E. Gibadullina, T. Shaekhov, A. K. Badrtdinov
Jun 1, 2014
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0
Influential Citations
7
Citations
Journal
Russian Chemical Bulletin
Abstract
Sterically hindered 2,6 dialkylphenols, being bio mimetics of natural antioxidant tocopherol (vitamin E), belong to a known class of widely used phenol antioxi dants.1 Development of polyfunctional antioxidants2,3 is one of the main trends in the last decades. Phosphorus containing ionol derivatives are efficient antioxidants, since the presence of several reaction centers in the molecule provides inhibition of oxidation processes following vari ous mechanisms: sterically hindered phenol fragment ef fects antiradical protection, whereas phosphoryl fragment is responsible for the inhibition in the reactions of other than radical decomposition of hydroperoxides.4,5 Reac tive and at the same time stable phosphorylated 2,6 di tert butyl 4 methylidene 2,5 cyclohexadienones are con venient reagents for the preparation of new functionally substituted organophosphorus derivatives.6,7 In the present work, we studied synthetic possibilities of phosphorylated 2,6 di tert butyl 4 methylidene 2,5 cyclohexadienones, viz., dimethyl [(3,5 di tert butyl 4 oxo 2,5 cyclohexadi enylidene)methyl]phosphonate (1a) and diphenyl [(3,5 di tert butyl 4 oxo 2,5 cyclohexadienylidene)methyl] phosphonate (1b) in the reactions with m phenylene diamine. The reaction of phosphorylated methylidenequinones with proton donating nucleophilic agents is known to fol low the scheme of nucleophilic 1,6 addition.8,9 We found that phosphorylated methylidenequinones 1a,b readily react with m phenylenediamine following earlier unknown pathway of electrophilic substitution in the aromatic ring with the formation of 1 : 1 products 2a,b in high yields (Scheme 1), rather than nucleophilic 1,6 addition at the free amino groups. The structure of compounds 2a,b was confirmed by 1H and 31P NMR and IR spectroscopy, their composition by mass spectrometry (MALDI TOF) and elemental analysis. To sum up, m phenylenediamine in the reactions with phosphorylated 2,6 di tert butyl 4 methylidene 2,5 cyclohexadienones acts as a C nucleophile with the for mation of the products of electrophilic substitution.