3-Bromopyridine → 1-(2-Chloro-9,10-dihydro-9,10-methanoanthracen-9-ylmethyl)-4-(3-pyridyl)piperidin-4-ol

Participants

Reaction Conditions

Reaction Steps

To a cooled solution (-90° C.) of n-butyllithium (2.5M in hexane, 2.40 mL, 6.0 mmol, 1.5 eq) in tetrahydrofuran (40 mL) under nitrogen was added freshly distilled 3-bromopyridine (0.540 mL, 5.6 mmol, 1.4 eq). The metal-halogen exchange reaction was warmed to -75° C. and maintained for 1.5 h. During that time a dark green solution evolved with the appearance of fine particulate. A solution of 1-(2-chloro-9,10-dihydro-9,10-methanoanthracen-9-ylmethyl)-4-piperidinone (1.35 g, 4.0 mmol) in tetrahydrofuran (10 mL) was then added dropwise with considerable lightening of the solution color to a deep yellow. The reaction was warmed to room temperature over 1 h and quenched with water (50 mL). The aqueous phase was extracted with ethyl acetate (3×60 mL). Combined organic extracts were dried over anhydrous magnesium sulfate, filtered, and reduced to an oil. The reaction mixture was purified by flash chromatography over silica gel (80 mL, eluent: ethyl acetate) to yield 1.35 g (81%) of the title compound as a white solid. TLC analysis (Rf 0.20, ethyl acetate). 1H NMR (D6 -DMSO, 300 MHz) 8.69 (br s, 1H), 8.41 (d, J=4.5 Hz, 1H), 7.83 (dt, J=8.0 Hz, 1H), 7.29 (m, 5H), 6.95 (m, 3H), 5.05 (s, 1H), 4.35 (s, 1H), 3.41 (m, 2H), 3.34 (s, 1H), 2.75 (m, 4H), 1.92 (m, 2H), 1.62 (m, 2H) MS (CI, CH4) m/z 417 (M+1,100), 419 (36), 445 (M+29,15), 399 (15) The free base was dissolved in diethyl ether containing a small amount of methylene chloride, acidified with ethereal HCl, and the hydrochloride salt suspension was diluted with additional ether. The salt was filtered, washed with fresh ether and dried in vacuo (50° C., 13 pascal, 18 h) to yield a white solid, mp 225°-228° C. (dec).

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