Selective Preparation. 31. Oxidative Coupling of 2-Halo-4,6-di-tert-butylphenols with Potassium Hexacyanoferrate (III) in Benzene

Article abstract of DOI:10.1021/jo00332a004

When 2-bromo-4,6-di-tert-butylphenol (1b) was treated with K3Fe(CN)6 in benzene, 1,4-dihydro-4-bromo-2,4,6,8-tetra-tert-butyl-1-oxodibenzofuran (3) was obtained in 81percent yield together with a small amount of 2,4,6,8-tetra-tert-butyldibenzofuran (4).Heating of 3 in primary alcohols such as methanol and ethanol afforded the corresponding 1,4-dihydro-4-alkoxy-2,4,6,8-tetra-tert-butyl-1-oxodibenzofuran (9) in good yields.However, treatment of 3 with boiling isopropyl alcohol gave in 85percent yield 1-hydroxy-2,4,6,8-tetra-tert-butyldibenzofuran (5), which afforded 1-hydroxydibenzofuran (6) by its AlCl3-catalyzed trans tert-butylation in toluene.Compound 6 was obtained also by the AlCl3-catalyzed trans alkylation of 3.Similar trans alkylation of 4 afforded dibenzofuran (19). 1-Hydroxy-4-methoxy- (11) and 1,4-dihydro-1,4-dioxo-2,6,8-tri-tert-butyldibenzofuran (12) were also prepared from compound 3.Similar oxidation of 2-chloro-4,6-di-tert-butylphenol (1c) afforded 6,6'-bis<2,4-di-tert-butyl-6-chlorocyclohexa-2,4-dien-1-one> (22) and 2,4-di-tert-butyl-4-chloro-6-(2,4-di-tert-butyl-6-chlorophenoxy)-cyclohexa-2,5-dien-1-one (23) in 23percent and 53percent yields, respectively.However, oxidation of 2-fluoro-4,6-di-tert-butylphenol (1d) gave only one product, 2,4-di-tert-butyl-4-fluoro-6-(2,4-di-tert-butyl-6-fluorophenoxy)-cyclohexa-2,5-dien-1-one (36), in 63percent yield.The mechanisms of oxidation of 2-halo-4,6-di-tert-butylphenols with K3Fe(CN)6 in benzene were also discussed in this paper.