Olefin Inversion. 3. Preparations and Reductions of vic-Halohydrin Trifluoroacetates

Article abstract of DOI:10.1021/jo01289a030

Treatment of alkenes with N-bromo- and N-chlorosuccinimide in trifluoroacetic acid resulted in stereospecific anti addition of the elements of trifluoroacetyl hypobromite and hypochlorite, respectively.Heating the vic-bromo- or -chlorohydrin trifluoroacetates with NaI in DMF produced olefins with inversion of geometry.Treatment of the adducts with Zn in DMF reduced them to olefins with retention of geometry.Reductive transformations involving the chlorohydrin trifluoroacetates were virtually stereospecific, whereas those involving the bromohydrin trifluoroacetates were >90percent stereoselective for NaI reductions and only 60-90percent stereoselective for reductions by Zn.