Dihydro-3(2H)-thiophenone → 3-Fluoro-4-[3-(hydroxy)tetrahydrothiophen-3-yl]benzenamine

Participants

Reaction Conditions

Reaction Steps

A solution of 1-(3-fluorophenyl)-2,2,5 ,5-tetramethyl-1-aza-2,5-disilacyclopentane (EXAMPLE 20, Step 1, 1.00 g) in dry tetrahydrofuran (16 mL) at -78° C. under N2 is treated with sec-butyllithium (1.3 M in cyclohexane, 3.30 mL) dropwise over 2 mins, and the resulting mixture is stirred at -78° C. for 2 hrs. The mixture is then treated with a solution of tetrahydrothiophen-3-one (423 mg) in dry tetrahydrofuran (4.1 mL) dropwise over 2 mins and is stirred at -78° C, allowing the cooling bath to expire over 4 hrs. The mixture is then quenched with saturated aqueous ammonium chloride (25 mL), diluted with water (25 mL), the layers are separated, and the combined organic phase is washed with saline (20 mL), dried over anhydrous sodium sulfate and concentrated under reduced pressure. The residue is dissolved in methanol (16 mL) and treated with anhydrous potassium carbonate (1.09 g), and the mixture is stirred at ambient temperature for 30 mins, concentrated under reduced pressure, diluted with water (20 mL) and extracted with diethyl ether (2×20 mL). The combined organic phase is washed with saline (10 mL), dried over anhydrous magnesium sulfate and concentrated under reduced pressure to give the crude 3-fluoro-4-[3-(hydroxy)tetrahydrothiophen-3-yl]benzenamine intermediate (Rf =0.37 by TLC, ethlyl acetate/hexane (50/50)). A solution of this intermediate in tetrahydrofuran (16 mL) and water (8 mL) is then treated with sodium bicarbonate (662 mg) and benzyl chloroformate (0.56 mL), and the resulting mixture is stirred at ambient temperature for 4 hrs, diluted with water (8 mL), the layers are separated, and the organic phase is washed with saline (10 mL), dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The residue is chromatographed on silica gel (230-400 mesh, 150 g), eluting with ethyl acetate/hexane (25/75), and those fractions with an Rf =0.19 by TLC (ethyl acetate/hexane, 25/75) are pooled and concentrated to give the title compound, mp 134-135° C.

Provenance & Evidence