduced relatively slowly by sodium borohydride in carboxylic acid media, and that a practical selective reduction of aldehydes was feasible.
Thus, treating a benzene suspension of sodium borohydride (4 eqv.) with glacial acetic acid (3.25 eqv.) and refluxing the mixture for 15 min under nitrogen, after the initial rapid gas evolution subsided (ca. 3 mol of H2 liberated), gave a clear solution of NaBH(OAc)38. To this solution of NaBH(OAc)3, (0.027 mol) was added an equimolar mixture of benzaldehyde and acetophenone 0.007 mol each), and the mixture was refluxed for 1 h.
Workup gave a mixture (87% recovery) of benzyl alcohol, acetophenone, and alpha-phenethyl alcohol, in the proportions (NMR) 100:92:8, indicating complete reduction of benzaldehyde but <10% reduction of acetophenone under the extreme conditions of, excess of, NaBH(OAc)3 in refluxing benzene.
A similar reaction with a mixture of phenylacetaldehyde and dibenzyl ketone gave a mixture (90% yield) containing only ß-phenethyl alcohol and recovered dibenzyl ketone.
On refluxing the benzene solution of NaBH(OAc)3 for 6 h, then adding benzaldehyde, only 8% reduction to benzyl alcohol is found. This is consistent with the self-reduction of NaBH(OAc)3 to ethanol via acetaldehyde as proposed1 for the amine alkylation sequence involving NaBH(OAc)3.
The remarkably mild reducing characteristics of NaBH(OAc)3 may be attributed both to the bulky nature of the reagent and to the inductive electron-withdrawing ability of the three acetoxy groups (
I 0.39)9 which stabilize the boron-hydrogen bond.Although acyloxyborohydride species have been sporadically mentioned in the literature5,8,10 the synthetic potential for these reagents has never been realized.
Notes and References
1 For previous paper in this series, see: G. W. Gribble, P. D. Lord, J. Skotnicki, S. E. Dietz, J. T. Eaton, and J. L. Johnson, J. Amer. Chem. Soc., 1974, 96, 7812.
2 H. C. Brown, O. H. Wheeler, and K. Ichikawa, Tetrahedron, 1957, 1, 214.
3 (a) For reviews, see: H. O. House, 'Modern Synthetic Reactions', 2nd Edn., Benjamin, Menlo Park, Calif., 1972, ch. 2; (b) H. C. Brown, 'Boranes in Organic Chemistry,' Cornell University Press, Ithaca, N.Y., 1972, ch. XII.
4 H. C. Brown, P. M. Weissman, and N. M. Yoon, J. Amer. Chem. Soc., 1966, 88, 1458.
5 H. C. Brown and B. C. Subba Rao, J. Amer. Chem. Soc., 1960, 82, 681.
6 For a review, ref. 3(b) ch. XIII.
7 G. W. Cribble and P. W. Heald, Synthesis, in the press.
8 This species has also been reported to be formed along with sodium diacetoxyborohydride, from triacetoxyborane and sodium hydride: C. D. Nenitzeseu and F. Badea, Bul. Inst. Poluch. Bucuresti, 1958, 20, 93 (Chem. Abs., 1961, 55, 2325).
9 R. W. Taft, N. C. Deno, and P. S. Skell, Ann. Rev. Phys. Chem., 1958, 9, 287.
10 T. Reetz, J. Amer. Chem. So,., 1960, 82, 5039; T. Wartik and R. K. Pearson, ibid., 1955, 77, 1075; J. Inorg. Nuclear Chem., 1958, 7, 404.
(Daddy)
09-07-03 19:02
No 457603
Normal Hive reactiontime policy on groundbreaking novel procedures is up to TWO YEARS!
In this case, I really like to see results and reports from other daring members, to give this beautifull procedure the IMPACT it deserves around especially Newbees.
I just linked this thread in the Newbee forum sticky threads, where I thought it was already linked there by me at the same time I linked it in the sticky one in this forum.
Some one there intended to follow my old procedure again, can you imagine that?!
So feel free to add any own experiences with this method here. LT/
WISDOMwillWIN
(Heavyweight Chempion(eer))
09-13-03 14:32
No 458857
(Rated as: excellent)
1-(2,4-dimethoxyphenyl)-2-propanone, 250 mmol
Methylamine HCl, 375 mmol
NaOH, 375 mmol
Sodium borohydride, 140 mmol
IPA
Water
To a solution of the ketone in 300 ml IPA was added a solution of 25,3 g methylamine hydrochloride in 30 ml water followed by dropwise addition of 15 g NaOH dissolved in 40 ml water during 10 minutes while stirring the mixture violently. When the addition was complete the mixture was stirred for another hour at room temperature.
A solution of 5,5 g sodium borohydride in 20 ml water containing 25 mg NaOH was then added dropwise over 30 minutes while the mixture was stirred violently. When addition was complete the stirring was continued for two hours. The residual borohydride was destroyed by addition of diluted hydrochloric acid (1:5 conc hydrochloric acid:water) until gas evolution ceased and pH 3 was reached. The alcohol was removed by distillation in a rotovap and the aqueous solution diluted with 100 ml water, extracted once with 50 ml toluene, made strongly alkaline with 25% aq. NaOH and then extracted with 2x50 ml toluene. The combined alkaline extracts was dried over MgSO4 and the solvent removed by distillation. The residual oil was dissolved in 200 ml EtOAC and 5N HCl/IPA was added in portions until pH 5 was reached. Several times the acid addition had to be stopped and the formed crystals removed by filtration. The salt was then recrystallised in IPA.
Yield 48,5g N-methyl-2,4-dimethoxyamphetamine hydrochloride (79%).
I discovered some time ago when performing CTH's using aqueous solutions of sodium hypophosphite, Pd/C and EtOAc to reduce phenylnitroalkenes to ketoximes that the reductions didn't start until a few ml's IPA was added. This shows that IPA can act as a PTC. It is also cheaper and more accessible than PEG's or Aliquat's.
The Unworthy
(Moderator)
09-13-03 18:12
No 458881
Maybe IPA acts as a hydride donor or carrier?
(Stranger)
09-14-03 05:37
No 458951
OK, LabTop and Barium.
I for one have used the wet method in the past but not with these groundbreaking results. Also have read with great interest about this method, in my short time on the Hive and have wondered why there seems to be limited interest. Will try it soon and post the findings.
Now, Barium if you could be so kind as to give me some hints on suitable Bayer/Villiger catalysts it would be much appreciated.
(Stranger)
09-14-03 05:52
No 458956
Yes, I know that was incomplete but the other night I typed a long post and it wouldn't go through. So at least I know this is working now.
I started a little thread in Methods on the twodog procedure you might have seen. This is what I am doing now. With sucess I might add. He gave me some very helpful information and Rhodium also as well. As my access to the journals is unavailable at this time I am limited to the internet for guidance.
(Heavyweight Chempion(eer))
09-14-03 14:38
No 459013
I have yet no experience with the Bayer/Villiger reaction.
The Unworthy
(Hive Bee)
12-03-03 12:29
No 474478
OK! So.. if someone had some MDP2P and wanted to use a "A really wet reductive alkylation," would the "Improved wet reductive alkylation" method be suitable?
(Chief Bee)
12-03-03 12:32
No 474479
Yes - just correct for the differences in molar weight of the substrates.
(Stranger)
12-16-03 21:48
No 477228
Can anyone who has performed Barium's NaBH4 hydrous reductive amination (3,4-MDP-2P or otherwise) comment on the scalability and temperature sensitivity (as it relates to increaced scale) of this reaction?
Specifically, swim is interested in how scaling the reaction should effect imine formation time, NaBH4 addition time, and the possible need for external cooling.
Thanks...and bravo, Barium.
(Stranger)
01-07-04 05:22
No 480855
I have been trying to master Barium's wet method, have had mixed results so far but it is probably more due to errors on my behalf than anything else.
i have also been doing these trials scaled up (350g MDP2P) for a couple of reasons;
1) to achieve the prescribed optimum (violent) stirring in my equipment (anything less doesn't stir)
2) i want it to work at this quantity, so may as well try getting it to work from day 1.
Very briefly;
trial one failed due to mainly (i think) my mixing of NaBH4 with water and then the NaOH rather than basifying the water first?
trial two worked ok with approx 200g of MDMA.HCL yielded. (Naturally i am hellbent on increasing this yield but i was ecstatic on the fact that it worked...i am so sick of messy Al/Hg.)
trial three is partly processed but i don't consider at this early stage that it will be successful as trial two due to a strange blue color.
I will post more thorough details tomorrow and if i have complete failure, i will include some photos so that the experts can hopefully pinpoint the errors.
(Chief Bee)
01-07-04 17:56
No 480927
Most of the MDP2P not converted to MDMA will instead have been reduced to MDPol, which will be left in the non-polar phase after the acid/base extraction. This can be isolated, distilled, and then re-oxidized (with chromate, bleach, etc.) to MDP2P and then reused.
The Hive - Clandestine Chemists Without Borders
(Newbee)
01-09-04 09:14
No 481388
Rhodium,
so swim is clear, is this correct for an a/b workup of barium's reaction to isolate both mdp2pol and mdma.hcl?
1. flood reaction contents with water.
2. extract with np. will dcm be fine for mdma fb and
mdp2pol? swim wants to use a volatile np solvent.
3. acidify with aq hcl and separate (will acid only react
with the amine and not the alcohol?)
4. continue a/b workup on aq phase to get mdma
5. evap np to get mdp2pol
will this produce sufficiently clean mdp2pol for oxidation? or must (swim says must, not should) he vacuum distill as mentioned in Post 399715 (Rhodium: "Piperonal -> MDP2NP -> MDP2P -> MDP2Pol", Novel Discourse)? swim asks because he has read many posts that say that mdp2pol rearanges and may be otherwise unstable.
also, is anything else created as a reaction side product other than mdp2pol using this method? swim is trying to find out if anything else will be sucked into the np from the reaction mixture and be there when it evaps off.
(Chief Bee)
01-09-04 20:01
No 481437
(Rated as: good read)
The crude MDP2Pol will be a mess of other byproducts, so it is imperative that you purify it by distillation before carrying on to the oxidation step. Naturally, the MDP2P gotten after the oxidation step also needs to be distilled before use.
How to isolate MDP2Pol, the major byproduct of reductive amination of MDP2P
If you are using the procedure in Post 328680 (Barium: "A really wet reductive alkylation", Novel Discourse) then the MDP2Pol will remain in the toluene phase after the acidification and extraction of it with the 5% HCl.
If you are using Post 458857 (Barium: "Improved "wet" reductive alkylation", Novel Discourse) then acidify as usual and evaporate the isopropanol, then extract the MDP2Pol into the non-polar solvent of your choice.
Regardless of method used above, the MDMA will be in the aqueous phase and the MDP2Pol in the non-polar one. Now wash the non-polar solution with dilute aqueous sodium bicarbonate to remove any remaining acid (which could hurt the MDP2Pol), distill off the solvent, and vacuum distill the residue (preferably with a fractionation column) to isolate the MDP2Pol, bp 125°C/25mmHg (Ref: Post 399715 (Rhodium: "Piperonal -> MDP2NP -> MDP2P -> MDP2Pol", Novel Discourse)).
The MDP2Pol is now ready to be oxidized to MDP2P again, using any known method.
Some suggestions on how to do it:
Post 432203 (Rhodium: "Jones Oxidation of P2Pols to P2Ps", Methods Discourse)
Post 392005 (Aurelius: "Oxidation of alcohols with (NH4)2Cr4O7 in solution", Methods Discourse)
Post 392008 (Aurelius: "P2Pol to P2P", Methods Discourse)
Post 434379 (Megatherium: "To generate P2P from the P2Pol, one could use...", Chemistry Discourse)
Post 367709 (Rhodium: "Phenyl-2-propanol", Chemistry Discourse)
Post 367667 (ChemisTris: "Oxidation of P2Pol - a literature search", Chemistry Discourse)
Post 236500 (Acme: "Ref's for Propylene oxid method", Methods Discourse)
Post 272729 (Rhodium: "Re: Grignard P2Pol In Situ Oxidation", Novel Discourse)
Post 290388 (foxy2: "Here it is", Novel Discourse)
The Hive - Clandestine Chemists Without Borders
(Hive Addict)
01-17-04 04:45
No 482945
By unfortunate circumstances, the NaOH was added BEFORE the MeAM solution, then the MeAm solution was added....
Am I doomed??? or do I still have potential product at the end.. the solution went brownish w/ the NaOH and is now a yellowish orange, w/ MeAm smell present.. please advise ASAP!
Infinite Radiant Light - THKRA
(Old P2P Cook)
01-17-04 07:06
No 482963
Should work the same no matter which of these was added first. I always used methylamine freebase prepared by dissolving methylamine gas in methanol; the solution would turn slighlty yellow as the imine was formed.
All those moments will be lost in time, like tears in rain.
(Stranger)
02-29-04 20:18
No 491839
Decided to give this a try using the Aliquat 336 method instead of the IPA as the Aliquat was readily available and Barium had such high yields with it.
33,54 gr. (250 mmol) phenyl-2-propanone (note 1)
25,3 gr. (375 mmol) methylamine HCl (note 2)
11 gr. (290 mmol) sodium borohydride
4,8 gr. Aliquat 336
In a 1000 ml 3 neck RBF fitted with overhead stainless steel stirrer the ketone in 100 ml toluene was added followed by the additon of the MeNH2 mixed with 30 ml water in one portion. While stirring violently 15 gr. NaOH in 40 ml water was added dropwise over a period of 19 minutes (some ammonia scent escaping from flask at this point).
A few minutes after after the addition of the NaOH a slight pinkish hue was noticed which
seemed to get slightly darker in color as the mixture was stirred for 1 hour at room temp.
After stirring, the mixture was seperated and the aqueous layer discharged. The organic layer was a tranparent purple color. Very pretty, but not expected. Worried at this point.
The purple imine was tranferred to a 1000 ml, 3 neck RBF fitted with the mechanical stirrer used in previous procedure. Added the Aliquat 336 in approx. 4 minutes (had weighed amount in test tube- very viscous). Prepared the borohydride by placing it along with 25 mg NaOH in a beaker and added 35 ml water and swiled by hand for 3 seconds. Added this in one portion to the imine/Aliquat mix and started violent stirring. At this point an exothermic reaction ensued (noticed condensation in the flask). This was confusing as Barium used slight heating to 35 degrees. Stirring was slowed (still very fast though-enough to create emusion) and a cold water bath was applied until temp came down to 40C where it stayed fairly stable until it started to drop after about 20 minutes of stirring. Also, the purple color dissappeared after the addition of the borohydride and the mix was a somewhat cloudy white color which changed to a somewhat golden yellow color as stirring progressed.
After the reaction the residual borohydride was destroyed by adding dropwise a 20% acetic acid soln. until no gas evolved. The aqueous layer was seperated and discharged. The organic layer was extracted with 3x100ml 10% HCl, which was washed with toluene and saturated with NaCl. The soln. was then basified until pH 14. Noticed at this point that there was very little oil present. Perhaps 3-5 ml. Extracted anyway with 2x50 ml toluene which was washed with water and dilute NaCl soln. About 80 ml of the solvent was stripped off before exhaustion set in and called it a night. Suspect wise bees will say to fractionally distill ketone. Please advise and I will give this one another go. -zero
Note 1- made using store bought phenylacetic acid using xtaldocs PbO method [../rhodium /p2p.paa
Seperating the orgaincs in sep funnel, washing the organic layer with 20% NaOH soln. until washing were alkaline to pH paper and then washing organics with water which created a serious emulsion. The emulsion was effectively broken up by adding NaCl to the sep funnel and swirling. The aqueous portion of the post reaction mix was extracted with 2x50 ml portions of diethyl ether, and treated as per organic layer procedure above. The ether extracts were then added to main product, dried over MgSO4, and the ether stripped off. The resulting ketone was vacuum distilled but not fractionationally distilled.
Note 2-made using Vogel procedure. Recrsyallized in methanol. Clear crytals that look snow white when all together in a flask.
(Hive Bee)
03-02-04 06:22
No 492226
In a 1000 ml 3 neck RBF fitted with overhead stainless steel stirrer the ketone in 100 ml toluene was added followed by the additon of the MeNH2 mixed with 30 ml water in one portion. While stirring violently 15 gr. NaOH in 40 ml water was added dropwise over a period of 19 minutes (some ammonia scent escaping from flask at this point).
swim is unfamiliar with meth synths (they're illegal 
) but isn't the intermediate imine unstable in the presense of water? water azeotropes with toluene, true. but that's about two mols h2o per mol toluene.
from swim's understanding, meth reductions must be anhydrous.
(Hive Bee)
03-02-04 06:31
No 492230
Upon completion of your addition of the acetic acid....did you measure the pH of the aqueous layer? From the sounds of things, you have over-acidified and the majority of your freebase has gone into aqueous solution and you have discarded it!
I hope not! First rule of the lab....never discard ANYTHING until you have identified all your expected product.
FanofShulgin
Peace, love and empathy
(Stranger)
03-02-04 20:57
No 492418
Bond_doublebond : not sure if the imine is stable. Questioning the necessity to do this under anhydrous conditions is what this thread is all about. Barium laid the groundwork but other ketones are the big questions in my mind.
Fanofshulgin : No I saved it all. Will check this out and report. Thanks for the reply btw. Doesn´t seem to be much support for those in the trenches. -zero
(Hive Bee)
03-03-04 08:08
No 492573
Bond_DoubleBond: its true that schiff-bases are not very stable in the presence of water (thus why their formation is often carried out under Dean-Stark conditions), but you would be surprised.....the main point is the imine formation is reversible - there is an equilibrium between imine and ketone. The reductive amination is possible due to the basically irreversible reduction of imine to amine. Le Chatillier's principle would suggest that as the imine was consumed (even if slowly) then more imine would be formed.
zero: Let me know how things go. I would try rebasifying the aqueous layer then extracting with organic solvent (DCM or ethyl acetate perhaps).
Fanofshulgin
Peace, love and empathy
(Hive Bee)
03-17-04 10:30
No 495677
Post 458857 (Barium: "Improved "wet" reductive alkylation", Novel Discourse)
Swim followed this post exactly using P2P and methylamine.hcl made from ammonium chloride + paraformaldehyde, and had a problem.
The residual borohydride was destroyed by addition of diluted hydrochloric acid (1:5 conc hydrochloric acid:water) until gas evolution ceased and pH 3 was reached. The alcohol was removed by distillation in a rotovap and the aqueous solution diluted with 100 ml water
After destroying the remaining borohydride swim attempted to distill out the alcohol from the aqueous mixture. However, swim noticed that he had two layers at this point--a bottom aqueous layer and a top layer that is...? Is it unreacted P2P?
It's a possibility that swims methylamine synth was a failure. However, the recrystalized methylamine appears ok, even though it is slightly blue from the otc paraformaldehyde. This is the only thing he can think of that might have caused this?
The reductive amination went perfectly, from what swim could tell, but obviously there was a problem because he didn't get any yield at all.
Swim would appreciate any constructive criticism.
(The Archetypical "Good Guy")
03-17-04 10:44
No 495679
Are you talking about the post reaction mixture, that is made up by two layers?
IPA sometimes separates from water if too much sals is present in the aquous solution. You used methylammoniumchloride + HCl + borohydride, which indeed would give you a very "salty" mixture of this and that. Perhaps it's simply the alcoholic layer floating on top?
Regards
Bandil
Nuke the whales!
(Hive Bee)
03-17-04 11:21
No 495687
Ahh.. I didn't know that! That would make sense. I was thinking that was the case at first, but after I looked up the solubility of IPA in H2O I disregarded that thought.
Swim separated the two layers and proceeded to work up the aqueous phase, with no product at all. Swim saved the other phase and will maybe try to work it up later. In order to work it up, if it is IPA after all, you would have to add some water and distill of the IPA first, correct? Damn! That's exactly what Barium described, swim just got confused
.Thanks for the reply!
(Stranger)
03-17-04 18:58
No 495764
The "improved procedure" was tried with p2p (250 mmol,fractionally distilled under reduced pressure,very pale yellow,light scent) and recrystallized MeNH2 (absolutely clear crystals).
Upon addition of the NaOH in H2O to liberate the freebase a salt precipitated out of the liquid which stuck to the sides of the flask accompanied by the strong scent of MeNH2 freebase. Guessing that the salt is NaCl. The alcohol was stripped via vac distillation and at this point a pale violet color was noticed in reaction mix. Violet colored substance seperated to top in sep funnel and was extracted into the toluene wash. The reaction mix was basified, extracted with toluene, the toluene removed via vac distillation and the clear oil (19 grams) was acidified with aqueous HCL, the water boiled off, and the liquid was poured into freezing cold dry acetone. Crystals precipitated immediately. However there was also a strange looking wax like substance which stuck to the sides of the glass in small globs. There was alot of the waxy substance. Yield of good substance not yet determined. The procedure works but most likely needs fine tuning by a chem badass. Unsubbed ketone may require a special procedure. -zero
(Newbee)
04-01-04 10:34
No 498443
Sorry for being noobish but can this be used re: dialkylamines?
Like, some synths requiring a low bp amine like dimethylamine might be easier to control (re:condensation of dimethylamine) when holding it in reflux with a high bp solvent.
Could this be achieved better using the wet alkylation method by say, holding the solvent containing the reactant + hydrochloride salt of dimethylamine and when reflux is reached, slowly add NaOH? Surely freebasing the amine in the solution should yeild better due to surface area, 'cuz more amine reacts with the other interesting chems before heating up to a point where it boils out of soln.
Any comments? Can this be done?
(Stranger)
04-16-04 19:30
No 501092
Looking at Bariums original post (458857), the molar ratios were .25: .375 : .375 : .14 but looking at the quantites he used there, the MeHCL was much greater and the Sod Bor a bit higher as well.
What ratio did Andromeda use for the 350g (292.8 mL ?) ( 1.96 mol) batch? And did 2000mL IPA suffice ?
Would like to try the procedure, but could use some guidence on these points. Thanks much
(Stranger)
06-06-04 13:18
No 511760
When I tried the wet alkylation method I kept ending up with 75% mdpdp-ol and 25% mdma. I have therefore been concentrating on labtop's anhydrous me.am method with great results. I concede that it is more work but it is simple.
I will have another go soon. Doesn't seem to be much discussion about this method considering the support that it is a breakthru?
(Stranger)
07-04-04 00:11
No 517249
was there a scale up for this route to be successful? any bee had any experience with scale up?
oops i did it again
(Newbee)
07-04-04 07:07
No 517335
Thought this might be relevant to this thread: From "Modern Synthetic Reactions" - Herbert O. House (pg. 53)
"it is customary in hydride reductions to employ a slight excess of the reducing reagent in the event that some of the metal hydride is unintentionally destroyed by reduction with hydroxyl-containing materials present in the reaction medium...It should be noted that acidification of reaction solutions containing excess sodium borohydride can generate diborane which may cause further undesired reduction of groups in the initial reaction product."
ref. J.A. Marshall and W.S. Johnson, J. Org. Chem., 28, 595 (1963).
(Hive Bee)
08-11-04 09:15
No 524776
To a solution of the ketone in 300 ml IPA
What is the purity of the IPA? 91% or 99+%?
Can any experience bee tell us as it might make the mixture containing more water for the 91% version. 9% of 300ml would be 27ml. That's about double of the NaBH4 solution.
Appreciate the answer.....
oops i did it again
(Newbee)
08-12-04 02:05
No 524910
Perhaps you could just dissovle your methylamine in the 91% "wet" IPA and add a little extra water if necessary.
(The Archetypical "Good Guy")
08-12-04 08:46
No 525004
How about just drying your IPA with some epsom salt or something akin, prior to its use? This will give you 99% IPA... The less water in the reaction the better.
Regards
Bandil
Cocaine blows!
(Hive Bee)
08-13-04 05:11
No 525182
hi Bandil,
SWIM used 99+% IPA(reagent grade) for his previous 5 aminations, all yielded 0% or extremely low yield(>10%). SWIM thought that it might be the NaBH4 and NaOH/methylamine salt were too "salty"(too concentrated), some white crystals often deposited at the bottom of the flask.
SWIM is now keen to find out what was the percentage of IPA used in those successful aminations(yielded more than 40%).
SWIM will give it another go, using aliquat 336, toluene as solvent method.
oops i did it again
(Hive Bee)
09-10-04 22:02
No 530688
Username: Barium
Title: Hive Addict
Subject: PTC - imine reduction
Post:
It seems like there is no great benefit from anhydrous conditions anymore, unless one wants to squeeze out the highest possible yield.
1-(2,4-dimethoxyphenyl)-2-propanone, 250 mmol
Methylamine HCl, 375 mmol
NaOH, 375 mmol
Sodium borohydride, 290 mmol
Aliquat 336, 5 mol%
Toluene
Water
To a solution of the ketone in 100 ml toluene was added a solution of 25,3 g methylamine hydrochloride in 30 ml water followed by dropwise addition of 15 g NaOH dissolved in 40 ml water while stirring the mixture violently. The addition of NaOH was allowed to take five minutes so the liberated methylamine had time to react with the ketone instead of being pushed out of solution. When the addition was complete the mixture was stirred for another hour at room temperature. The aqueous layer was then separated and discharged.
To the toluene solution of the imine was added 4,8 g (12 mmol, roughly 5 mol%) Aliquat 336 followed by a solution of 11 g sodium borohydride in 35 ml water containing 25 mg NaOH1 in one portion. The mixture was violently stirred2 for one hour at 35?by slight warming. The residual borohydride was destroyed by addition of diluted acetic acid until gas evolution ceased and the aqeous layer separated and discharged. The toluene solution was extracted with 3x100 ml 10% HCl and the extracts combined, washed with 50 ml toluene and saturated with NaCl.
The aqueous solution was then made alkaline with NaOH until pH 14 was reached and extracted with 2x50 ml toluene. The combined toluene extractions was washed once with water and once with brine, and then dried over MgSO4. The solvent was removed at 40?@ 80 mbar leaving a slightly yellow oil weighing 48 g (92%). The hydrochloride was made by dissolving the free base in 250 ml EtOAc and adding 5N HCl/IPA until pH 4 was reached. Sparkly crystals formed immediately and was removed by filtration and dried to constant weight. Yield 45g 2,4-dimethoxy-N-methylamphetamine hydrochloride (2,4-DMMA)
1. NaOH is added to avoid the decomposition of sodium borohydride in water.
2. The stirring should powerful enough to create a emulsion. This allows the surface area of the two phases to be as large as possible, which means better contact and short reaction time.
Comments
I'm sure about 0,5 molar equivalents sodium borohydride is sufficient. The large amount used here was actually due to a miscalculation on my side.
My firm belief is that the in situ liberation of methylamine is more effective than using a premade 40% aqueous solution. The addition of NaOH to MeAm HCl, using the concentrations above, makes a nearly saturated solution of NaCl at the same time. This kicks out the methylamine from the aqueous phase and forces it into contact with the ketone. If a premade 40% solution is used the amine is much more prone to stay in where it is, thus less of the target imine is formed.
For this method, can tetra-n-butylammonium bromide, TBAB be used instead of the Aliquat 336?
oops i did it again
(Hive Adickt)
09-12-04 19:53
No 531027
I'm sure it will work as well.
Actual I'm quite sure that Bandil have a post where he don't use anye PTC, red he's post's first.
(Hive Bee)
09-16-04 16:45
No 531613
Hi Hest,
Thanks for the comment.
SWIM has read it many times, during SWIM's meals too. SWIM will try bandil's mol sieves method once he gets the methylamine solution.
As for the method outlined, without PTC, the amount of each chemical used is very sensitive towards the resulting yield. Eg, the amount of H20 used is the major thing, if the solution is not salty(concentrated) enough, not enough methylamine gas is pushed to the IPA, thus affecting yield. If the NaBH4 used is slightly more, the water is not able to dissolve all. SWIM has got extreme low yield(range from 0% to 10% m/m if you wanna know) when using a mechinical weighing machine which is not very sensitive to weighing things at 10g scale. SWIM purchased a digital weighing machine, with 0.1g increment. All followed to the letter outlined in the post. Yield was around less than 15%. SWIM was very happy and that was some improvement. SWIM tried to use IPA 91%(all previous used was 99.7% claimed by manufacturer), highest yield was about 40%. SWIM has tried to vary the method to give optimum output but failed. Oops, SWIM is not going to declare it fail yet. SWIM will try until he gets good result, with repeatability.
Now, SWIM has planned to use other solvent, toluene is in the list, ethanol, DCM, DMF are some others. SWIM has no experience with PTC at all, thus the previous post.
Please forgive SWIM's lack of knowledge and asking a lot of stupid quetions.
By the way, did you(hest, hive addickt) produce the same result using aq. solvent? If yes, can you please be kind enough to share what are the tips in achieving the mentioned yield. SWIM firmly believe that it is achievable, thus has performed so many aminations.
Anyway, SWIM has replaced the IPA method using methanol as solvent, generating methylamine gas in situ. Has got his yield shoot up.
oops i did it again