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Cyclization by C(sp3)–H Arylation with a Transient Directing Group for the Diastereoselective Preparation of Indanes
ACS Catalysis ( IF 11.3 ) Pub Date : 2021-02-24 , DOI: 10.1021/acscatal.0c05081 Philip A. Provencher 1 , Katherine L. Bay 2 , John F. Hoskin 1 , K. N. Houk 2 , Jin-Quan Yu 3 , Erik J. Sorensen 1
ACS Catalysis ( IF 11.3 ) Pub Date : 2021-02-24 , DOI: 10.1021/acscatal.0c05081 Philip A. Provencher 1 , Katherine L. Bay 2 , John F. Hoskin 1 , K. N. Houk 2 , Jin-Quan Yu 3 , Erik J. Sorensen 1
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We report Pd(II)-catalyzed cyclative C(sp3)–H arylation of ketones with a transient directing group (TDG). Based on calculations, the oxidative addition step implicates a highly strained trigonal bipyramidal geometry around a Pd(IV) intermediate afforded by the bidentate TDG and the intramolecular arylation process. As a consequence, unproductive protodeiodination outcompetes the cyclative arylation Pd(II/IV) pathway under standard conditions. The desired selectivity was achieved by prudent selection of the TDG and the Ag(I) source. The reaction is accelerated by the inclusion of stoichiometric quantities of trifluoroacetic acid, which benefits both the palladium catalysis and the attachment of the TDG for the pivotal C(sp3)–H palladation. Critically, the use of the 2-pyridone ligand improves yields significantly and enables the cyclative arylation of both methyl and linear methylene C–H bonds. Mechanistically, the high energy barrier associated with the transition state of this cyclization type is sufficient to drive selective linear methylene C–H activation in the presence of a more reactive methyl C–H bond. The reaction is showcased in a two-step synthesis of a substituted indane using 3-iodoanisole as the linchpin in a formal [3 + 2] annulation concept featuring two C(sp3)–H arylations.
中文翻译：
C（sp 3）–H芳基化与瞬态指导基团的非对映选择性制备茚满环的环化反应
我们报告了酮与瞬态导向基团（TDG）的Pd（II）催化的环化C（sp 3）-H芳基化反应。基于计算，氧化加成步骤牵涉到由双齿TDG和分子内芳基化过程提供的Pd（IV）中间体周围的高应变三角形双锥体几何结构。结果，在标准条件下，非生产性原碘化作用胜过环化芳基化Pd（II / IV）途径。通过谨慎选择TDG和Ag（I）离子源可以达到所需的选择性。通过加入化学计量的三氟乙酸可加快反应速度，这对钯催化和TDG对关键C（sp 3的连接）都有利。）–H palpalation。至关重要的是，使用2-吡啶酮配体可显着提高产率，并使甲基和线性亚甲基C–H键的环芳基化反应成为可能。从机理上讲，与这种环化类型的过渡态相关的高能垒足以在存在更活泼的甲基CH键的情况下驱动选择性的线性亚甲基CH键活化。该反应在3- [十二烷基]正构环构概念中，以3-碘苯甲醚为关键，通过两步合成取代的茚满，展示了两个C（sp 3）-H芳基化作用。
更新日期：2021-03-05
中文翻译：
C（sp 3）–H芳基化与瞬态指导基团的非对映选择性制备茚满环的环化反应
我们报告了酮与瞬态导向基团（TDG）的Pd（II）催化的环化C（sp 3）-H芳基化反应。基于计算，氧化加成步骤牵涉到由双齿TDG和分子内芳基化过程提供的Pd（IV）中间体周围的高应变三角形双锥体几何结构。结果，在标准条件下，非生产性原碘化作用胜过环化芳基化Pd（II / IV）途径。通过谨慎选择TDG和Ag（I）离子源可以达到所需的选择性。通过加入化学计量的三氟乙酸可加快反应速度，这对钯催化和TDG对关键C（sp 3的连接）都有利。）–H palpalation。至关重要的是，使用2-吡啶酮配体可显着提高产率，并使甲基和线性亚甲基C–H键的环芳基化反应成为可能。从机理上讲，与这种环化类型的过渡态相关的高能垒足以在存在更活泼的甲基CH键的情况下驱动选择性的线性亚甲基CH键活化。该反应在3- [十二烷基]正构环构概念中，以3-碘苯甲醚为关键，通过两步合成取代的茚满，展示了两个C（sp 3）-H芳基化作用。
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