(Hive Bee)
12-29-02 13:18
No 393795
      CTH: donors and catalysts
(Rated as: excellent)

Here is some information about different donors and catalysts for CTH.


Cyclohexene (Pd)
1,3-Cyclohexadiene (Pd)
1,4-Cyclohexadiene (Pd)
1-Methyloctalin (Pd)
trans-2-Methyloctalin (Pd)
Tetralin (Pd)
1,6-Dimethyltetralin (Pd)
6-Methyltetralin (Pd)
d-Limonene (Pd)
alpha-Pinene (Pd)
beta-Pinene (Pd)
alpha-Phellandrene (Pd)
beta-Phellandrene (Pd)
Terpinolene (Pd)
Cadalene (Pd)
Pulegone (Pd)
Selinene (Pd)
Ethanol (Raney Nickel)
2-Propanol (Raney Nickel)
Methanol (PtCl2(Ph3As)2 + SnCl2*H2O)
Diethylcarbinol (Raney Nickel)
Octanol (RuCl2(Ph3P)3)
Cyclohexanol (Raney Nickel)
Benzylalcohol (RuCl2(Ph3P)3)
alpha-Phenylethanol (RuCl2(Ph3P)3)
beta-Phenylethanol (RuCl2(Ph3P)3)
o-Cyclohexylphenol (Pd)
Formic acid, and its salts (almost all catalysts can be used)
Hypophosphorous acid, and its salts (almost all catalysts can be used)

The donor can, in principle, be any organic compound whose oxidation potential is sufficiently low so that the hydrogen transfer can occur under relatively mild conditions. At higher temperatures, especially in the precense of a catalyst, almost any organic compound can donate hydrogen (catalytic cracking), but this has little potential for controlled synthesis.

Reduction of cinnamic acid with various donors

Reaction conditions: 10%w/w 10%Pd/C, refluxing xylene as solvent, if not the donor acts as solvent. Reaction time refers to quantitative conversion to hydrocinnamic acid, unless otherwise noted.

Donor                   Solvent          Reaction time
p-Menthane               no                  16 hours (only trace reduction)
delta1-p-Menthene    yes                100 minutes
alpha-Phellandrene     yes                  2 minutes
Limonene                  yes                  3 minutes
alpha-Pinene              no                 300 minutes
beta-Pinene               no                 360 minutes
Camphene                 no                 360 minutes (no reaction)
Tetralin                    yes                 60 minutes
Decalin                     no                 360 minutes (only trace reduction)

Ref:Chemical reviews, 1974, vol. 74, No 5. 567-580

Catalytic hydrogenation freak