dormouse (Member)
04-20-00 02:36
No 108325
      Ephedrine to desoxyephedrine - NaBH4 -Rhodium  Bookmark   


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Author  Topic:   Ephedrine to desoxyephedrine - NaBH4 
Rhodium
Administrator   posted 05-11-98 06:28 PM          
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Synthetic Communications. 19(17), 3051-3054 (1989)
(pseudo)Ephedrine, or rather its O-Acetyl ester, is reduced with a large excess of NaBH4/NiCl2 for 30-60 min at room temp to yield desoxyephedrine in 80-90% yield.

Interesting. Sure beats HI/P. Maybe something for TS II if someone gets it to work.


CyderJack
unregistered   posted 05-11-98 09:27 PM           
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Do you mean Sodium Borohydride which I have seen as NaBH3 , is this different from the NaBH4 you are referring to ?

Thanks ,

CyderJack


Osmium
Member   posted 05-12-98 04:13 AM          
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NaBH3 does not exist.
 
Osmium
Member   posted 05-12-98 04:13 AM          
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NaBH3 does not exist.
 
quirks
Member   posted 05-12-98 08:50 AM          
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And the best (standard) way to obtain the ester??
(from the journal)

a. solvent: anyhyrous MeOH
b. Rx temp: room temp
c. Molar ratio: Substrate / NaBH4 / NiCl2 = 1 / 14 / 7

This would work, with crappy yeilds, for just ephedrine too no?


quirks
Member   posted 05-12-98 08:50 AM          
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And the best (standard) way to obtain the ester??
(from the journal)

a. solvent: anyhyrous MeOH
b. Rx temp: room temp
c. Molar ratio: Substrate / NaBH4 / NiCl2 = 1 / 14 / 7

This would work, with crappy yeilds, for just ephedrine too no?


Osmium
Member   posted 05-13-98 05:20 AM          
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Prepare the ester with acetic anhydride, when you can locate some, or use glac. AcOH/H2SO4.
 
Osmium
Member   posted 05-13-98 05:20 AM          
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Prepare the ester with acetic anhydride, when you can locate some, or use glac. AcOH/H2SO4.
 
Rhodium
Administrator   posted 05-13-98 03:48 PM          
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How would you prevent acetylation of the amine? It cannot be too sterically hindered, can it?
 
Rhodium
Administrator   posted 05-13-98 03:48 PM          
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How would you prevent acetylation of the amine? It cannot be too sterically hindered, can it?
 
Lone Ranger
unregistered   posted 05-13-98 09:19 PM           
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I have read of NaBH4 or KBH4 used to supposedly fully reduce the ester formed with H2SO4 in Ephedrine. I doubt it, and have not 'dreamed' of this. I do have a great interest in any possiblilities in this direction...
However, I am wondering if the acid chloride will reduce with either of the fore mentioned reagants. I have had many pleasant dreams about direct hydrogenolys in alkaline over Pd, and high yield dreams of catalytic dehalogenation. I would happily share dreamy details if anyone could help me fiqure out something to do with a few hundred grams of borohydride....


Lone Ranger
unregistered   posted 05-13-98 09:19 PM           
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I have read of NaBH4 or KBH4 used to supposedly fully reduce the ester formed with H2SO4 in Ephedrine. I doubt it, and have not 'dreamed' of this. I do have a great interest in any possiblilities in this direction...
However, I am wondering if the acid chloride will reduce with either of the fore mentioned reagants. I have had many pleasant dreams about direct hydrogenolys in alkaline over Pd, and high yield dreams of catalytic dehalogenation. I would happily share dreamy details if anyone could help me fiqure out something to do with a few hundred grams of borohydride....


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