Electrophilic Aromatic Substitution of Catechins: Bromination and Benzylation

Relative yields of C-6, C-8. and C-6 and C-8 substituted catechins obtained from the reaction of (+ )-catechin or 3' 4',57-tetra-O-methvl-( + )-catechin with pyridinium hydrobromide-perbromide, bromine. p-hydroxybenzyl al~oh~I, or o-hydroxybenZyI alcohol showed differing selectivities depending upon the electrophile used. Ratios of C-6 to C-8 substituted products were 1 : 1.2 for the reaction of p-hydroxybenzyl alcohol with (+) -catechin. 1 :2-3 for reaction of either bromine or o-hydroxybenzyl alcohol with (+)-catechin, and essentially exclusive substitution at the C-8 position in the reaction of tetra-O-methyt-(+)-catechin with bromine. Comparatively high proportions of 6-substituted and 6and 8-disubstituted producu were obtained in the reaction of (+ )-catechin with one equivalent of either por o-hydroxybenzyl alcohol.