Experimental Procedure
Synthesis of Ni(II) catalyst, NiCl2(PPh3)2
Dissolve NiCl2.6H2O (2.5g) in ethanol (30 ml) in a round bottomed flask equipped with a magnetic
stirring bar. Add a solution of triphenylphosphine (5.0g) in hot ethanol (40 ml) was dropwise by
pipette to the stirring NiCl2.6H2O solution. After the addition, fit the flask with a reflux condenser
and heat the mixture under reflux for 1 hour. Allow the solution to cool to room temperature and
collect the product by filtration. Wash the crystals with a little ether, and dry them in a dessicator.
Record the yield and m.pt. of your product.
Hydrogenation of ketones
Carry out your reduction using 2g of the ketone you have been assigned. Calculate the amount of
catalyst that you will need - you should use 0.15 mol equivalents of catalyst to ketone.
Place your ketone in a flask with a stir bar and add iso-propanol (propan-2-ol, 70 ml). To this add
your pre-weighed amount of catalyst, and powdered sodium hydroxide (0.16g). Heat the mixture
under a gentle reflux, following the reaction by tlc (visualise with UV light or in an iodine tank).
When the reaction is complete (may take overnight or longer) allow the mixture to cool to room
temperature and remove the iso-propanol using a rotary evaporator. To the remaining residues add
ether (50 ml) and then were filter the mixture through a short pad of silica to remove the catalyst.
Evaporation of the ether leaves the crude product. Purify your product either by recrystallisation
(4-tert-butycyclohexanol and diphenylmethanol) or vacuum distillation using a water pump vacuum
and a B10 distillation set (1-phenylethanol). In the case of the recrystallisation, you may see very
quick precipitation of a solid from the solvent - this is usually triphenylphosphine and should be
removed by hot filtration. Further cooling induces crystallisation of the product.
Record the IR and nmr spectra of your products, as well as the m.pt. or b.pt. as appropriate.
Write up
The write up should conform to a J. Chem. Soc., Perkin Trans. I, style (Title, Abstract,
Introduction, Results and Discussion, Experimental, References). Your introduction must include
discussion of the following points:
a)a proposed mechanism for the reaction
b)three recent (post-1993) synthetic applications of transfer hydrogenation (from any hydride
source you choose). Examples of asymmetric applications are encouraged!
References and Notes
1."Hydrogenation Methods", P. N. Ryland, Academic Press, London, 1985
2.J. F. Young, J. A. Osborn, F. H. Jardine, G. Wilkinson, J. Chem. Soc.,Chem.
Commun., 1965, 131
3.B. D. Vineyard, W. S. Knowles, M. J. Sabacky, G. L. Bachman, D. J. Weinkauff, J.
Am. Chem. Soc., 1977, 99, 5946
4.S. Iyer, J. P. Varghese, J. Chem. Soc., Chem. Commun., 1995, 465
Steve Marsden, 28/9/98
