New Opportunities for Duff Reaction

Abstract

Reaction of 2,4-di-tert-butylphenol with urotropin in conditions of Duff reaction takes an abnormal route and instead of the expected di-tert-butylsalicylaldehyde provides a mixture of N-substituted 3,5-di-tert-butyl-2-hydroxybenzylamines and redox conjugate benzoxazines containing mostly 6,8-di-tert-butyl-3-(3,5-di-tert-butyl-2-hydroxybenzyl)-2H-3,4-dihydrobenz[e][1,3]oxazine. A solvolysis of an individual benzoxazine in the system HO(CH2)2OH-H2O-HCl affords di(3,5-di-tert-butyl-2-hydroxybenzyl)amine, and in AcOH 3,5-di-tert-butylsalicilaldehyde. A mechanism of Duff reaction was suggested involving the formation of a benzoxazine intermediate.