- Remarkably Efficient Iridium Catalysts for Directed C(sp2)-H and C(sp3)-H Borylation of Diverse Classes of Substrates
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Here we describe the discovery of a new class of C-H borylation catalysts and their use for regioselective C-H borylation of aromatic, heteroaromatic, and aliphatic systems. The new catalysts have Ir-C(thienyl) or Ir-C(furyl) anionic ligands instead of the diamine-type neutral chelating ligands used in the standard C-H borylation conditions. It is reported that the employment of these newly discovered catalysts show excellent reactivity and ortho-selectivity for diverse classes of aromatic substrates with high isolated yields. Moreover, the catalysts proved to be efficient for a wide number of aliphatic substrates for selective C(sp3)-H bond borylations. Heterocyclic molecules are selectively borylated using the inherently elevated reactivity of the C-H bonds. A number of late-stage C-H functionalization have been described using the same catalysts. Furthermore, we show that one of the catalysts could be used even in open air for the C(sp2)-H and C(sp3)-H borylations enabling the method more general. Preliminary mechanistic studies suggest that the active catalytic intermediate is the Ir(bis)boryl complex, and the attached ligand acts as bidentate ligand. Collectively, this study underlines the discovery of new class of C-H borylation catalysts that should find wide application in the context of C-H functionalization chemistry.
- Chattopadhyay, Buddhadeb,Hassan, Mirja Md Mahamudul,Hoque, Md Emdadul
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supporting information
p. 5022 - 5037
(2021/05/04)
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- Highly enantioselective intramolecular cyanoamidation: (+)-horsfiline, (-)-coerulescine, and (-)-esermethole
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(Figure Presented) The first asymmetric cyanoamidation with synthetically useful enantioselectivlty (ee up to 99%) to produce 3,3-disubstltuted oxindoles Is reported. Palladium catalysts with chi ral phosphoramldite ligands activate the cyanoformamide C-CN bond, which is subsequently functionalized with a tethered alkene to give all-carbon quaternary stereocenters. The use of the N,N-(i-Pr)2 derivative of octahydro-MonoPhos allowed the production of oxindoles with high enantioselectivlties. Cyanoformamides bearing free N-H groups are now tolerated, potentially allowing protecting-group-free synthesis. Oxindole products of cyanoamidation are rapidly transformed into (+)-horsfiline, (-)-coerulescine, and (-)-esermethole.
- Reddy, Venkata Jaganmohan,Douglas, Christopher J.
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supporting information; experimental part
p. 952 - 955
(2010/06/15)
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- Catalytic C-CN activation and asymmetric cyanoamidation of alkenes: Total syntheses of (+)-horsfiline, (-)-coerulescine, and (-)-esermethole
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The detailed study of Pd-catalyzed asymmetric cyanoamidation is reported. Excellent enantioselectivities are attributed to a chiral phosphosphoramidite ligand synthesized in one step from the commercially available materials. Cyanoamidation substrates are easy to prepare from the corresponding anilines. The 3,3-disubstituted oxindole products bear all-carbon quaternary stereocenters and contain a nitrile and an amide, which are valuable functional handles for the synthesis of many indole-containing natural products. Cyanoamidation tolerates free N-H groups, as demonstrated by the successful use of cyanoamidation in the syntheses of (+)-horsfiline and (-)-coerulescine.
- Reddy, Venkata Jaganmohan,Douglas, Christopher J.
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experimental part
p. 4719 - 4729
(2010/08/06)
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- Axial chirality control during suzuki-miyaura cross-coupling reactions: The tert-Butylsulfinyl group as an efficient chiral auxiliary
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An efficient route to a new family of axially chiral biaryl ligands by a Suzuki-Miyaura cross-coupling reaction between ortho,ortho'-disubstituted aryl iodides bearing in ortho position a tert-butyl or p-tolylsulfinyl group and ortho-substituted phenyl boronic acids or esters is described. The comparison between the t-BuSO and p-TolSO groups as chiral controllers is reported. The modularity of the approach is demonstrated by the preparation of a variety of enantiopure axially chiral mixed S/N and S/P ligands.
- Colobert, Francoise,Valdivia, Victoria,Choppin, Sabine,Leroux, Frederic R.,Fernandez, Inmaculada,Alvarez, Eleuterio,Khiar, Noureddine
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supporting information; experimental part
p. 5130 - 5133
(2009/12/28)
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