Alkoxycarbonyl- and Carboxylate-Group Migrations in the Benzilic Acid Rearrangement of Ethyl Cyclopropane-2, 3-dioxopropionate

In alkaline medium C₃H₅? CO? C (OH)₂? COOEt ( 1b ) is transformed into C₃H₅? C (OH)(COOH)₂ ( 2a ). Labelling experiments show that the cyclopropyl group is not shifted, but only ROOC and/or ^?O₂C groups. GC./MS. and NMR. analysis after incomplete reaction show that both ROOC- and ^?O₂C-groups Migrate; at higher pH (ca. 14) the ester group rearrangement seems to be more important than at pH ca.9-10.