Author Topic: DOB starting from 4-br-2,5-dmeObz  (Read 1517 times)

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silenziox

  • Guest
DOB starting from 4-br-2,5-dmeObz
« on: February 04, 2004, 08:37:00 AM »
The following will be conducted in few weeks as the timetable forbids, so to say.. The synth is following the writeup found at

https://www.thevespiary.org/rhodium/Rhodium/chemistry/mda.txt


I let you know the yields  ;)  ... and all comments/suggestions are welcome!

STEP 1 (Makin' da nitroalkene)

Dissolve 500g (2.05mol, 245.07g/mol) of 4-bromo-2,5-dimethoxybenzaldehyde into 154g (2.05mol, 75.067g/mol, Density: 1.045) of nitroethane containing 33g of cyclohexylamine and let the mix stand for about 3 weeks... Then, crush your nitroalkene cake and wash it with about liter of freezer cold MeOH. Spread to dry...

Supposed YIELD: ABOUT 500-550g of 4-bromo-2,5-dimethoxyphenyl-2-nitropropene (288.095g/mol)

STEP 2 (Reducin' da above mentioned stuff with AlH3)...

To 250 g of LiAlH4 dissolved in 3,5 L of ice cold anhydrous THF or in 2L of anhydrous diethyl ether, add dropwise with cooling and stirring and to this, 48ml of 100% H2SO4 (keep under 0'C!). To the reducing solution, add 500-550 g of 4-Br-2,5-DiMeOP-2-NP (straight from the previous step) dissolved in 1 L of anhydrous THF or diethyl ether... The addition should take around 4 hours with proper cooling (keeping below 0'C) of the reaction mix...

Stir at room temperature for 48 hours... (NO REFLUX!) Check the completion of the reaction with TLC...

Then, add to the mix containing the now reduced compound, 1000 ml of IPA to decompose the residual AlH3... followed by 400 ml of ~20% aqueous NaOH... (100g NaOH)

Filter the solids (Al + Li salts) from the reaction mix and CAREFULLY wash the filter cake using first some THF and then with IPA...

Evaporate the solvents and (preferably distill the oil) gas the free base in anhydrous IPA with HCl or add 1:1/mol 85% phosphoric acid to get the monobasic phosphate.

Afterwork: Wash the salt with anhydrous Et2O and recrystallize from boiling IPA.


Novice

  • Guest
Why H2SO4?
« Reply #1 on: February 04, 2004, 11:46:00 AM »
Won't the sulphuric acid destroy LiAlH4 in a very explosive manner? Thus eliminating its reductive properties...

If IPA with its very weakly acidic O-hydrogen is used to destroy excess LiAlH4 when the reduction is over, then concentrated sulphuric acid most definately should destroy the LiAlH4 before addition of the substrate.

LiAlH4 + 2 H2SO4 =>  Li- + Al3- + 3 H2 + 2 SO42-

Correct me if I'm wrong.

[Post edited moments after posting; empirical formula of LiAlH4 corrected :-]

indium

  • Guest
The trick is to add just enough h2so4 to form...
« Reply #2 on: February 04, 2004, 01:37:00 PM »
The trick is to add just enough h2so4 to form the alane..


But 200gr of DOB is enough to send a moderately large city to la-la-land.

Rhodium

  • Guest
LAH to Alane
« Reply #3 on: February 04, 2004, 04:15:00 PM »
2 LiAlH4 + H2SO4 -> H2(g) + Li2SO4(s) + 2 AlH3


hest

  • Guest
Hoho
« Reply #4 on: February 05, 2004, 04:39:00 AM »

To 250 g of LiAlH4



Have fun. 

Stick to NaBH4 and some sort of nitro red. (Al(Hg)-NH4COO/Pd/C-Zn/AcOOH ect.)


Lilienthal

  • Guest
Addition in the cold is VERY dangerous!
« Reply #5 on: February 05, 2004, 04:59:00 AM »
Addition in the cold is VERY dangerous! It will most probably result in an uncontrollable exothermic reaction (= big fireball), especially on such a mega-scale. Only suicidal / killer personalities would try such a reaction without a scaling-up process from sub-gram amounts.

silenziox

  • Guest
Mad Hatter in the Wonderland
« Reply #6 on: February 06, 2004, 03:01:00 AM »
Lili: Addition in the cold is VERY dangerous! It will most probably result in an uncontrollable exothermic reaction (= big fireball), especially on such a mega-scale.

Whaaat? What's the difference performing the reaction inside with ice-bath or doing it outside with snow cooling the reaction and keeping the temperatures below 0 degrees (stirring the solution vigorously, adding one drop at a time and waiting until the solution has cooled back to 0?

Anyways I'll be using argon/nitrogen blanket for preventing the possible flames to get enough oxygen to burn...

What comes to the usage of ether in the synth, that might be not so good idea, as it really has to be 110% anhydrous.. If it isn't, the fuckup is imminent.

Lili: Only suicidal / killer personalities would try such a reaction without a scaling-up process from sub-gram amounts.

Yes! My motives are to conquer the world! Nothing will stop me from my 1000-year reign!! I guess it's time for changing my title?  ;)

indium:But 200gr of DOB is enough to send a moderately large city to la-la-land.

I'm expecting around 400g yield from this ;)  

I liked my idea to make the synth even more mega-scale, couple of kilos of the benzaldehyde, but I unfortunately broke my rotavap during the distillation of the nitropropene  >:(

(200g is quite low scale anyways, how'd they do amphetamine in the big scale anyways?)


hest

  • Guest
Re: but I unfortunately broke my rotavap ...
« Reply #7 on: February 06, 2004, 03:26:00 AM »

but I unfortunately broke my rotavap during the distillation of the nitropropene




Ohh and now I'm rely trust your post-


Bandil

  • Guest
I'm assuming that he is referring to the ...
« Reply #8 on: February 06, 2004, 03:45:00 AM »
I'm assuming that he is referring to the removal of the solvent using a rotovap, and not distillation of the NP  :)


silenziox

  • Guest
Thanks Bandil... Always tell I'm distilling...
« Reply #9 on: February 06, 2004, 08:38:00 AM »
Thanks Bandil... Why do I always tell I'm distilling the nitrocompound  :)  (watch out for the PM)  ;)

Wont the NaBH4 dehalogenate the compound? That is the main reason I'd do the reduction with alane (thanks for rhodium about this info)  :)


Nicodem

  • Guest
Wont the NaBH4 dehalogenate the compound?
« Reply #10 on: February 07, 2004, 03:07:00 AM »
Wont the NaBH4 dehalogenate the compound? That is the main reason I'd do the reduction with alane

No, the NaBH4 don't dehalogenate the arylbromides. It takes a 'stronger' hydride carier like LiAlH4 in aprotic solvents to dehalogenate it.