Pyridine → (+)-(S,R)-6-Fluoro-3,4-dihydro-2-(2-oxiranyl)-2H-1-benzopyran

Participants

Reaction Conditions

Reaction Steps

(R)-1-((S)-6-fluoro-3,4-dihydro-2H-chromen-2-yl)ethane-1,2-diol (0.27 g, 1.27 mmol) was dissolved in dichloromethane (10 ml) under nitrogen atmosphere and pyridine (510 μl) added under stirring. The reaction mixture was then cooled to 1° C. and tosyl chloride (0.24 g, 1.27 mmol) in dichloromethane (3 ml) was added over a period of 2.5 h. The reaction was quenched with saturated ammonium chloride (1 ml) and further diluted with dichloromethane (10 ml) and demi water (10 ml). The aqueous layer was separated and further extracted with dichloromethane (15 ml). The collected organic layers were dried over magnesium sulfate, filtered and concentrated in vacuo to furnish a colourless oil. Said oil was dissolved in methanol (3 ml) and dichloromethane (6 ml) under stirring in nitrogen atmosphere and potassium carbonate (0.32 g, 2.35 mmol) added. The reaction mixture was left to stir for 15 h at 25° C. The reaction was then diluted with water (10 ml) and dichloromethane (10 ml). The separated aqueous layer was further extracted with dichloromethane (20 ml). The collected organic layers were dried over magnesium sulfate and concentrated in vacuo to furnish crude (S)-6-fluoro-3,4-dihydro-2-((R)-oxiran-2-yl)-2H-chromene as a yellow oil. Separation via chomatography on silica, using heptane:ethyl acetate 9:1 as eluent, furnished 30 mg of (S)-6-fluoro-3,4-dihydro-2-((R)-oxiran-2-yl)-2H-chromene as a colourless oil (12% yield).

Provenance & Evidence