(R)-2-[2-bromo-4-fluoro-6-(prop-1-enyl)phenoxy]but-3-enyl 4-methylbenzenesulfonate → (R)-(8-bromo-6-fluoro-2H-chromen-2-yl)methyl-4-methylbenzenesulfonate

Participants

Reaction Steps

To a solution of (R)-2-[2-bromo-4-fluoro-6-(prop-1-enyl)phenoxy]but-3-enyl 4-methylbenzenesulfonate (7.26 g, 0.016 mol) in dry dichloromethane (300 mL) at room temperature under nitrogen was added benzylidene-bis(tricyclohexylphosphine)-dichlororuthenium (2.6 g, 3.2 mmol) and the reaction mixture stirred at room temperature for 18 hours. The reaction mixture was then concentrated under reduced pressure to a small volume and directly pre-adsorbed onto silica gel. Purification by flash chromatography using a solvent gradient of 5 to 30% ethyl acetate in hexane gave 6.7 g (100%) of (R)-(8-bromo-6-fluoro-2H-chromen-2-yl)methyl-4-methylbenzenesulfonate as a grey solid. [α]D25=+206.6° (c 1% solution in MeOH); MS (ES) m/z 430.0 ([M+NH4]+).

Provenance & Evidence