Oxidative coupling of phenols. Part 6. A study of the role of spin density factors on the product composition in the oxidations of 3,5-dimethylphenol and phenol

Abstract

Oxidations of both 3,5-dimethylphenol and phenol with di-t-butyl peroxide at 140 °C gave as the major product the ortho-ortho-C–C coupled dimer, while oxidations with di-t-butyl peroxyoxalate at room temperature give much more of the ortho-para-C–C dimer. The results are not consistent either with the spin density distribution in the phenoxyl radical intermediates or with steric effects being the major factor which determines the product composition. It is proposed that the two phenoxyl radicals involved in coupling preferentially approach each other in a ‘sandwich-like’ manner with the oxygens in a 1,3-relationship.