Highly enantioselective construction of CF3-bearing all-carbon quaternary stereocenters: Chiral spiro-fused bisoxazoline ligands with 1,1′-binaphthyl sidearm for asymmetric Michael-type Friedel-Crafts reaction

Bao, Robert Li‐Yuan; Shi, Lei; Fu, Kang

doi:10.1016/j.cclet.2021.10.062

Cited by 9 publications

(8 citation statements)

References 45 publications

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Section: Conjugate Addition To Electrophilic Cc Bondsmentioning

confidence: 99%

“…Recently, Shi et al developed a spiro-fused BOX chiral ligand L27 -based catalyst system, containing Ni(ClO 4 ) 2 ·6H 2 O/ L27 complex, for the asymmetric Michael-type F–C reaction of indoles 93 with β-CF 3 -β-disubstituted nitroalkenes 94 . 51 The design of ligand L27 was based on incorporating rigid spirocyclic units, which limited its flexibility and the related complex (Ni(ClO 4 ) 2 ·6H 2 O /L27 , which, in turn, allowed a better stereocontrol. Moreover, the C 2 symmetry of ligand L27 limited the number of possible transition states, and their chiral binaphthyl side arms can create a deep chiral pocket, which, in turn, increases confinement of β-disubstituted nitroalkene 94 for enhanced enantioselectivity.…”

Section: Conjugate Addition To Electrophilic C=c Bondsmentioning

confidence: 99%

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Recent Advances in the Catalytic Asymmetric Friedel–Crafts Reactions of Indoles

2022

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Functionalized chiral indole derivatives are privileged and versatile organic frameworks encountered in numerous pharmaceutically active agents and biologically active natural products. The catalytic asymmetric Friedel–Crafts reaction of indoles, catalyzed by chiral metal complexes or chiral organocatalysts, is one of the most powerful and atom-economical approaches to access optically active indole derivatives. Consequently, a wide range of electrophilic partners including α,β-unsaturated ketones, esters, amides, imines, β,γ-unsaturated α-keto- and α-ketiminoesters, ketimines, nitroalkenes, and many others have been successfully employed to achieve a plethora of functionalized chiral indole moieties. In particular, strategies for C–H functionalization in the phenyl of indoles require incorporation of a directing or blocking group in the phenyl or azole ring of indole. The discovery of chiral catalysts which can control enantiodiscrimination has gained a great deal of attention in recent years. This review will provide an updated account on the application of the asymmetric Friedel–Crafts reaction of indoles in the synthesis of diverse chiral indole derivatives, covering the timeframe from 2011 to today.

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Section: Conjugate Addition To Electrophilic Cc Bondsmentioning

confidence: 99%

Section: Conjugate Addition To Electrophilic C=c Bondsmentioning

confidence: 99%

Recent Advances in the Catalytic Asymmetric Friedel–Crafts Reactions of Indoles

2022

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“…[ 2 ] This can be understood, on one hand, by the existence of such skeleton in natural products with biological activities, exemplified by 6β‐acetoxy‐13α‐hydroxyhaplopan‐7‐one, [ 3 ] cornutin L, [ 4 ] sterpurene, [ 5 ] illudiolone, [ 6 ] and atlanticone C [ 7 ] (Figure 1), and on the other hand, by the potential of using these molecules for downstream studies in chemical biology and medicinal chemistry. Unfortunately, synthesizing this skeleton faces several challenges such as overcoming ring‐strain of forming four‐membered rings [ 8 ] and steric congestion of building quaternary stereocenters [ 9 ] and control of the stereochemistry.…”

Section: Background and Originality Contentmentioning

confidence: 99%

Catalytic Enantioselective Construction of 6‐4 Ring‐Junction All‐Carbon Stereocenters and Mechanistic Insights

Wang

et al. 2022

Chin. J. Chem.

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Comprehensive Summary Developing reactions for the synthesis of 6‐6‐4 and 6‐4 carbocyclic scaffolds with a chiral quaternary center at the bridgehead position is highly desired, considering the existence of such skeletons in natural products with biological activities and the potential of using these molecules for downstream studies in chemical biology and medicinal chemistry. Report here is accessing these target skeletons with high chemo‐, regio‐ and enantio‐selectivities through Pd(II)/chiral N,N’‐disulfonyl bisimidazoline (Bim) ligand‐catalyzed asymmetric reaction of yne‐allenones and arylboronic acids. Realization of 6‐6‐4 skeleton with a ring‐junction all‐carbon stereocenter is a one‐step process while synthesizing 6‐4 skeleton is a two‐step process, which begins with intramolecular [2 + 2] reaction of allenes with alkynes, followed by Pd‐catalyzed asymmetric addition of arylboronic acids to cyclic enones generated in the first step. Noteworthy is that chiral Bim ligand as a C2‐symmetric N,N’‐bidentateanionic ligand, designed by us, in coordinating with Pd catalyst was first applied to catalyze asymmetric 1,4‐conjugate addition reaction with the high catalytic performance (the reaction can be carried out in air). DFT calculations have been applied to understand how these reactions take place, the origins of enantioselectivity, and relative reactivities of different substrates.

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“…In 2022, Shi et al disclosed the synthesis of a novel type of chiral spiro-fused bisoxazoline ligands possessing a deep chiral pocket. 35 Among them, chiral ligand 11 employed at 10 mol% of catalyst loading was found to be highly efficient when combined with 11 mol% of Ni(ClO 4 ) 2 ·(H 2 O) 6 as precatalyst to promote enantioselective Michael-type Friedel–Crafts reaction between indoles and β-trifluoromethyl-β-disubstituted nitroalkenes (R 2 = CF 3 ). As presented in Scheme 16, the reaction carried out at 85 or 100 °C in toluene as solvent resulted in the formation of the corresponding chiral indole derivatives bearing a trifluoromethylated all-carbon quaternary stereocenter with moderate to quantitative yields (45–99%) and generally high enantioselectivities (78–>99% ee).…”

Section: Conjugate Additions To Nitroalkenesmentioning

confidence: 99%