Es. Hand et al., MAGNESIUM METHYL CARBONATE-ACTIVATED ALKYLATION OF METHYL KETONES WITH AN OMEGA-HALO NITRILE, ESTERS, AND AMIDES, Journal of organic chemistry, 62(5), 1997, pp. 1348-1355
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.