Reaction Steps
A mixture of 1-(3-fluorophenyl)-2,2,5,5-tetramethyl-1-aza-2,5-disilacyclopentane (14.56 g, 57.4 mmol) in dry tetrahydrofuran (230 mL) at −78° under nitrogen is treated with sec-butyllithium (1.3 M in cyclohexane, 48.6 mL, 63.1 mmol) dropwise over 5 mins, and the resulting mixture is stirred at -780 for 2 hrs. The mixture is then treated with a solution of tetrahydrothiopyran-4-one (7.00 g, 60.3 mmol) in dry tetrahydrofuran (60 mL) dropwise over 10 mins and is stirred for 3.5 hrs, during which the reaction temperature is allowed to rise to 0°. The mixture is quenched with saturated aqueous ammonium chloride (100 mL), diluted with water (100 mL), the layers are separated, the aqueous phase is extracted with ether (100 mL), and the combined organic phase is washed with saline (100 mL), dried over anhydrous sodium sulfate and concentrated under reduced pressure. The residue is then dissolved in methanol (230 mL) and treated with anhydrous potassium carbonate (15.9 g, 115 mmol), and the mixture is stirred at 20-25° for 1 hr, concentrated under reduced pressure, diluted with ether (150 mL) and water (150 mL), the layers are separated, the aqueous phase is extracted with ether (100 mL), and the combined organic phase is washed with water (50 mL) and saline (50 mL), dried over anhydrous magnesium sulfate and concentrated under reduced pressure to give the crude 3-fluoro-4-[4-(hydroxy)tetrahydrothiopyran-4-yl]benzenamine intermediate (Rf=0.09 by TLC, ethyl acetate/hexane (25/75)). A mixture of this intermediate and sodium bicarbonate (9.54 g, 115 mmol) in tetrahydrofuran (230 mL) and water (100 mL) is treated with benzyl chloroformate (8.2 mL, 57.4 mmol) with vigorous stirring, and the resulting mixture is stirred at 20-25° for 2 hrs. The mixture is then washed with water (2×50 mL) and saline (50 mL), dried over anhydrous sodium sulfate and concentrated under reduced pressure, the residue is then chromatographed on silica gel (230 -400 mesh, 350 g), eluting with methanol/methylene chloride (0.5/99.5), and those fractions with an Rf=0.15 by TLC (ethyl acetate/hexane, 25/75) are pooled, concentrated and recrystallized from ethyl acetate/hexane to give the title compound, mp=133-134°; NMR (400 MHz, CDCl3) 7.37, 7.00, 6.70, 5.21, 3.23, 2.45, 2.38, 2.05 and 1.92 δ; CMR (100 MHz, CDCl3) 160.5, 153.5, 138.8, 136.1, 130.5, 129.0, 128.9, 128.7, 127.0, 114.3, 107.4, 71.6, 67.7, 37.9 and 24.2; IR (mull) 3467, 3317, 1708, 1605, 1538, 1412, 1313, 1251, 1241, 1233, 1223, 1066, 855, 742, 695 cm−1; MS (EI) m/z (rel. intensity) 361 (M+, 11), 334 (4), 333 (19), 301 (5), 300 (29), 256 (4), 228 (3), 92 (8), 91 (99), 65 (6); HRMS (EI) calculatea for C19H20FNO3S =361.1148, found=361.1153.
