Alkylpyrocatechols are dealkylated by AIBr 3 in CH2Br2. The formation of stable carbenium ions (!eft-butyl, methylcyclopentyl, and l-adamantyl) was detected by tH NMR spectroscopy. PyrogaUol and 2,3-dihydroxynaphthalene are coordinated with AIBr 3 in the tautomeric keto form, and 2-raercapto-4-methylphenol forms a complex in the hydroxy form.Key words: pyrocatechol derivatives, multiatomic phenols, complexes, A1Br3, dealky[ation.It has been previously shown that in the presence of aluminum halides, naphthols and methylated phenols undergo tautomeric transformations with the migration of a proton of the hydroxy group to the ring. t-4 The reactions of multiatomic phenols with Lewis acids in nonaqueous solutions are poorly studied. However, it is known that under the action of BF3, resorcinol, 5-methylresorcinol, and phloroglucinol are transformed into complexes of the tautomeric keto form. sIn the present work, the reactions of A1Br 3 with pyrocatechol, 4-tert-butyl-, 4-cyclohexyl-, 4-(1-adamantyl)-, 3,5-di-tert-butyl-, 3,5-di-tert-butyl-6-(piperidyl-l-methyl)-, and 3,5-di(1-adamantyl)pyrocatechols, as well as with pyrogallol, 2,3-dihydroxynaphthalene, and 2-mercapto-4-methylphenol, in CH2Br 2 were studied. Taking into account the rather high stability of tautomeric keto forms of hindered phenols, s we proposed that pyrocatechols with bulky substituents in the ring can give complexes in the tautomeric keto form.Alkylpyrocatechols were added to a suspension of A1Br 3 in CH2Br ~ (1 " 3) that was cooled to -30 ~ Solid complexes, which can be dissolved at 20 ~ were L precipitated from the mixture. Deeply colored solutions of complexes were immediately formed from 2,3-dihydroxynaphthalene, pyrogallol, and 2-mercapto-_. _ 4-methylphenol.The lH NMR spectrum of the mixture of 4-terrbutylpyrocatechol with A1Br3 at 20 ~ (Fig. I, spec-