C([Li])CCC.[CH3:6][N:7]1[CH2:12][CH:11]=[C:10]([C:13]2[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=2)[CH2:9][CH2:8]1.[CH3:19][C:20]([CH3:22])=[O:21].Cl>O1CCCC1>[C:13]1([C:10]23[CH2:9][CH:8]([O:21][C:20]2([CH3:22])[CH3:19])[N:7]([CH3:6])[CH2:12][CH2:11]3)[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=1n-Butyllithium (15 ml of 1.5M solution in hexane) was added under nitrogen to a solution of 4.7 g of commercially available 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (II: R1 =Me; R2, R3 =H; R4 =phenyl) in 50 mL of tetrahydrofuran, kept at -10°. The deep red solution was stirred at -10° for 15 min and then transferred in a slow stream into a stirred mixture of 15 mL of acetone and 25 mL of tetrahydrofuran and kept at -70°. Excess 10% hydrochloric acid was added after stirring at -70° for 5 min; the mixture was allowed to come to room temperature, and then washed with toluene. The aqueous layer was made basic with sodium hydroxide and extracted with methylene chloride. Removal of the solvent from the dried solution and short-path distillation of the residue (90°-135° bath temperature, 5×10-4 mm Hg [0.07 Pa]) gave 2.79 g of 5-phenyl-2,6,6-trimethyl-7-oxa-2-azabicyclo[3.2.1]octane (III: R1, R5, R6 =Me; R2, R3 =H, R4 =phenyl) as an oil of ca. 85% purity.
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