Oxidation of alkoxyphenols. Part 23. A re-examination of the reaction of 5,5′-dimethoxy-3,3′-di-t-butylbiphenyl-2,2′-diol with lead tetra-acetate : crystal structure of the product

Abstract

The major product of the reaction, previously described as an acetoxybenzoxet, is now shown to be 4,10a-dihydro-7-methoxy-4-oxo-2,9-di-t-butyloxepino[2,3-b]benzofuran-10a-yl acetate (4). This assignment is based on X-ray crystallographic analysis of the corresponding benzoate. The biphenyl system is re-formed on reduction of the acetate, and reaction with acid converts the acetate into benzofuran-3(2H)-one derivatives.