ASYMMETRIC-SYNTHESIS OF 3-CHLORO-3-FLUORO-2,4-DISUBSTITUTED AND 3-FLUORO-2,4-DISUBSTITUTED TETRAHYDROFURANS BY THE FLUORINATED SULFOXIDE CHIRON ROUTE

An efficient procedure for the preparation of the title compounds in m oderate to high enantiomeric purity has been realized starting from ol efins tethered on the fluoriated sulfinyl chiron 6, prepared from meth yl 4-methylphenyl sulfoxide and ethyl dichlorofluoroacetate. Radical-p romoted cyclization of intermediates 9 according to the tributyltin hy dride method afforded 3-chloro-3-fluorotetrahydrofuran derivatives 12, from which the corresponding 3-fluorotetrahydrofurans 15 were obtaine d by reductive dechlorination. Structural assignments have been done o n the basis of H-1, C-13 and F-19 NMR data and NOE difference experime nts.