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首页> 美国卫生研究院文献>other >Enantioselective Iridium Catalyzed Carbonyl Allylation from the Alcohol or Aldehyde Oxidation Level via Transfer Hydrogenative Coupling of Allyl Acetate: Departure from Chirally Modified Allyl Metal Reagents in Carbonyl Addition
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Enantioselective Iridium Catalyzed Carbonyl Allylation from the Alcohol or Aldehyde Oxidation Level via Transfer Hydrogenative Coupling of Allyl Acetate: Departure from Chirally Modified Allyl Metal Reagents in Carbonyl Addition

机译：对映选择性铱通过乙酸烯丙酯的转移加氢偶联从醇或醛的氧化级催化羰基烯丙基化：脱除羰基加成中的手性改性烯丙基金属试剂

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摘要

Under the conditions of transfer hydrogenation employing an iridium catalyst generated in situ from [Ir(cod)Cl]2, the chiral phosphine ligands (R)-BINAP or (R)-Cl,MeO-BIPHEP and m-nitrobenzoic acid, allyl acetate couples to allylic alcohols >1a->1c, aliphatic alcohols >1d->1l and benzylic alcohols >1m->1u to furnish products of carbonyl allylation >3a->3u with exceptional levels of asymmetric induction. The very same set of optically enriched carbonyl allylation products >3a->3u are accessible from enals >2a->2c, aliphatic aldehydes >2d->2l and aryl aldehydes >2m->2u, using iridium catalysts ligated by (-)-TMBTP or (R)-Cl,MeO-BIPHEP under identical conditions, but employing isopropanol as a hydrogen donor. As corroborated by single crystal X-ray diffraction, the active catalyst is the cyclometallated complex >V, which arises upon ortho-C-H insertion of iridium onto m-nitrobenzoic acid. The results of isotopic labeling are consistent with intervention of symmetric iridium π-allylationl intermediates or rapid interconversion of σ-allyl haptomers through the agency of a symmetric π-allyl. Competition experiments demonstrate rapid and reversible hydrogenation-dehydrogenation of the carbonyl partner in advance of C-C coupling. The coupling products, which are homoallylic alcohols, experience very little erosion of optical purity by way of redox equilibration under the coupling conditions, although isopropanol, a secondary alcohol, may serve as terminal reductant. A plausible catalytic mechanism accounting for these observations is proposed, along with a stereochemical model that accounts for the observed sense of absolute stereoinduction. This protocol for asymmetric carbonyl allylation transcends the barriers imposed by oxidation level and the use of preformed allyl-metal reagents.
机译：在使用由[Ir（cod）Cl] 2原位生成的铱催化剂进行转移氢化的条件下，手性膦配体（R）-BINAP或（R）-Cl，MeO-BIPHEP和间硝基苯甲酸乙酸烯丙酯配对到烯丙醇> 1a -> 1c ，脂族醇> 1d -> 1l 和苯甲醇> 1m -> 1u ，可提供羰基烯丙基化> 3a -> 3u 的产品，并具有非对称诱导水平。可以从脂族的> 2a -> 2c 烯醇中获得完全相同的一组光学富集的羰基烯丙基化产物> 3a -> 3u 醛（strong）2d -> 2l 和芳基醛> 2m -> 2u ，使用通过（-）-TMBTP或（R）-Cl，MeO-BIPHEP在相同条件下，但采用异丙醇作为氢供体。正如单晶X射线衍射所证实的那样，活性催化剂是环金属化的配合物> V ，它是将铱邻-C-H插入间硝基苯甲酸而生成的。同位素标记的结果与对称铱π-烯丙基化中间体的干预或通过对称π-烯丙基的作用使σ-烯丙基触角的快速相互转化相一致。竞争实验表明，在进行C-C偶联之前，羰基伙伴快速且可逆地进行加氢-脱氢。尽管异丙醇（一种仲醇）可以用作末端还原剂，但偶合产物（均丙醇）在偶联条件下通过氧化还原平衡几乎不会破坏光学纯度。提出了一种合理的催化机制，解释了这些观察结果，以及提出了一种立体化学模型，该模型解释了所观察到的绝对立体诱导感。这种不对称羰基烯丙基化的方案超越了由氧化水平和使用预先形成的烯丙基金属试剂所施加的障碍。

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