Reaction Steps
A mixture of rac-(4aR,11bS)-10-bromo-11b-ethyl-1,2,4,4a,5,6,7,11b-octahydrospiro[dibenzo[a,c][7]annulene-3,2′-[1,3]dioxolan]-9-amine (23, R2=Ethyl) (0.255 g, 0.670 mmol) in DME (6 mL) and water (2 mL) was degassed by bubbling nitrogen through the mixture for about 15 min. Cesium carbonate (0.655 g, 2.011 mmol), 2,4,6-trimethyl-1,3,5,2,4,6-trioxatriborinane (0.168 g, 1.341 mmol) and PdCl2(PPh3)2 (0.024 g, 0.034 mmol) were added and the mixture was heated to about 90° C. for about 22 h. The mixture was cooled to rt, diluted with EtOAc (25 mL) and washed with sat. aq. NaHCO3 (10 mL). The organic layer was dried over MgSO4, filtered and concentrated under reduced pressure. The residue was purified on silica gel (4 g) using a gradient of 0-15% EtOAc in DCM. Product fractions were combined and concentrated under reduced pressure to yield rac-(4aR,11bS)-11b-ethyl-10-methyl-1,2,4,4a,5,6,7,11b-octahydrospiro[dibenzo[a,c][7]annulene-3,2′-[1,3]dioxolan]-9-amine (24, R2=Ethyl) (0.112 g, 53%); LC/MS, method 3, Rt=2.53 min, MS m/z 316 (M+H)+. 1H NMR (400 MHz, DMSO) δ 6.72 (s, 1H), 6.35 (s, 1H), 4.61 (s, 2H), 3.88-3.70 (m, 4H), 2.79-2.72 (m, 1H), 2.54-2.47 (m, 1H), 2.33-2.27 (m, 1H), 2.13-2.04 (m, 1H), 2.00 (s, 3H), 1.97-1.88 (m, 2H), 1.72-1.57 (m, 3H), 1.53-1.46 (m, 1H), 1.41-1.14 (m, 5H), 0.59 (t, J=7.4 Hz, 3H).
