A solution of tert-butyl 6-bromo-2-methyl-spiro[3,4-dihydropyrrolo[1,2-a]pyrazine-1,4′-piperidine]-1′-carboxylate (2 g, 5.2 mmol) and N-cyclohexyl-N-methyl-cyclohexanamine (1.67 mL, 7.81 mmol) in 1,4-dioxane (8.0 mL) was purged with N2 for 5 minutes. 1-Vinyloxybutane (7.04 mL, 52.04 mmol), Pd(dba)3 (1.078 g, 1.04 mmol) and tri tert-butylphosphane (642.0 μL, 2.60 mmol) were added and the reaction was heated at 80° C. for 5 hours in a pressure vessel. The reaction was filtered through a plug of celite using ethyl acetate. The solvent was evaporated under reduced pressure. The crude product was purified by silica gel chromatography utilizing a gradient of 1-100% ethyl acetate in hexane to yield tert-butyl 6-acetyl-2-methyl-spiro[3,4-dihydropyrrolo[1,2-a]pyrazine-1,4′-piperidine]-1′-carboxylate (672.1 mg, 1.93 mmol, 37%) as a yellow solid. 1H NMR (400 MHz, DMSO) δ 7.04 (d, J=4.1 Hz, 1H), 6.12 (d, J=4.2 Hz, 1H), 4.17 (t, J=6.0 Hz, 2H), 3.83-3.68 (m, 2H), 3.21 (t, J=6.0 Hz, 2H), 3.17-2.91 (m, 2H), 2.31 (s, 3H), 2.24 (s, 3H), 2.07-1.97 (m, 2H), 1.72-1.59 (m, 2H), 1.41 (s, 9H). ESI-MS m/z calc. 347.2, found 348.5 (M+1)+; Retention time: 0.95 minutes (3 minute run).
