Rearrangement to catechinic acid

In addition to the effect pH has on the overall reaction rate, it is also important to note the effect of pH on rearrangement reactions of (+)-catechin. At alkaline pH, these secondary rearrangement reactions dominate. Epimerization of (+)-catechin to (-b)-epicatechin is a prominent reaction at pH 9.0. This is not serious in terms of adhesive formulation because it does not alter the reactivity of the aromatic nucleus toward condensation with benzyl alcohols. However, in reactions at pH 10.0 or 11.0, the intramolecular rearrangement to catechinic acid dominates and results in loss of the phloroglucinol functionality. 

Kiatagrajai P, WeUons JD, Golob L, White JD J. Kinetics of epimerization of (+) catechin and its rearrangement to catechinic acid. Org Chem 1982 47 2910-2912. Kennedy JA, Munro MHG, Powell HKJ, Porter LJ, Foo Y. The protonation reactions of catechin, epicatechin and related compounds. Aust J Chem 1984 38 885-892. 

Until recently, little attention has been given to the reactions of polymeric proanthocyanidins under alkaline conditions. It was known that solution of polymeric procyanidins in base caused a marked decrease in the reactivity of these polymers with aldehyde and that both carbonyl and relatively acidic functions were generated analogous to the rearrangement of catechin to catechinic acid (152, 335). 

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