Alkylation of CH acids in the presence of potassium carbonate. III. Alkylation of CH acids by 2,3-substituted 1,4-dibromo-2-butenes

During the cycloalkylation of CH acids by 2,3-substituted (methyl-chlorine) 1,4-dibromo-2-butenes the direction of intramolecular C- and O-alkylation depends both on steric and on electronic factors. The introduction of substituents into the alkylating agent and the presence of acetyl groups in the initial CH acids promote regiospecific intramolecular O-alkylation. It was found that the initial alkylation of the enolizing CH acids with 1,4-dibromo-2-methyl-2-butene in the presence of potassium carbonate takes place with high regioselectivity at the unsubstituted end of the butene chain.