The Oxidation of 3,6‐Di‐ tert ‐butyl‐2‐naphthol. – X‐Ray Analysis of 2,5,8,11‐Tetra‐ tert ‐butyl‐ peri ‐xanthenoxanthene

The oxidation of 3,6‐di‐ tert ‐butyl‐2‐naphthol ( 9 ) with 2,4,6‐tri‐ tert ‐butylphenoxyl in benzene leads to 3,3′,6,6′‐tetra‐ tert ‐butyl‐1,1′‐binaphthyl‐2,2′‐diol ( 5b ) or 2,5,8,11‐tetra‐ tert ‐butyl‐ peri ‐xanthenoxanthene ( 8b ). The structure of 8b has been determined by X‐ray analysis. In the presence of methanol/KOH 5b is oxidized by K 3 [Fe(CN) 6 ] to the ortho ‐quinol ether 17b , derived from 2,5,8,11‐tetra‐ tert ‐butyldibenzo[ a, kl ]xanthen‐1‐ol ( 12b ). The latter can be obtained from 17b by reduction via the corresponding aryloxenium cation 15b . The presence of the monovalent dehydrogenation product of 12b , the aryloxyl 14b , in the oxidation mixtures of 9 was demonstrated by ESR spectroscopy. The expected spirobenzoxete 7 could not be detected.