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Unveiling the Takai Olefination Reagent via Tris(tert-butoxy)siloxy Variants
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2018-09-14 , DOI: 10.1021/jacs.8b08739
Daniel Werner 1 , Reiner Anwander 1
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2018-09-14 , DOI: 10.1021/jacs.8b08739
Daniel Werner 1 , Reiner Anwander 1
Affiliation
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The elusive Takai olefination reagent, namely, the iodo-methylidene Cr(III) complex [Cr2Cl4(CHI)(thf)4], has been isolated by careful handling of the reaction between CrCl2 and CHI3 in THF at -35 °C. Alternatively, treatment of [Cr(OSi(O tBu)3)2] with CHI3 gave the mixed-valent dihalido-methanide complex [CrII/III2I2(OSi(O tBu)3)2(CHI2)], featuring a Cr(III)-CHI2 moiety. In the presence of TMEDA nucleophilic attack at CHI2 occurred generating the zwitterionic species [CrIII(OSi(O tBu)3)2(tmeda-CHI)][I]. Complexes [Cr2Cl4(CHI)(thf)4] and [CrII/III2I2(OSi(O tBu)3)2(CHI2)] were screened for their ability to induce monohalido olefination of benzaldehyde. Remarkably, both complexes promote olefination, with [Cr2Cl4(CHI)(thf)4] accomplishing the same E selectivity as Takai 's original mixture. Complex [CrII/III2I2(OSi(O tBu)3)2(CHI2)], however, appeared to give preferentially Z isomer, corroborating the monoiodo-methylidene species Cr(III)-CHI-Cr(III) as the active olefination component of the original in situ generated Takai reagent mixture.
中文翻译：
通过三（叔丁氧基）甲硅烷氧基变体揭开 Takai 烯烃化试剂的面纱
难以捉摸的 Takai 烯化试剂，即碘-亚甲基 Cr(III) 配合物 [Cr2Cl4(CHI)(thf)4]，已通过小心处理 CrCl2 和 CHI3 在 THF 中的反应在 -35 °C 下分离出来。或者，用 CHI3 处理 [Cr(OSi(O tBu)3)2] 得到混合价二卤代甲烷复合物 [CrII/III2I2(OSi(O tBu)3)2(CHI2)]，具有 Cr(III) )-CHI2 部分。在 TMEDA 存在下，CHI2 发生亲核攻击，生成两性离子物质 [CrIII(OSi(O tBu)3)2(tmeda-CHI)][I]。筛选了配合物 [Cr2Cl4(CHI)(thf)4] 和 [CrII/III2I2(OSi(O tBu)3)2(CHI2)] 诱导苯甲醛单卤代烯烃化的能力。值得注意的是，这两种配合物都促进了烯化，[Cr2Cl4(CHI)(thf)4] 实现了与 Takai 原始混合物相同的 E 选择性。然而，复合物 [CrII/III2I2(OSi(O tBu)3)2(CHI2)]，
更新日期：2018-09-14
中文翻译：
通过三（叔丁氧基）甲硅烷氧基变体揭开 Takai 烯烃化试剂的面纱
难以捉摸的 Takai 烯化试剂，即碘-亚甲基 Cr(III) 配合物 [Cr2Cl4(CHI)(thf)4]，已通过小心处理 CrCl2 和 CHI3 在 THF 中的反应在 -35 °C 下分离出来。或者，用 CHI3 处理 [Cr(OSi(O tBu)3)2] 得到混合价二卤代甲烷复合物 [CrII/III2I2(OSi(O tBu)3)2(CHI2)]，具有 Cr(III) )-CHI2 部分。在 TMEDA 存在下，CHI2 发生亲核攻击，生成两性离子物质 [CrIII(OSi(O tBu)3)2(tmeda-CHI)][I]。筛选了配合物 [Cr2Cl4(CHI)(thf)4] 和 [CrII/III2I2(OSi(O tBu)3)2(CHI2)] 诱导苯甲醛单卤代烯烃化的能力。值得注意的是，这两种配合物都促进了烯化，[Cr2Cl4(CHI)(thf)4] 实现了与 Takai 原始混合物相同的 E 选择性。然而，复合物 [CrII/III2I2(OSi(O tBu)3)2(CHI2)]，
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