Alkyltelluro Substitution Improves the Radical‐Trapping Capacity of Aromatic Amines

Abstract

The synthesis of a variety of aromatic amines carrying an ortho-alkyltelluro group is described. The new antioxidants quenched lipidperoxyl radicals much more efficiently than α-tocopherol and were regenerable by aqueous-phase N-acetylcysteine in a two-phase peroxidation system. The inhibition time for diaryl amine 9 b was four-fold longer than recorded with α-tocopherol. Thiol consumption in the aqueous phase was found to correlate inversely to the inhibition time and the availability of thiol is the limiting factor for the duration of antioxidant protection. The proposed mechanism for quenching of peroxyl radicals involves O-atom transfer from peroxyl to Te followed by H-atom transfer from amine to alkoxyl radical in a solvent cage.

Double CH Activation of a Masked Cationic Bismuth Amide

“…90 %d euteration grade) or an iodine substituent were introduced at the ortho-phenyl position (Scheme 5, left). [25][26][27][28] In summary,w eh ave shown that highly selective single and double ortho-CH activation reactions of diphenylamide, (NPh 2 ) À ,a re feasible upon incorporation of this ligand into ac ationic bismuth complex. [23] Current routes to orthoiododiphenylamines (related to 4b)r ely on palladium catalysis and comparatively forcing conditions (100 8 8C, 24 h) or the use of benzyne precursors.…”

“…[11] In main-group chemistry,t he reaction of HNPh 2 with nBuLi in a3 :7 stoichiometry afforded the more complicated cluster [(Ph 2 NLi)[Ph(C 6 H 4 Li)NLi] 2 (nBuLi) 2 (Et 2 O) 4 ], containing two ortho-metalated diphenylamide groups,a fter af ew days. 28(2) ). [13,14] Under optimized reaction conditions, 2 crystallized directly from the reaction mixture at 23 8 8Ca fter about 16 h, and was isolated in 91 %overall yield as ayellow solid.…”

Regenerable Radical-Trapping Tellurobistocopherol Antioxidants

“…The experimental setup for determination of the rate of NAC-consumption in the two-phase lipid peroxidation model was recently described. 13 The values reported are means ± SD based on triplicates.…”

“…1 H, 13 C and 125 Te NMR data for all new compounds prepared. This material is available free of charge via the Internet at http://pubs.acs.org.…”

“…Following a recently described procedure, 13 the aqueous phase was sampled every 30 minutes and the thiol was allowed to react with bis-4-pyridyl disulfide. The concentration of pyridine-4-thiol formed (eq 4), as determined by UV-spectroscopy at 324 nm, was used for monitoring the disappearance of NAC with time.…”