REACTIONS OF PHENOLS WITH THIANTHRENE CATION RADICAL

The phenols 2-R1-6-R2-phenol 1a-g in which R1 = R2 = tert-butyl, methyl, isopropyl, Cl, Br, F, and H reacted with thianthrene cation radical perchlorate (Th.+ClO4-) to give 5-(4-hydroxyaryl)thianthreniumyl perchlorates 2a-g in good yield. o-Allylphenol (1i) behaved similarly. o-tert-Butylphenol (1h) gave both 5-(3-tert-butyl-4-hydroxyphenyl)thianthreniumyl perchlorate (2h) and a quinonoidal perchlorate (3), namely, 5-(3-thianthreniumyl-5-tert-butyl-6-oxo-2,4-cyclohexadien-1-ylidene)-5,5-dihydrothianthrene perchlorate. The 2,6-di-tert-butyl-4-R3-phenols 4a-c, R3 = tert-butyl, methoxy, and methyl, reacted with Th.+ClO4- in nitrile solvents (RCN) to give 2-R-5-R3-7-tert-butylbenzoxazoles 5a-e. The tert-butyl group that was displaced by RCN in forming 5 was converted into t-BuNHCOR (8), tert-butyl alcohol, and isobutene. In contrast, 2-tert-butyl-4,6-dimethylphenol (9) gave, in CH3CN, 4-tert-butyl-2,5,7-trimethylbenzoxazole (11), that is, with migration of the displaced tert-butyl group. The reactions of 4-tert-butylphenol (14) and 2,4-di-tert-butylphenol (17) are also described.