21449-69-4Relevant articles and documents
Electrochemical Dimerization of Phenylpropenoids and the Surprising Antioxidant Activity of the Resultant Quinone Methide Dimers
Romero, Kevin J.,Galliher, Matthew S.,Raycroft, Mark A. R.,Chauvin, Jean-Philippe R.,Bosque, Irene,Pratt, Derek A.,Stephenson, Corey R. J.
supporting information, p. 17125 - 17129 (2018/12/04)
A simple method for the dimerization of phenylpropenoid derivatives is reported. It leverages electrochemical oxidation of p-unsaturated phenols to access the dimeric materials in a biomimetic fashion. The mild nature of the transformation provides excellent functional group tolerance, resulting in a unified approach for the synthesis of a range of natural products and related analogues with excellent regiocontrol. The operational simplicity of the method allows for greater efficiency in the synthesis of complex natural products. Interestingly, the quinone methide dimer intermediates are potent radical-trapping antioxidants; more so than the phenols from which they are derived—or transformed to—despite the fact that they do not possess a labile H-atom for transfer to the peroxyl radicals that propagate autoxidation.
Oxygenation of tert-Butylphenols with an Unsaturated Side Chain
Nishinaga, Akira,Iwasaki, Hitoshi,Shimizu, Tadashi,Toyoda, Yasushi,Matsuura, Teru
, p. 2257 - 2266 (2007/10/02)
Base- and Co(Salpr)-promoted oxygenations of title compounds have been investigated with a view to obtaining further details concerning controlling factors in regioselective O2 incorporation into phenols.In the oxygenation of 4-alkenyl-2,6-di-tert-butyl- and 2-alkenyl-4,6-di-tert-butylphenols (1 and 12), the reactivity of the substrates and regioselectivity in the O2 incorporation may be interpreted in terms of electronic and steric effects of the alkenyl group as well as association effect of the countercation K+ on the transition-state 26 involving a charge transfer from the substrate anion to O2.With 4-alkynyl-2,6-di-tert-butylphenols (21), dioxygen was incorporated exclusively into the ortho position only when the phenolate anion was associated with K+.On the contrary, in the oxygenation of 1 and 12 with Co(Salpr), O2 was incorporated exclusively into the alkynyl side chain, regardless of the nature of the substituent, whereas with 21, O2 incorporation was distributed to both the ortho and the alkenyl side chain.The substituent-dependent regioselectivity in the oxygenation of phenols with Co(Salpr) is because the reactive phenolate-COIII species undergo homolysis to form phenoxy radical-CoII species reversibly, whose oxygenations compete with each other.When the oxygenation of the anionic species predominates, O2 is incorporated into the ortho position, whereas with the radical species the para and side chain oxydations predominate.
