Unstable 1,1,2-Enetriols as (Probable) Intermediates in the Decarboxylation of α,β-Diketo Acids

Article abstract of DOI:10.1021/jo00009a029

During the acid hydrolysis of (hydrated) 4-aryl-2,3-diketobutyramide 2 (aryl = phenyl, o-chlorophenyl, p-methoxyphenyl), 3-aryllactic acid (5) is formed by rapid decarboxylation of the intermediate diketo acid (3).In the decarboxylation step, a further unstable intermediate is formed.The latter manifests itself by reducing 1 mol of added iodine during the hydrolysis-decarboxylation reaction, thereby forming 3-arylpyruvic acid (6), isolated instead of 5.Thus, the oxidation of the unstable intermediate by iodine is more rapid than its ketonization.It is formulated as an 1,1,2-enetriol (4), more probably than an α-hydroxyketone.