Oxidative dimerization of methyl (E)-4-hydroxy-3,5-di-t-butylcinnamate with potassium ferricyanide

Abstract

The title compound on oxidation with alkaline potassium ferricyanide or 2,4.6-tri-t-butylphenoxyl gives a mixture of threo- and erytho-bisquinone methides (3) and (4) in the ratio 65 :35 by coupling of C(β)-radical intermediates (2). The configuration of isomer (3) follows from its conversion into trans-3,4-bis-(4-hydroxy-3,5-di-t-butyl-benzyl)tetrahydrofuran (10), which is also obtained from the diarylperhydrofurofuran (6). It is suggested that the non-stereospecific oxidative coupling of the phenol (1) is due to the bulky t-butyl groups impeding the formation of a dimeric reaction intermediate which would lead to exclusive threo-coupling as in other (E)-propenylphenol derivatives.