Reaction Steps
A reaction vial equipped with septa cap fitted with nitrogen inlet needle was charged with palladium(II) acetate (0.029 g, 0.128 mmol), cesium carbonate (1.460 g, 4.48 mmol) and Xantphos (0.111 g, 0.192 mmol). The vial was purged with nitrogen and 1,4-dioxane (8.7 mL) was added. The suspension was allowed to stir at about rt for about 10 min then TEA (0.027 ml, 0.192 mmol) was added dropwise. The mixture was stirred at rt for about 10 min and heated to about 80° C. for about 10 min. To the mixture was added a solution of rac-(4aR,11bS)-11b-ethyl-1,2,4,4a,5,6,7,11b-octahydrospiro[dibenzo[a,c][7]annulene-3,2′-[1,3]dioxolan]-9-yl trifluoromethanesulfonate (20, R2=Ethyl) (1.391 g, 3.20 mmol) and benzophenone imine (0.645 ml, 3.84 mmol) in Dioxane (4 mL). The mixture was heated at about 100° C. for about 3 h. The reaction was allowed to cool to rt and partitioned between EtOAc (50 mL) and water (50 mL). The layers were separated and the organic layer was washed with brine (50 mL) and then filtered through a pad of Celite®. The filter pad was washed with a 9:1 mixture of DCM/MeOH (50 mL) then the filtrate was concentrated under reduced pressure to give a solid on standing. The material was triturated with three portions of EtOAc (5 mL, then 2×2 mL) to give a yellow solid. The EtOAc supenatants were combined and concentrated under reduced pressure. The residue was triturated with Et2O (10 mL) then the solid was collected by filtration. The solids from both triturations were combined and dried under vacuum to yield rac-(4aR,11bS)—N-(diphenylmethylene)-11b-ethyl-1,2,4,4a,5,6,7,11b-octahydrospiro[dibenzo[a,c][7]annulene-3,2′-[1,3]-dioxolan]-9-amine (21, R2=Ethyl) (1.205 g, 81%); LC/MS, method 3, Rt=3.53 min, MS m/z 466 (M+H)+. 1H NMR (400 MHz, CDCl3) δ 7.77 (d, J=7.6 Hz, 2H), 7.53-7.37 (m, 3H), 7.33-7.20 (m, 3H), 7.10 (d, J=7.2 Hz, 2H), 6.96 (d, J=8.4 Hz, 1H), 6.50 (bs, 2H), 3.98-3.84 (m, 4H), 2.86-2.79 (m, 1H), 2.54-2.48 (m, 1H), 2.38-2.32 (m, 1H), 2.27-2.12 (m, 1H), 2.10-2.01 (m, 2H), 1.90-1.72 (m, 1H), 1.68-1.52 (m, 4H), 1.51-1.40 (m, 2H), 1.39-1.23 (m, 2H), 0.57 (t, J=7.4 Hz, 3H).
