(±)-3-benzyl 7-tert-butyl 3,7-diaza-bicyclo[4.1.0]heptane-3,7-dicarboxylate (62 mg, 0.187 mmol), CuI (8 mg, 0.2 equiv), and a stirring bar were put in a 100-mL flask. The flask was evacuated and backfilled with N2 gas (3×). Dry THF (5 mL) was added and the mixture was cooled to −40° C. (Cyclobutylmethyl)magnesium bromide in THF (620 μL, 3 equiv., ˜0.89 M) was added slowly. After 8 min, the reaction mixture was allowed to warm slowly to rt. After 20 min, the reaction mixture turned black. After stirring a further 2 h the reaction was complete. Satd aq NH4Cl solution (5 mL) was added to quench the reaction. The reaction mixture was partitioned between EtOAc (50 mL) and satd aq NH4Cl solution (20 mL). The aqueous layer was extracted with EtOAc (20 mL). The combined EtOAc layers were washed with water (15 mL), brine (15 mL), and dried over Na2SO4. After concentration, the residue was purified by Gilson to afford (±)-trans-benzyl 3-(tert-butoxycarbonylamino)-4-(cyclobutylmethyl)piperidine-1-carboxylate (14 mg, 19% yield). MS ESI +ve m/z 425 (M+Na).
