Atroposelective Kinetic Resolution of 8<i>H</i>-Indeno[1,2-<i>c</i>]thiophen-8-ols via Pd-Catalyzed C–C Bond Cleavage Reaction

Xi, Junwei; Yang, Hao; Li, Lin; Zhang, Xue; Li, Chunyu; Gu, Zhenhua

doi:10.1021/acs.orglett.2c00642

Cited by 15 publications

(18 citation statements)

References 62 publications

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“…In this reaction, a silylated phosphoramidite L9 gave the highest selectivity (Scheme ). In the presence of 0.50 equiv of aryl bromides, an excellent enantioselectivity of the ring-opening product 31 could be achieved, while with 0.60 equiv of aryl bromides, 96–99% ee of the unchanged alcohols could be isolated. The palladium-catalyzed C–C bond cleavage of the racemic biphenyl compound (±)- 32 is a parallel kinetic resolution process: both ( S a )- 33 and ( R a )- 34 were accomplished in excellent enantioselectivity.…”

Section: Asymmetric Ring-opening Through C–c Bond Cleavagementioning

confidence: 99%

Transition Metal-Catalyzed Biaryl Atropisomer Synthesis via a Torsional Strain Promoted Ring-Opening Reaction

2022

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Conspectus Arising from the restricted rotation of a single bond caused by steric or electronic effects, atropisomerism is one of the few fundamental categories for molecules to manifest their three-dimensional characters into which axially chiral biaryl compounds fall. Despite the widespread occurrence of axially chiral skeletons in natural products, bioactive molecules, and chiral ligands/organocatalysts, catalytic asymmetric methods for the synthesis of these structures still lag behind demand. Major challenges for the preparation of these chiral biaryls include accessing highly sterically hindered variants while controlling the stereoselectivity. A couple of useful strategies have emerged for the direct asymmetric synthesis of these molecules in the last two decades. Recently, we have engaged in catalytic asymmetric synthesis of biaryl atropisomers via transition metal catalysis, including asymmetric ring-openings of dibenzo cyclic compounds. During these studies, we serendipitously discovered that the two substituents adjacent to the axis cause these dibenzo cyclic molecules to be distorted to minimize steric repulsion. The distorted compounds display higher reactivity in the ring-opening reactions than the non-distorted molecules. In other words, torsional strain can promote a ring-opening reaction. On the basis of this concept, we have successfully realized the catalytic asymmetric ring-opening reaction of cyclic diaryliodoniums, dibenzo silanes, and 9H-fluoren-9-ols, which delivered several differently substituted ortho tetra-substituted biaryl atropisomers in high enantioselectivity. The torsional strain not only activates the substrates toward ring-opening under mild conditions but also changes the chemoselectivity of bond-breaking events. In the palladium-catalyzed carboxylation of S-aryl dibenzothiophenium, the torsional strain inversed the bond selectivity from exocyclic C–S bond cleavage to the ring-opening reaction. In this Account, we summarize our studies on copper-, rhodium-, or palladium-catalyzed asymmetric ring-opening reactions of dibenzo cyclic compounds as a useful collection of methods for the straightforward preparation of ortho tetra-substituted biaryl atropisomers with high enantiopurity on the basis of the above-mentioned torsional strain-promoted ring-opening coupling strategy. In the last part, the torsional strain energies are also discussed with the aid of density functional theory (DFT) calculations.

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Section: Asymmetric Ring-opening Through C–c Bond Cleavagementioning

confidence: 99%

Transition Metal-Catalyzed Biaryl Atropisomer Synthesis via a Torsional Strain Promoted Ring-Opening Reaction

2022

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“…Next, we subjected thiazole 3d to dioxidation with an excess of m -chloroperbenzoic acid and obtained the corresponding thiazole S , S -dioxide 11 in 81% yield after 12 h (Scheme ). It is important to note that the double bond of 3d did not react with m- CPBA even after 12 h, probably due to the extended conjugation obtained.…”

Section: Resultsmentioning

confidence: 98%

Chemo- and Stereoselective Synthesis of Substituted Thiazoles from tert-Alcohols Bearing Alkene and Alkyne Groups with Alkaline Earth Catalysts

Yaragorla

Latha

2022

ACS Omega

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We report here that thioamides can distinguish C–C double bonds and C–C triple bonds chemoselectively when subjected to a reaction with pent-1-en-4-yn-3-ol derivatives in the presence of Ca(OTf) 2 . This protocol offers a fast, efficient, and high-yielding synthesis of functionalized thiazoles. Interestingly, this reaction offers a time-dependent formation of kinetic and thermodynamic products. The products showed stereoselectivity concerning the alkene geometry. Further, we extended this protocol to synthesize oxazoles from propargyl alcohols and ibuprofen (NSAID) was converted into amide and then subjected to oxazole formation with tert -propargyl alcohols.

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“…These substrates displayed either low enantioselectivity or poor reactivity in our previous work (3 f-3 m). [14] A potential AIE unit, tetraphenylethene moiety, was efficiently incorporated to the axially chiral compound (3 n). Double arylation was achieved in high yields and diastereoselectivities with the bisbromides as the limiting agent (3 o-3 q).…”

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From Peripheral Stereogenic Center to Axial Chirality: Synthesis of 3‐Arylthiophene Atropisomers

Hong

et al. 2022

Adv Synth Catal

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A practical synthesis of axially chiral biaryls via chirality transfer from peripheral stereogenic carbon centers is reported. In contrast to the traditional aromatization process of a non-aromatic structure with ipso stereogenic centers, this method is based on a Pd-catalyzed carbon-carbon bond cleavage/ring-opening reaction of optically active 8H-indenothiophen-8-ols with an achiral ligand, enabling synthesis of highly functionalized 3-arylthiophene atropisomers in high enantioselectivity.

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Atroposelective Kinetic Resolution of 8H-Indeno[1,2-c]thiophen-8-ols via Pd-Catalyzed C–C Bond Cleavage Reaction

Cited by 15 publications

References 62 publications

Transition Metal-Catalyzed Biaryl Atropisomer Synthesis via a Torsional Strain Promoted Ring-Opening Reaction

Transition Metal-Catalyzed Biaryl Atropisomer Synthesis via a Torsional Strain Promoted Ring-Opening Reaction

Chemo- and Stereoselective Synthesis of Substituted Thiazoles from tert-Alcohols Bearing Alkene and Alkyne Groups with Alkaline Earth Catalysts

From Peripheral Stereogenic Center to Axial Chirality: Synthesis of 3‐Arylthiophene Atropisomers

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