Hydrochloric Acid → 6-fluoro-4-cyano-2H-benzopyran

Participants

Reaction Steps

To a solution of 32 g (0.12 mole) of the crude 6-fluoro-2,3-dihydro-4-cyano-4-[(trimethylsilyl)oxy-]4H-benzopyran in 170 ml of dry pyridine was added 60 ml (0.6 mole) of phosphorous oxychloride. The reaction was heated to reflux for 5 hours then cooled to room temperature. The resulting solution was added dropwise to a solution of 300 cc of concentrated HCl in 1 L of water. This aqueous layer was extracted with EtOAc and the EtOAc layer was dried over Na2SO4, filtered and evaporated to give 16.1 g of product m.p. 114°-115° C. NMR (CDCl3) ppm (delta) 5.00 (d, 2H, J=4 Hz), 6.6-7.3 (m, 4H).

Provenance & Evidence