Specific Features of Reactions of Halomethyl Derivatives of Alkyl 5-Isobutylfuran-3-carboxylates with Trimethyl Phosphite and Sodium Diethyl Phosphite

Ethyl 5-isobutyl-2-methylfuran-3-carboxylate is selectively brominated with N-bromosuccin-imide by the methyl group to give an unstable bromide. The latter on heating or in the presence of bases un-dergoes dehydrobromination accompanied by rearrangement, leading to a (2'2-dimethylvinyl)furan derivative.Phosphorylation of this bromide with trimethyl phosphite gives a 2-dimethoxyphosphorylmethyl derivativeand a product containing the phosphonate group to the isobutyl radical. Chloromethylation of the startingester proceeds in the 4 position of the furan ring. The resulting chloride undergoes phosphorylation underconditions of the Michaelis-Becker reaction to give the corresponding 4-(dialkoxyphosphorylmethyl)furan'and under the action of trimethyl phosphite a mixture of the same phosphonate, a dehalogenation producthaving a dimethylvinyl fragment. Bromination of the 4-chloromethyl derivative with N-bromosuccinimideinvolves the 2-methyl group. The dihalide reacts with trimethyl phosphite by way of reduction of the bromomethyl group to give 4-chloromethyl- or 4-dimethoxyphosphorylmethyl derivatives, as well as analogous dehydrohalogenation products containing a 5-dimethylvinyl fragment. A scheme describing the sequence of formation of these products in the course of the reaction is offered.