Aryl epoxide–halohydrin transformations: stereochemistry of reactions of aryl epoxides with lithium halide–acetic acid reagent

The reactions of indene oxide (4a), 5-methoxyindene oxide (4b), 1,2,3,4-tetrahydronaphthalene-1,2-epoxide (5a) and 6-methoxy-1,2,3,4-tetrahydronaphthalene-1,2-epoxide (5b) with lithium halides in the presence of acetic acid (LiX/HOAc) yield mixtures of cis and trans halohydrins. These results are in contrast to those reported for the reactions of a series of aliphatic epoxides with LiX/HOAc, which proceed stereospecifically to yield only trans halohydrins.