example 44b from u00b1 cis n acetyl 1 1a 2 7b tetrahydro cyclopropa c quinoline 1 carboxylic acid ethyl ester 2 0 mg 7 7 mmol commercially available 2 5 difluorophenol 20 g 0 15 mol k 2 co 3 53 g 0 38 mol and commercially available 3 bromopropyne 45 g 0 38 mol were dissolved in acetone 300 ml refluxed over night cooled and filtrated the solvent was removed and the crude product dissolved in ether and washed with water and brine the organic phase was evaporated and the crude product was re dissolved in a small amount of ether and filtrated through a column of basic al 2 o 3 evaporation and drying gave 20 g 80 of 2 4 difluoro 2 prop ynyloxy benzene b 2 4 difluoro 2 propynyloxybenzene 20 g 0 12 mol was dissolved in n n diethyl aniline 100 ml and heated under argon atmosphere at 225 deg celcius with an oil bath for 6 8 h ether 150 ml was added and the aniline was removed by extraction using 2 hcl aq purification by chromatography silica gel n hexane gave 5 8 difluoro 2h chromene 5 8 g 29 5 8 difluoro 2h chromene 5 g 0 03 mol rh ii ac 2 2 0 39 g 0 00089 mol was dissolved in 1 2 dichloroethane 60 ml or ethanol free chloroform ethyl diazoacetate 9 4 ml 0089 mol in the same solvent was added dropwise over a period of approximately 5 h under n 2 atmosphere the solvent was then removed under vacuum and the mixture was taken upp in ethyl acetate washed with nahco 3 aq water.