Methoxylated arylpyruvic acids

In connection with our studies on the dimerisation of aylethanals and arylacetones with boron tribromide, we first turn to the reaction of methoxylated arylpyruvic acids [38], Arylpyruvic acids that were obtained mainly in their Z-enol form, did not dimerise. When the ortho aromatic position is unsubstituted, only an isomerisation occurs that allowed us to isolate some 2-hydroxyarylpropenoic acids in their E-form. In the cases of (2-methoxyphenyl)arylpropenoic acids, cyclisations were also observed leading of mixtures of benzofuran-2-carboxylic acids and 3-hydroxycoumarins that are easily separated, Fig. (12). We observed a competition between cyclisation and isomerisation that have apparently similar kinetic parameters. 

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