The courses of alkylation have been studied of phenol, 4-methylphenol, 2, 6-di-tert. butylphenol and pyrocatechol and its homo] ogues by the trimers of isobutylene in the presence of boron trifluoride etherate. It has been proved that the synthesis of the tert. dodecyl derivatives requires the use of the so-called" higher-boiling" triisobutylene, ie mixture of 2, 4, 4, 6, 6 pentamethyll-and-2-heptene.