Uppsala University, Department of Chemistry, BMC, Box 576, SE-751 23 Uppsala, Sweden.
J Org Chem. 2013 Jun 21;78(12):6008-15. doi: 10.1021/jo400703w. Epub 2013 Jun 11.
The quenching of peroxyl radicals by ortho-(alkyltelluro)phenols occurs by a more complex mechanism than formal H-atom transfer. In an effort to improve on this concept, we have prepared (alkyltelluro)resorcinols and bis(alkyltelluro)phenols and evaluated their catalytic chain-breaking and preventive antioxidative properties. The in situ formed trianion produced from 2-bromophenol and 3 equiv of tert-butyllithium was allowed to react with dialkyl ditellurides to provide ortho-(alkyltelluro)phenols in low yields. 2-Bromoresorcinols after treatment with 4 equiv of tert-butyllithium similarly afforded 2-(alkyltelluro)resorcinols. Bis(alkyltelluro)phenols were accessed by allowing the trianion produced from the reaction of 2,6-dibromophenol with 5 equiv of tert-butyllithium to react with dialkyl ditellurides. The novel phenolic compounds were found to inhibit azo-initiated peroxidation of linoleic acid much more efficiently than α-tocopherol in a two-phase peroxidation system containing excess N-acetylcysteine as a stoichiometric thiol reducing agent in the aqueous phase. Whereas most of the (alkyltelluro)phenols and resorcinols could inhibit peroxidation for only 89-228 min, some of the bis(alkyltelluro)phenols were more regenerable and offered protection for >410 min. The novel (alkyltelluro)phenols were also evaluated for their capacity to catalyze reduction of hydrogen peroxide in the presence of thiophenol (glutathione peroxidase-like activity). (Alkyltelluro)resorcinols 7a-c were the most efficient catalysts with activities circa 65 times higher than those recorded for diphenyl diselenide.
邻（烷基亚碲基）苯酚通过比形式上的 H 原子转移更复杂的机制淬灭过氧自由基。为了改进这一概念，我们制备了（烷基亚碲基）间苯二酚和双（烷基亚碲基）苯酚，并评估了它们的催化链断裂和预防性抗氧化性能。由 2-溴苯酚和 3 当量的叔丁基锂原位形成的三阴离子与二烷基二碲化物反应以低产率提供邻（烷基亚碲基）苯酚。用 4 当量的叔丁基锂处理 2-溴间苯二酚同样得到 2-（烷基亚碲基）间苯二酚。通过允许由 2,6-二溴苯酚与 5 当量的叔丁基锂反应生成的三阴离子与二烷基二碲化物反应，得到双（烷基亚碲基）苯酚。在包含过量 N-乙酰半胱氨酸作为水相中的化学计量硫醇还原剂的两相过氧化体系中，新型酚类化合物被发现比α-生育酚更有效地抑制偶氮引发的亚油酸过氧化。虽然大多数（烷基亚碲基）苯酚和间苯二酚只能抑制过氧化 89-228 分钟，但一些双（烷基亚碲基）苯酚更可再生，并提供>410 分钟的保护。新型（烷基亚碲基）苯酚也被评估了其在存在巯基酚（谷胱甘肽过氧化物酶样活性）时催化过氧化氢还原的能力。（烷基亚碲基）间苯二酚 7a-c 是最有效的催化剂，其活性比二苯基二硒化物高约 65 倍。
