6-fluoro-2-methyl-2,3-dihydrochromen-4-one

Conditions: temp:120.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 11.2 G (0.1 mol) of para-fluorophenol and 17.2 g (0.2 mol) of crotonic acid were dissolved in 100 ml of polyphosphoric acid, and the solution was reacted with vigorously stirring at 120° C. for 8 hours. After cooling, the reaction solution was poured into 450 ml of iced 2N-sodium hydroxide solution, and the mixture was extracted with 500 ml of chloroform. The chloroform layer was washed with 2N-sodium hydroxide solution and with water, followed by drying over magnesium sulfate. The solvent was distilled off, and the residue was recrystallized from n-hexane in the amount of about ten times. There were thus obtained 5.8 g (yield : 32%) of the subject material, 6-fluoro-2-methyl-4- chromanone. the solution was reacted After cooling the mixture was extracted with 500 ml of chloroform The chloroform layer was washed with 2N-sodium hydroxide solution and with water by drying over magnesium sulfate The solvent was distilled off the residue was recrystallized from n-hexane in the amount of about ten times

Conditions: temp:92.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 56.1 g (0.5 mol) 4-fluorophenol, 172 g (2 mol) crotonic acid and 1120 ml methane sulfonic acid was heated at 92° C. for 20 hours. The reaction was cooled to 0° C., poured onto 2 liters ice and 2 liters water and extracted with 3×800 ml diethyl ether. The combined organic layers were washed with 3×500 ml water, 4×500 ml 1N sodium hydroxide, 2×500 ml water and 500 ml brine, dried over magnesium sulfate and concentrated in vacuo to give 48.5 g crude solid. The latter was purified by flash chromatography on 1000 cc silica gel using diethyl ether:hexane (1:10) as eluant. The title compound was obtained as a yellow solid, 37 g (41%); m.p. 65°-68° C. The Chemical Abstracts Registry Nos. for this compound are 88754-96-5 and 82320-16-9. The reaction was cooled to 0° C. extracted with 3×800 ml diethyl ether The combined organic layers were washed with 3×500 ml water, 4×500 ml 1N sodium hydroxide, 2×500 ml water and 500 ml brine dried over magnesium sulfate concentrated in vacuo to give 48.5 g crude solid The latter was purified by flash chromatography on 1000 cc silica gel

Conditions: temp:120.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 11.2 G (0.1 mol) of para-fluorophenol and 17.2 g (0.2 mol) of crotonic acid were dissolved in 100 ml of polyphosphoric acid, and the solution was reacted with vigorously stirring at 120° C. for 8 hours. After cooling, the reaction solution was poured into 450 ml of iced 2N-sodium hydroxide solution, and the mixture was extracted with 500 ml of chloroform. The chloroform layer was washed with 2N-sodium hydroxide solution and with water, followed by drying over magnesium sulfate. The solvent was distilled off, and the residue was recrystallized from n-hexane in the amount of about ten times. There were thus obtained 5.8 g (yield : 32%) of the subject material, 6-fluoro-2-methyl-4- chromanone. the solution was reacted After cooling the mixture was extracted with 500 ml of chloroform The chloroform layer was washed with 2N-sodium hydroxide solution and with water by drying over magnesium sulfate The solvent was distilled off the residue was recrystallized from n-hexane in the amount of about ten times