7-bromo-3-chloro-1-fluoro-5H-chromeno[2,3-c]pyridin-5-one → 7-bromo-3-chloro-1-fluoro-5-methylene-5H-chromeno[2,3-c]pyridine

Participants

Reaction Steps

To a solution of 7-bromo-3-chloro-1-fluoro-5H-chromeno[2,3-c]pyridin-5-one (50 mg, 0.152 mmol) in 5 mL of dry THF at −78 C was added methylmagnesium chloride, 3.0 m solution in tetrahydrofuran (16.87 μL, 0.228 mmol) (0.07 mL) and the reaction was slowly warmed up to −30 C. Only half of conversion was detected. To this was added another batch of methylmagnesium chloride, 3.0 m solution in THF (16.87 μL, 0.228 mmol) (0.07 mL). The reaction was quenched at −30 C with sat. NH4Cl, extracted with EA, dried over Na2SO4, filtered and evaporated to dryness. It was then treated with 1 mg of PPTS in DCM at 25 C for 0.5 h. After cooling, 0.1 g of NaHCO3 was added the solvent was evaporated to dryness to give crude 7-bromo-3-chloro-1-fluoro-5-methylene-5H-chromeno[2,3-c]pyridine which was directly used in the next step.

Provenance & Evidence