Synthesis
The general procedure for the synthesis of tert-butyl (S)-2-((methylamino)methyl)pyrrolidine-1-carboxylate from N-methylallylamine and N-BOC-L-prolinol was as follows: Boc-L-prolinol (6.03 g, 30 mmol) was dissolved in anhydrous DCM (120 mL), TEA (15 mL) and anhydrous DMSO (33 mL) were added. Subsequently, PyrSO3 powder (total 30 g) was added in batches of 5 g each for 2 h until the LCMS assay showed complete consumption of raw alcohol. The reaction mixture was washed sequentially with 6N NaHSO4 (3 × 100 mL) and water (2 × 100 mL) and then transferred to a flask. To the flask was added N-methylallylamine (2.8 mL, 29 mmol) followed by NaBH(OAc)3 (6.36 g, 30 mmol). After stirring for 30 min, the mixture was transferred to a partition funnel, the organic layer was washed with water (100 mL), dried and concentrated to give an oily product (4.5 g). This oily product was dissolved in THF (100 mL) and bubbled with N2 gas for 10 minutes. Thiosalicylic acid (4.1 g, 26.6 mmol), Pd2dba3 (137 mg, 0.5 mmol) and 1,4-bis(diphenylphosphino)butane (128 mg, 0.30 mmol) were added. The reaction mixture was sealed and stirred for 1 h at room temperature and then concentrated. It was washed sequentially with 4N NaOH (2 x 50 mL) and water (50 mL), dried and concentrated to give a red oily material. This oily material was stirred with hexane (200 mL) for 10 min, the hexane layer was separated and concentrated to give the target product (3.0 g).MS (M + 1)+: 215.2.
