Electrochemically-induced spirolactonization of alpha-(methoxyphenoxy)alkanoic acids into quinone ketals.

Anodic oxidation of two series of alpha-(2)- and alpha-(4-methoxyphenoxy)alkanoic acids were studied both at the analytical and preparative scales in order to delineate mechanistic aspects of electrochemically induced spirolactonization and to develop synthetically useful orthoquinone bis- and monoketals. Although alpha-monomethylated carboxylic acids and acetic acid derivatives do not undergo any spiroannulation, alpha-dimethylated carboxylic acids furnished spirolactones in high yields. A gem-dimethyl effect is invoked to explain these differences in cyclization capacity.