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首页> 外文期刊>Inorganic Chemistry: A Research Journal that Includes Bioinorganic, Catalytic, Organometallic, Solid-State, and Synthetic Chemistry and Reaction Dynamics >Nonheme manganese-catalyzed asymmetric oxidation. A lewis acid activation versus oxygen rebound mechanism: Evidence for the 'third oxidant'
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Nonheme manganese-catalyzed asymmetric oxidation. A lewis acid activation versus oxygen rebound mechanism: Evidence for the 'third oxidant'

机译：非血红素锰催化的不对称氧化。刘易斯酸活化与氧回弹机制：“第三种氧化剂”的证据

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摘要

The catalytic properties of a series of chiral nonheme aminopyridinylmanganese(II) complexes [LMn~(II)(OTf)_2] were investigated. The above complexes were found to efficiently catalyze enantioselective olefin oxidation to the corresponding epoxides with different oxidants (peroxycarboxylic acids, alkyl hydroperoxides, iodosylarenes, etc.) with high conversions and selectivities (up to 100%) and enantiomeric excesses (up to 79%). The effect of the ligand structure on the catalytic performance was probed. Epoxidation enantioselectivities were found to be strongly dependent on the structure of the oxidants (performic, peracetic, and m-chloroperbenzoic acids; tert-butyl and cumyl hydroperoxides; iodosylbenzene and iodosylmesitylene), thus bearing evidence that the terminal oxidant molecule is incorporated in the structure of the oxygen-transferring intermediates. High-valence electron-paramagnetic-resonance-active manganese complexes [LMn~(IV)=O]~(2+) and [LMn~(IV)(μ-O) _2Mn~(III)L]~(3+) were detected upon interaction of the starting catalyst with the oxidants. The high-valence complexes did not epoxidize styrene and could themselves only contribute to minor olefin oxidation sideways. However, the oxomanganese(IV) species were found to perform the Lewis acid activation of the acyl and alkyl hydroperoxides or iodosylarenes to form the new type of oxidant [oxomanganese(IV) complex with a terminal oxidant], with the latter accounting for the predominant enantioselective epoxidation pathway in the nonheme manganese-catalyzed olefin epoxidations.
机译：研究了一系列手性非血红素氨基吡啶基锰（II）配合物[LMn〜（II）（OTf）_2]的催化性能。发现上述络合物能以不同的氧化剂（过氧羧酸，氢过氧化氢烷基，碘基芳烃等）以高转化率和选择性（高达100％）和对映体过量（高达79％）有效地催化对映选择性烯烃氧化为相应的环氧化物。 。探讨了配体结构对催化性能的影响。发现环氧化对映选择性强烈依赖于氧化剂的结构（过甲酸，过氧乙酸和间氯过苯甲酸;叔丁基和枯基氢过氧化物;碘基苯和碘基甲基三甲苯），因此有证据表明末端氧化剂分子被并入结构中氧转移中间体。高价电子顺磁共振活性锰配合物[LMn〜（IV）= O]〜（2+）和[LMn〜（IV）（μ-O）_2Mn〜（III）L]〜（3+）在起始催化剂与氧化剂相互作用时检测到H 2O。高价络合物不会环氧化苯乙烯，它们本身只能对侧向的少量烯烃氧化做出贡献。然而，发现氧锰（IV）物种对酰基和烷基氢过氧化物或碘基芳烃进行路易斯酸活化，形成了新型氧化剂[具有末端氧化剂的氧锰（IV）络合物]，其中后者占主导地位非血红素锰催化的烯烃环氧化中的对映选择性环氧化途径。

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