finetune - 20-11-2019 at 13:31
Good evening!
As I have some cinnamic aldehyde on the shelf I thought about reducing the double bond to get hydrocinnamic aldehyde.
At first I found the CTH article, but noting about a CTH reduction in acidic media, as the alkali will result in an unwanted aldol condensation.
Catalytic transfer hydrogenation of cinnamic acid in alkaline aqueous medium using PdCl2/HCOOH/NaOH
https://doi.org/10.1016/S0040-4039(00)01365-4
I came to the result to use a catalytic hydrogenation with 5% Pd/C in EtOH at low hydrogen pressure and preferably ambient temperature. but on further
reading I became more confused the more I read. There is a shitload of articles regarding the catalytic reduction of alpha beta unsaturated aldehydes,
most of the ones I had on the screen dealing with the selectivity of certain catalysts. That´s also why I became more and more confused (and most
probably because I made the mistake of not taking notes).
The main question still in my head is about the solvent. I remember reading somwhere that the solvent can have a (high?) influene on the selectivity
of the reduction. I would use 96% EtOH or anh. MeOH.
At the moment my conditions would be:
Cinnamic aldehyde
10 vol. eq. 96% EtOH or MeOH
1 to 5 mol% 5% Pd/C
3-5 bar H2
20°C
I tested my reactor up to 15 bar, 150°C, so this should be no problem here. If somebody has a grat catalyst wich requires higher pressure, I can
build the reactor myself. I have quite a lot of metals in my collection, but no Raney alloy for example.
Ideas and suggestions are welcome!
Finetune
[Edited on 20-11-2019 by finetune]
finetune - 20-11-2019 at 14:27
I just found an article wich describes Pd/C poisoned with diphenyl sulfide.
It´s pretty much what I was looking for 
Chemoselective Hydrogenation Method Catalyzed by Pd/C Using Diphenylsulfide as a Reasonable Catalyst Poison
DOI: 10.1016/j.tet.2006.09.094
Corrosive Joeseph - 20-11-2019 at 14:29
3-phenylpropanal literature search
https://www.sciencemadness.org/whisper/files.php?pid=501805&...
/CJ
finetune - 20-11-2019 at 15:08
Forum response on opening the link:
"Sorry, you are not permitted to view this forum"
Why is that?
Corrosive Joeseph - 20-11-2019 at 15:22
Oops, you need access to References and whimsy....... But I should have known that. (facepalm)
Here it is again - https://ufile.io/9oxr29k4
/CJ
S.C. Wack - 20-11-2019 at 18:15
NaBH4 is the preferred way to make Pd catalysts. And Pt, and Ni...but in this case...Pd.