Oxidation of organic sulfides by vanadium haloperoxidase model complexes.
Oxidation of organic sulfides by vanadium haloperoxidase model complexes.
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DOI：
10.1021/ic025650d
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发表时间：
2002-11
影响因子：
4.6
通讯作者：
Thomas S. Smith;V. Pecoraro
中科院分区：
文献类型：
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作者：
Thomas S. Smith;V. Pecoraro
除卤化物氧化外，钒的卤代过氧化物酶还能将硫化物氧化成亚硫化物。四个具有三脚醇胺配体的钒配合物，K[VO(O(2))(Heida)](1)，VO(2)(Bpg)(2)，K[VO(2)(Ada)](3)和K(2)[VO(2)(Nta)](4)，以前被证明执行溴氧化(Colpas，G.J.；Hamstra，B.J.；Kampf，J.W.；Pecoraro，V.L.J.am化学。SoC。1996、118、3469-3477)，现已证明可将芳烷基硫化物氧化成相应的亚硫醚。硫代苯甲醚在290 nm处的紫外光吸收消失，硫化物的(1)H-核磁共振谱芳香区发生变化，络合物的(51)V-核磁共振谱发生变化。在3h内，甲基苯硫醚的氧化量为1000当量(每个金属络合物)。氧化产物几乎完全是亚砜，生成的亚砜很少(在3小时内小于3%)。这与亲电氧化机理一致，如已提出的溴氧化1-4的机理。该速率在底物浓度下为一级反应，与溴化物氧化的速率规律相似。与溴氧化不同，激活过氧钒络合物所需的酸当量不会消耗。配合物1-4不与苯乙烯或环辛烯反应。我们将讨论这些反应与钒卤代过氧化物酶以及更一般的硫化物的过氧钒氧化反应的机理的相关性。
In addition to halide oxidation, the vanadium haloperoxidases are capable of oxidizing sulfides to sulfoxides. Four vanadium complexes with tripodal amine ligands, K[VO(O(2))(heida)] (1), VO(2)(bpg) (2), K[VO(2)(ada)] (3), and K(2)[VO(O(2))(nta)] (4), previously shown to perform bromide oxidation (Colpas, G. J.; Hamstra, B. J.; Kampf, J. W.; Pecoraro, V. L. J. Am. Chem. Soc. 1996, 118, 3469-3477), have now been shown to oxidize aryl alkyl sulfides to the corresponding sulfoxides. The oxidation was observed by the disappearance of thioanisole's ultraviolet absorption at 290 nm, by the change in the aromatic region of the (1)H NMR spectrum of the sulfides, and by changes in the complexes' (51)V NMR spectra. The amount of methyl phenyl sulfide oxidized in 3 h was 1000 equiv (per metal complex). The oxidation product is almost exclusively sulfoxide, with very little sulfone (less than 3% over a 3 h experiment) formed. This is consistent with an electrophilic oxidation mechanism, as had been proposed for oxidation of bromide by 1-4. The rate was found to be first order in substrate concentration, similar to the rate law observed for bromide oxidation. Unlike the bromide oxidation, the equivalent of acid required for peroxovanadium complex activation is not consumed. The complexes 1-4 are not reactive with styrene or cyclooctene. The relevance of these reactions to the mechanism of the vanadium haloperoxidases and, more generally, peroxovanadium oxygenation of sulfides will be discussed.