of phosgene gas the reaction mixture was then stirred at 0 u00b0 c for about 1 hour followed by warming to room temperature at which point tlc analysis ch 2 cl 2 hexane 2 1 showed nearly complete consumption of starting material and formation of a single more polar product the reaction was stirred at room temperature for an additional 2 hours followed by gentle warming to remove excess phosgene the reaction mixture was diluted with ethyl acetate 200 ml and washed with 2n hcl 2 u00d7 100 ml water 1 u00d7 100 ml brine and dried na 2 so 4 concentration of the ethyl acetate extract in vacuo gave a total of 210 mg of dark yellow brown oil which was purified on a silica gel column ch 2 cl 2 affording 0 17 g of light brown foamy solid recrystallization from toluene hexane gave an orange brown crystalline solid m p 208 u00b0 210 u00b0 c comprising a mixture of isomers high resolution mass spectra m 471 0225 calcd for c 23 h 12 o 3 ns 2 f 3 471 0212 ir gkbr 1700 and 1780 cm 1 the procedure of example 1 was repeated but using as reactants the individual isomers identified as isomers a and b of the example 1 starting material the isomer a product melted at 180 u00b0 182 u00b0 c the isomer b product at 219 u00b0 221 u00b0 c in like manner following the procedure of example 1 mutis mutandi the compounds listed below are prepared ______________________________________ str3 x r sup 1 r sup 2______________________________________h ch sub 3 ch sub 3h 2 thienyl phenyl5 cf sub 3 2 thienyl.