a 5 0 g 20 mmole in dichloromethane was stirred at 0 u00b0 aqueous solutions of sodium dihydrogen phosphate 0 1 m 25 ml and sodium monohydrogen phosphate 0 1 m 100 ml were added followed by m chloroperoxybenzoic acid 80 85 4 42 g 22 mmole the mixture was stirred rapidly for 30 minutes at which time additional m chloroperoxybenzoic acid 1 62 g 8 mmole was added stirring was continued at 0 for 4 hours then the mixture was diluted with additional dichloromethane washed sequentially with 10 w v aqueous sodium thiosulfate saturated aqueous sodium becarbonate and water and then dried mgso 4 and concentrated under reduced pressure the residual oil 5 4 g consisting largely of 2 2 bis 4 fluorophenyl 3 ethyloxirane was used without further purification nmr cdcl 3 7 30 4h m 7 06 4h m 3 32 1h t j 5 hz 1 38 2h m 1 00 3 h t j 6 hz mass spec ci m z 261 33 123 100 part c a solution of the product from part b 5 0 g 19 2 mmole in dmf 55 ml was stirred at room temperature 18 crown 6 0 49 g 1 9 mmole and potassium imidazole 5 11 g 48 mole were added the mixture was stirred at 90 u00b0 for 20 hours then cooled and diluted with a 1 1 mixture of ether and ethyl acetate 500 ml the solution was washed with water then with brine dried mgso 4 and concentrated under reduced pressure the residual solid was triturated with ether and collected by filtration to provide the title compound 5 15 g 82 as a.