nleslie321
Hazard to Self
Posts: 62
Registered: 7-11-2017
Location: krakatoa
Member Is Offline
Mood: just right
|
|
De-protection of N-Benzyl groups
So im trying to de-protect a N-Benzyl group using 5% Pd/C and having no luck. Since reading up im seeing that 10% Pd/C is normally used. But then im
also seeing that in certain types of compounds even 10% Pd/C is not enough and have seen papers using a combination of 15% Pd/C and 15% Pd(OH)/C to
remove the benzyl group. Also as i have like 25g of 5% Pd/C is it possible to use a molar excess of 5% Pd/C to have the same reactivity as what 10%
Pd/C has?
|
|
|
AvBaeyer
National Hazard
Posts: 644
Registered: 25-2-2014
Location: CA
Member Is Offline
Mood: No Mood
|
|
What kind of N-benzyl group? What solvent are you using? What is the hydrogen source (tank or home generated)? What pressure are you using? Stirring
or shaking? These are all variables which are needed to know before any useful answer can be offered.
AvB
|
|
|
nleslie321
Hazard to Self
Posts: 62
Registered: 7-11-2017
Location: krakatoa
Member Is Offline
Mood: just right
|
|
Im trying to remove benzyl group attached to a piperidine based compound. I was trying to do a catalytic transfer hydrogenation using ammonium
formate. I can make hydrogen via water with electrolysis and do it under pressure of a balloon with stirring. I think i need 10% Pd/C from research
ive done. My question is can i double the amount of 5% Pd/C to compensate for 10% Pd/C. Thanks for any help ive not had to ask anything before as i
can find everything i need to know for books, papers or on websites such as this one etc.
|
|
|
AvBaeyer
National Hazard
Posts: 644
Registered: 25-2-2014
Location: CA
Member Is Offline
Mood: No Mood
|
|
The information you have provided is still too vague to give a specific answer so I will give you some general information. In order to remove a
typical N-benzyl group from an amine you will need to run the reaction in an acidified solution. Typically this is done in ethanol containing at least
enough HCl to neutralize the amine. This is done as free amines can act as mild catalyst poisons for Pd-C. Methanol as solvent is generally not
recommended as it can catch fire on mixing with the catalyst or when working up the reaction. Perhaps you could retry your ammonium formate reaction
in acidified solution. Hydrogenation under balloon pressure should work if you take proper care to run the reaction correctly. The reaction system
needs to be evacuated and filled with hydrogen several times before stirring is started. No matter how you run the reaction vigorous or even "violent"
mixing is required to maximize catalyst exposure to hydrogen. Typical magnetic stirring only works well for small scale reactions in regular
glassware. Using a Morton flask will often give superior results. Your 5%Pd/C should work just fine. If your catalyst is old, it may need to be
"pre-reduced" before adding the substrate.
AvB
|
|
|
nleslie321
Hazard to Self
Posts: 62
Registered: 7-11-2017
Location: krakatoa
Member Is Offline
Mood: just right
|
|
I managed to complete the previous experiment. I am now trying a deprotection of a n-benzyl group attached to a piperidine based compound. I now have
10% Pd/C so should i also try this in an acidic environment?
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
