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Leuckart reaction

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methlab:
1st Leuckart result:

In a 250ml rbf: 15.5g MDP2P (via buffered performic) was heated with 45g formamide/ammonium formate for 5 hours at around 170C (with liebig on top). Some crystals formed in liebig condenser, but this should not be a problem. Added 75ml H2O and let cool, then added 100ml DCM for extraction. Saved DCM and discarded the greenish/yellowish waterlayer.
Distilled of DCM, added 7ml MeOH and 45ml 15% HCl and heated for 2 hours at around 100C. Washed the very dark solution 2x with 50ml DCM, which took up a lot of the dark shit.
Now i added 20% NaOH until freebase fell out. (white waterlayer on top, golden freebase at bottom of sepfunnel). Yield of raw mda freebase: around 10g. Extracted waterlayer with 20ml DCM, to get everything out and added to raw freebase. Added an extra 150ml DCM and extracted base into DCM. Stripped of DCM and H2O and vacuumdistilled the rest. At around 145C (water aspirator) 8g of very pure whaterwhite mda freebase came over, which i dissolved in 200ml toluene and gased with the old hcl generator. They are a little bit wet now, so i can not tell you the exact weight, but it should be around 8g.
Any comments to improve my knowledge?

greetings & thanx

ning:
You should read the threads I posted!

Hydrolysis after leuckart is important to yields! And for best yields, do not separate the N-formyl derivative. After heating for awhile, directly add NaOH solution and reflux awhile to hydrolyze in-situ. THEN extract and measure yield.

That's my suggestion.

Also, I remember hearing that for best yields, the leuckart should bee started cool and run long. Think about it.

armageddon:
Also, I remember hearing that for best yields, the leuckart should bee started cool and run long. Think about it.

You mean like slowly going up to 160°C for 5 hours, then VEEERY slowly let climb to 185 over next 4 hours? Using a dean-stark trap prefilled with (ketone-saturated) water (and removing formed H2O continuously like in Antoncho's Leuckart thread)..

...but with at least 2 equivalents NMF/Formamide, and just a tiny amount more conc. formic acid, like 1.1 eq. (instead of formate salts) to achieve acidic conditions (pH 4.5 - do I remember right?)

- Or would you suggest other parameters? (for [n-alkyl]-formamide, not using formate salts!)

"Leucky links" on the topic...


Post 452346 (grellobanans: "Leuckart-Wallach Rxn Time Clarification", Newbee Forum)
Post 358528 (missing) (GC_MS: "Leuckart", Stimulants)
Post 302161 (missing) (Antoncho: "Leuckart with 92%+ overall yield", Methods Discourse)
Post 484080 (gandalf: "Leuckart reaction", Newbee Forum)
Post 258333 (LaBTop: "Basic Leuckart OTC", Methods Discourse)
Post 477678 (r2e3: "MDA synth using formamide", Newbee Forum)
Post 382501 (Rhodium: "Leuckart-Wallach Reductive Amination @ 50-70°C", Novel Discourse)
Post 438120 (grellobanans: "Formyl MDA, and crystallization", Newbee Forum)
Post 102118 (missing) (LaBTop: "Leuckart : HUGE scale --> MDMA", Chemistry Discourse)
Post 102756 (missing) (Jo Blo: "N-methy formamide synthesis needed PLEASE", Chemistry Discourse)
Post 398392 (flipper: "leukart", Methods Discourse)
Post 374454 (missing) (madprosr: "how to turn your leukart to shit", Newbee Forum) (how NOT to do it  :P )


Kinda wierd, but although having spent lots of time with searching, I wasn't able to get to a satifying answer for my question - although the leuckart is probably one of the best-discussed reduction methods at the hive - but regarding correct heatup times, the opinions seem to differ widely... ::)

any more input for me brain cells?

Greetz, A

DoctorFeelgood:
In a 250ml rbf: 15.5g MDP2P (via buffered performic) was heated with 45g formamide/ammonium formate for 5 hours at around 170C (with liebig on top). Some crystals formed in liebig condenser, but this should not be a problem. Added 75ml H2O and let cool, then added 100ml DCM for extraction. Saved DCM and discarded the greenish/yellowish waterlayer.
Distilled of DCM, added 7ml MeOH and 45ml 15% HCl and heated for 2 hours at around 100C. Washed the very dark solution 2x with 50ml DCM, which took up a lot of the dark shit.
Now i added 20% NaOH until freebase fell out. (white waterlayer on top, golden freebase at bottom of sepfunnel). Yield of raw mda freebase: around 10g. Extracted waterlayer with 20ml DCM, to get everything out and added to raw freebase. Added an extra 150ml DCM and extracted base into DCM. Stripped of DCM and H2O and vacuumdistilled the rest.

Hydrolysis after leuckart is important to yields! And for best yields, do not separate the N-formyl derivative. After heating for awhile, directly add NaOH solution and reflux awhile to hydrolyze in-situ. THEN extract and measure yield.

Can one please clarify the (blue) hint (from ning), which belongs to the (red) synth above ?
When should i add the NaOH (after the 5 hours, instead of HCl ?), do i  have to use more, because n-formylderivate not separated,...

thanx in advance

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