Regioselective Ring Cleavage of Phenyl- or/and Alkyl- Substituted Epoxides with Al-Methanesulfonyldiisobutylalane

Abstract

C. The regioselectivities shown in these reactions of one alkyl- or phenyl- substituted epoxides such as 1,2-epoxybutane and styrene oxide are extraordinary. The reagent attacked only the more hindered site of epoxy ring to produce the corresponding primary alcohol as a sole product. These results clearly indicate that the reaction proceed s through trapping of β-hydrogen from isobutyl group of the reagent at the site best able to accommodate a carbocation. Such interpretation was further confirmed by the results obtained from the reaction of more substituted epoxides such as 2,3-epoxy-2-methylbutane and α-methylstyrene oxide: the products are 3-methyl-2-butanol and 2-phenyl-1-propanol, respectively. Again, the selectivities are perfects.Particularly interesting example is the reaction of