Improved Preparation of Methyl 3-Oxo-1-cyclohexene-1-carboxylate and Its Use in the Synthesis of Substituted 1,5-Cyclodecadienes

Article abstract of DOI:10.1021/jo00147a009

An improved preparation of methyl 3-oxo-1-cyclohexene-1-carboxylate (6) is reported in which cyclohexanecarboxylic acid is converted to methyl 1-bromocyclohexanecarboxylate by a variation of the Hell-Volhard-Zelinsky reaction and then the bromo ester is dehydrohalogenated with quinoline and the resultant unsaturated ester is oxidized at an allylic position with chromium trioxide in acetic acid and acetic anhydride to give 6.The overall conversion proceeds in 49percent yield, which is a substantial improvement over previous attempts reported for this sequence.Photoadditionof 6 and cyclobutene-1-carboxylic acid yields adduct 8, which after esterification and thermolysis gives the 1,5-cyclodecadiene 12.In addition, reduction of adduct 8 with NaCNBH3 followed by spontaneous lactoniaztion yields 10, which upon thermolysis gives the lactone diene 11.This approach should have applications in the synthesis of germacranolides that have an ester or related carbonyl function on C(14).