1. heterogeneous metal catalyst.
1. pd/c is better than pt. because it won't hydrogenate aromatic rings.
2. Benzyl ether and trityl ether can be kept by addition of nitrogen containing base (Py, TEA, ...), the selectivity is very good.
3. Benzyl ether reduced quicker in THF than in MeOH.
3. Ir black gives better facial selectivity than Pd/c, PtO2.
4. hydrogenation in polar solvents is quicker. AcOH>MeOH>EtOH>THF. But facial selectivity is worse.
5. trace of water can activate the metal surface. Good for both hydrogenation and benzyl removal.
2. homogeneous catalysts
wilkinson's catalyst, facial selectivity is bad.
3. hydrazine reduction.
active NH=NH generated by heating tosylhydrazine with base.
very useful when a gental touch is desired.
can reduce triple bond to double bond.
Wednesday, May 14, 2008
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2 comments:
Just found out the other day that you can hydrogenate with Pd/C using triethylsilane as your hydride source. This method works well for enones, enoates, etc. A bit more expensive than using hydrogen, but interesting nevertheless.
P.S. I think my boss would literally explode if he caught me using Wilkinson's to wipe out a double bond.
This remind me another common hydrogen source: formic acid.
about wilkinson's catalyst, I never touch it so really don't know anything about it.
Thank you for your comment.
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