Appendix Eleven
While reduction of the olefins (main section g) can be carried out with hydrogen gas, this is not very convenient. Hydrazine hydrate can be used, while the following procedure allows the use of cyclohexene and should give excellent results.
The reduction is best carried out in vigorously refluxing tetrahydrofuran as solvent; apparently the mechanical effect of boiling aids in detaching hydrogen from the catalyst surface. The catalyst employed must be palladium, other catalysts such as platinum or Raney Nickel are not satisfactory. At least 8 two-molar excess of cyclohexene is used, but more will do no harm and in a few cases has given better results. Commercial palladium black, or palladium deposited on charcoal, calcium carbonate, or alumina is equally effective so there is no need in this case to prepare the specially active catalyst of Appendix Five. After use the filtered catalyst can be washed and used for later reactions. Eventually the catalyst becomes ineffective through poisoning and the number of operations in which it can be used successfully must be established by trial.
Example: Fifty grams of the olefin to be reduced (from (f), approximately one-fifth mole), are added to a flask containing one gram of commercial palladium-on-charcoal, 50 grams cyclohexene (about one-half mole), and 300 ml. tetrahydrofuran. The flask is fitted with water-cooled reflux condenser and heated at vigorous boil for 15 hours to four days (the time required must be established by experiment). At the end of this time the reaction mixture is allowed to cool, the catalyst filtered out, and the product 3,5-dimethoxy-(alkyl)-benzene isolated by fractional distillation. (Reference 418, See also (Reference 389) which 'was not available when this was written)
Appendix Ten
Appendix Twelve