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