tert-butyl (2S)-piperazine-2-carboxylate

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The crude tert-butyl (S)-piperazine-2-carboxylate from Example 7 was stirred in 2.9 g of water and 2.1 g (18.4 mmol) of 32 percent hydrochloric acid for 20 minutes at 100° C. The mixture was cooled to 0° C. and stirred for a further 1 hour. The hydrochloride which had precipitated out was filtered off and washed with 10 ml of dichloromethane. The yield of the title compound was 0.24 g (41 percent, based on tert-butyl pyrazinecarboxylate). The ee value was 77.6 percent. The hydrochloride which had precipitated out was filtered off washed with 10 ml of dichloromethane

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Analogously to Example 4, 0.52 g (2.85 mmol) of tert-butyl pyrazinecarboxylate (prepared according to Example 2), 25.3 mg (54 μmol) of bicyclo[2.2.1 ]hepta-2,5-dienerhodium(I) chloride dimer and 61.5 mg (113.3 μmol) of 1-[1(R)-(di-tert-butylphosphino)ethyl]-2(S)- (diphenylphosphino)ferrocene were hydrogenated for 20 hours in 10 ml of methanol at 70° C. and 50 bar. A conversion of 67 percent was determined by NMR. The ee value was determined by hydrolyzing the ester (see Example 8).