frogfot
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alkene and ester reduction
I'm wondering if there's some general procedure for reduction of an alkene and ester groups (in same molecule) in one pot..?
I've found buttloads of references for separate reduction of these two groups, and none of methods overlap... except for Li/NH3 that can reduce both
the alkene and the ester but this is not much fun method.. 
Reduction of alkenes mostly include use of hydrogen in presence of transition metal catalysts (Pd, PtO2 etc), while reduction of esters goes with the
usual hydride donors (aluminium and boro hydrides)..
It seems that BH3 can do the job but I'm not sure on the red of alkene.. have no scifinder at the moment...
Any help appreciated.
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Sandmeyer
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To reduce an isolated C=C the best bet would be hydrogenation, of course (for examples browse orgsyn). It is however possible to use hydrides in combo
with transition metals even if the C=C is not activated by electron-withdrawing group, see following papers:
J. Choi, N. M. Yoon, Synthesis, 597 (1996)
B. Ganem, J. O, Osby, Chem. Rev. 86, 763 (1985)
J. malek, Org. React. 34, 1 (1985)
R. C. Wade, J. Mol. Catal. 18, 273 (1983)
Ester can conveniantly bee reduced to alcohol in high yield using more or less OTC reagents:
decanoic acid methyl ester ---NaBH4/THF/MeOH--> decan-1-ol
Yield: 90%
Ref: Soai, Kenso; Oyamada, Hidekazu; Takase, Masako; Ookawa, Atushiro; Bull. Chem. Soc. Jpn.; 57; 7; 1984; 1948-1953.
decanoic acid methyl ester ---NaBH4/I2/THF/0.5h--> decan-1-ol
Yield: 89%
Ref: Prasad, A. S. Bhanu; Kanth, J. V. Bhaskar; Periasamy, Mariappan; Tetrahedron; 48; 22; 1992; 4623-4628.
EDIT: As it happens -- ziqquratu has uploaded this paper recently ( https://sciencemadness.org/talk/viewthread.php?tid=5452 ): http://rapidshare.de/files/15304956/NaBH4.I2_Reductions.pdf....
Another cheap option is sodium in ethanol: Noller; Gordon; J. Am. Chem. Soc.; 55; 1933; 1091. (haven't checked the details here though)...
[Edited on 25-3-2006 by Sandmeyer]
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frogfot
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Thanks Sandmeyer. I checked the references (the second ref didn't work for some reason and I'll check the org. react. on monday).
| Quote: | Ester can conveniantly bee reduced to alcohol in high yield using more or less OTC reagents:
decanoic acid methyl ester ---NaBH4/THF/MeOH--> decan-1-ol
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But this condition wouldn't reduce the alkene..
The problem was to find reducing conditions that are common for both alkenes and esters.. In places where they mention use of transition metal hydride
complexes they're reducing only alkenes, so it's not clear how the ester will be affected in these conditions.. For example it may get reduced to
ether or even to -CH3  (lol, highly unlikely), and it would suck.
One would probably just test this out, but I was thinking that there was some general procedures...
As I understand the metal-borohydride complex has to be ordered. I've seen other ref where they prepare similar reagent by heating NaH with FeCl3 in
THF and gradually adding tBuOH:
Tetra. lett., 45, 3947, 1977
(still, they're talking only about reduction of alkenes)
In your last link one gets similar product as with BH3. The question is if the added borone could be somehow substituted by H and not by OH (in the
second oxidation step)... that is to get RCH2-CH2R instead of RCH2-CH(OH)R.
[Edited on 26-3-2006 by frogfot]
[Edited on 26-3-2006 by frogfot]
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Sandmeyer
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| Quote: | Originally posted by frogfot
Thanks Sandmeyer. I checked the references (the second ref didn't work for some reason and I'll check the org. react. on monday).[Edited on 26-3-2006
by frogfot] |
Here it is:
Synthetically useful reactions with metal boride and aluminide catalysts
Bruce Ganem, John O. Osby
Chem. Rev.; 1986; 86(5); 763-780.
http://rapidshare.de/files/16458203/Synthetically_useful_rea...
Off-topic: Btw, since you can acsess Synthesis then Syntlett works too -- could you upload this paper, please: S. Yoo, S. Lee, Syntlett, 419 (1990)
For some reason I can't download full-texts with my trial account... Paper is about the reduction of aliphatic nitro groups to amines with NaBH4-CuSO4
system.
[Edited on 26-3-2006 by Sandmeyer]
[Edited on 26-3-2006 by Sandmeyer]
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Sandmeyer
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| Quote: | But this condition wouldn't reduce the alkene..
The problem was to find reducing conditions that are common for both alkenes and esters.. In places where they mention use of transition metal hydride
complexes they're reducing only alkenes, so it's not clear how the ester will be affected in these conditions.. |
Actually the "off-topic" paper I requested above might be of interest to you:
http://rapidshare.de/files/16505911/419.pdf.html (tnx Nicodem)
Styrene is reduced to ethylbenzene with NaBH4-CuSO4, the same system is also capable of reducing esters to alcohols. Olefin-reduction requires a bit
harsher conditions (a 3h reflux), so the ester gets reduced first followed by C=C. I see no reason why this wouldn't work for your purpose.
Isn't it compleatly amazing how versatile reagent NaBH4 is? 
[Edited on 27-3-2006 by Sandmeyer]
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frogfot
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Oh, I was late there.. :/
Strange that they didn't mention the reduction of nonconjugated double bonds.. (in NaBH4-CuSO4 paper). But in general this synth seems to be very
nice!!
The review is a nice read. There they get high yields on olefins using LiAlH4-FeCl2 and the procedure is as simple as the above one  Alot of things to test there..
But then they say that the active stuff here is FeAl2.. dunno if it's able to reduce esters :/
| Quote: | Isn't it compleatly amazing how versatile reagent NaBH4 is?
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Wonder how they originally come up with such new properties of these reagents.. huh, maybe mixing them with random stuff and look what happen..
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