MAGNESIUM METHYL CARBONATE-ACTIVATED ALKYLATION OF METHYL KETONES WITH AN OMEGA-HALO NITRILE, ESTERS, AND AMIDES

Terminally substituted, extended-chain derivatives of the 2-dibenzofur anyl methyl ketone 6 and its phenylethyl analogue 12 were readily obta ined by converting the ketones to magnesium chelates of their beta-car boxylated enolates with magnesium methyl carbonate (MMC, methyl methox ymagnesium carbonate, Stiles's reagent), followed by alkylation in sit u with omega-halo compounds, X(CH2)(n)Y where X = Br and Y = CO(2)Me, CN, CONMe(2), CON(i-Pr)(2), CON(CH2)(4), or CON(CH2)(5) for n = 1; X = Br or I, and Y = CO(2)Me for n = 2; and X = Br and Y = CO(2)Me for n = 3. Dimethylcarbamoyl chloride (n = 0) gave products derived from MMC and the solvent, N,N-dimethylformamide. The order of reactivity of th e halides was alpha > beta > gamma and beta-I > beta-Br. beta-Bromo am ides were found to be unsuitable reactants. Lower reaction temperature s favored alkylation over competing elimination of HX from methyl beta -halopropionate. No self-condensation products of the ketones were obs erved; however, bis-alkylation and monomethylation products were forme d when reaction times were prolonged. In contrast to the unsubstituted beta-keto acid 13, all intermediate alpha-alkyl beta-keto acids decar boxylated during the reaction or the workup.