Scope of the hydrogenation reaction

All these hydrogenation reactions are quantitative, easy to perform on a large scale, and thus represent an highly convenient approach to a number of optically pure compounds. In most cases, it compares favourably with 

7 SYNTHESIS OF A CYLINDRICALLY CHIRAL DIPHOSPHINE AND ASYMMETRIC HYDROGENATION OF DEHYDRO AMINO ACIDS 

Department of Chemistry, Sogang University, Seoul 121-742, Korea 

In a degassed 250 mL round-bottomed flask equipped with a magnetic stirring bar were placed l,l -ferrocenedicarboxaldehyde (8.30 g), (lR,2S)-l-phenyl-2-(l-piperidinyl)propane-l -thiol (400 mg) and dry diethyl ether (115mL). Diethylzinc in toluene (1.1 M, 28.7 mL) was added dropwise to the mixture at 0 °C. The reaction mixture was stirred at 0 °C for 10 hours. 

After the period, the reaction was quenched by adding a solution of 1 M HC1 with vigorous stirring at 0 °C until no more ethane gas was generated. The white inorganic material was removed by filtration over a glass filter. 

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