Chicken (Newbee)
09-25-02 13:06
No 360475
      Wilkinson Catalyst Reductions  Bookmark   

Could a Wilkinson's catalyst Tris(triphenylphosphin)rhodium(I)chloride: ClRh(PPh3)3, be utilized in the presence of ammonium formate and a microwave used to reduce the hydroxy group away from a benzylalcohol?  Could this be carried out in a GAA solvent?  I have been doing some reading on this and it seems like an excellent route for CTH in the microwave, much more suited to the proceedure then classic catalysts.  The ammonium formate addition allows the reaction to occur without the pressure associated with most hydrogen catalyst reactions.  It seems that Alumina or polymer supported formate would be adventageous for this operation also.

As I read more I think skip the microwave and maybe just add heat.  Maybe a little shaking, a 1-2atm H2 gas.  Using the WC maybe it is more possible to skip the chloro intermediated, because of the WC's selective nature.  Seem their is literature supporting this for a ketone reduction.

Any ideas?

(http://fachschaft.cup.uni-muenchen.de/~schleifi/reaktion/reaction/wilkikat.html)
Wilkinson Catalyst Description
 
 
 
 
    Rhodium
(Chief Bee)
09-25-02 14:43
No 360495
      Deoxygenation of benzyl alcohols  Bookmark   

I think that you might need more vigorous rxn conditions for deoxygenation of benzyl alcohols to hydrocarbons. Do you have any references for deoxygenations using Wilkinson?

2-propanol is also a good hydrogen donor for CTH, btw.

Use this search engine: http://www.scirus.com/
 
 
 
 
    Chicken
(Newbee)
09-25-02 15:15
No 360504
      Ref  Bookmark   

"New Rhodium-Catalyzed Allylic Substitution Reactions: Mechanistic Insight and Synthetic Applications"
P. Andrew Evans (Indiana University).

Professor Evans demonstrated that Wilkinsonís catalyst, [Rh(PPh3)3Cl], may be modified in situ to furnish a catalytically active species that facilitates the regioselective allylic substitution of acyclic unsymmetrical chiral non-racemic allylic alcohol derivatives with retention of absolute configuration. In general, allylic carbonate 8 reacts with various nucleophiles to afford the secondary allyl derivatives 9 in high yield and with retention of absolute configuration, along with a small amount of olefin 10 (Scheme 3). A mechanism in which the reaction proceeds with overall retention of absolute configuration via the intermediacy of an enyl (s + p) organorhodium intermediate was proposed.

http://www.albmolecular.com/features/tekreps/vol06/no26/
For the rest.  . .
 
 
 
 
    Rhodium
(Chief Bee)
09-25-02 16:24
No 360533
      That is not a benzylic alcohol dehydrogenation.  Bookmark   

That is not a benzylic alcohol dehydrogenation.
 
 
 
 
    Chicken
(Newbee)
09-26-02 15:11
No 360942
      Here is something similar using a Ni catalyst  Bookmark   

Gross, B.H. / Mebane, R.C. / Armstrong, D.L., Applied Catalysis A: General, Oct 2001
Raney nickel in refluxing 2-propanol is an effective catalytic system for cleaving CO bonds in aromatic alcohols by transfer hydrogenolysis. Deoxygenation of alcohols substituted at the Š-, ‚-, „-, š-, and -positions was...

Edit: This has been posted in Post 393077 (Rhodium: "(pseudo)Ephedrine to Meth w/ Raney-Nickel", Stimulants)
 
 
 
 
    Rhodium
(Chief Bee)
09-26-02 17:15
No 360984
      That's exactly what you want.  Bookmark   

That's exactly what you want.
 
 
 
 
    Chicken
(Hive Bee)
09-26-02 17:49
No 361000
      Raney cobalt  Bookmark   

Seems after further examination that Raney cobalt in refluxing 2-propanol would be the ideal catalyst for use for reduction of epedrine hcl diectly without intermediates to methamphetamine.  Does anyone have experience with Raney Cobalt?  Is it possibe to make Raney Cobalt or is it best purchased?  Raney Ni seems to come in second place, but is less selective, and thus may require the chloro intermediate to be produced for the reaction to work with decent yeilds.  These cobalt and nickle catalysts are not watched correct?  Additionally these sponge catalysts do not require a prereduction like Pd catalysts do.  This seems ideal.