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ABSTRACT: Herein we report a highly enantioselective synthesis of polycyclic indoles and pyrroles with up to 99% ee by an iridium-catalytic system comprised of commercially available iridium precursor and readily accessible ligand. Investigation of the reaction mechanism led to the discovery of an unprecedented dearomatized spiro-intermediate and its in-situ migration phenomenon. The new reaction mode features the switch of the sub-stituent from the C-3 position of indole to the C-2 position (C-2 position to C-3 position in the case of pyrrole) without loss of the enantiomeric purity, providing a novel concept in designing asymmetric construction of enantiopure polycyclic indoles and pyrroles.
Journal of the American Chemical Society 05/2013; · 9.91 Impact Factor
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ABSTRACT: This paper describes a combined theoretical and experimental investigation into the acid-catalyzed migration of spiroindolenines to the corresponding fused cyclic products. It is suggested that the "three-center-two-electron"-type transition state is the crucial reason accounting for the highly stereoselective phenomenon. Further studies demonstrated that the electronic property of the migratory group as well as the ring size may have a major influence on the reaction profile of the migration process. Some predictions based on the computational results were supported by additional experiments.
The Journal of Organic Chemistry 04/2013; · 4.45 Impact Factor
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ABSTRACT: A highly efficient synthesis of spiro-tetrahydroquinolines (up to 99% yield) has been realized via cascade hydrogenative dearomatization of quinoline and intramolecular aza-Friedel-Crafts alkylation reaction.
Organic Letters 03/2013; · 5.86 Impact Factor
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ABSTRACT: Chiral phosphoric acid works together with Hoveyda-Grubbs II catalyst enabling highly efficient synthesis of enantioenriched tetrahydro-β-carboline (up to 95% yield, 90% ee) through an olefin isomerization/Pictet-Spengler cascade reaction via sequential catalysis.
Organic & Biomolecular Chemistry 01/2013; · 3.70 Impact Factor
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ABSTRACT: Enantioselective Pd(II)-catalyzed direct coupling of aminomethyl ferrocene derivatives with boronic acids was realized. With commercially available Boc-L-Val-OH as a ligand, planar chiral ferrocenes could be synthesized in 14-81% yields with up to 99% ee under mild conditions.
Journal of the American Chemical Society 12/2012; · 9.91 Impact Factor
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ABSTRACT: This Review summarizes the development of catalytic asymmetric dearomatization (CADA) reactions. The CADA reactions discussed herein include oxidative dearomatization reactions, dearomatization by Diels-Alder and related reactions, the alkylative dearomatization of electron-rich arenes, transition-metal-catalyzed dearomatization reactions, cascade sequences involving asymmetric dearomatization as the key step, and nucleophilic dearomatization reactions of pyridinium derivatives. Asymmetric dearomatization reactions with chiral auxiliaries and catalytic asymmetric reactions of dearomatized substrates are also briefly introduced. This Review intends to provide a concept for catalytic asymmetric dearomatization.
Angewandte Chemie International Edition 12/2012; · 13.45 Impact Factor
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ABSTRACT: Highly diastereoselective and enantioselective desymmetrization of alpha-substituted cyclohexadienones via NHC-catalyzed intramolecular Stetter reaction was realized. Amino-indanol derived triazolium salt (J) bearing a C6F5 group was found to be the optimal catalyst precursor in the intramolecular Stetter reaction furnishing tricyclic substrates bearing multi stereocenters in up to 96% yield and >99% ee.
The Journal of Organic Chemistry 11/2012; · 4.45 Impact Factor
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ABSTRACT: Chiral phosphoric acid worked together with Hoveyda-Grubbs II catalyst enabling highly efficient synthesis of enantioenriched tetrahydro-β-carbolines (up to 98% yield, 99% ee) through a ring-closing metathesis/isomerization/Pictet-Spengler cascade reaction via sequential catalysis.
Organic Letters 09/2012; 14(19):5022-5. · 5.86 Impact Factor
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ABSTRACT: Enantioselective construction of pyrroloindolines via chiral phosphoric acid catalyzed cascade Michael addition-cyclization of tryptamines has been realized. With 5 mol % of chiral phosphoric acid, enantioenriched pyrroloindoline derivatives were obtained in good yields and enantioselectivity (up to 95% yield and 83% ee) from readily available tryptamines and enones.
Organic Letters 08/2012; 14(17):4588-90. · 5.86 Impact Factor
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ABSTRACT: Copper(I)-catalyzed dearomative arylation and vinylation of 2-substituted tryptophols were realized with a subsequent cyclization reaction. The cascade dearomatization sequence provided versatile furoindoline derivatives with two quaternary carbon centers in good to excellent yields.
Organic Letters 08/2012; 14(17):4525-7. · 5.86 Impact Factor
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ABSTRACT: Lewis acid-catalyzed cascade dearomatization of N-substituted tryptophols via Michael addition reaction was developed. The generality of the method has been demonstrated by the synthesis of versatile furoindoline derivatives with a quaternary carbon center in good yields.
Organic & Biomolecular Chemistry 07/2012; 10(35):7177-83. · 3.70 Impact Factor
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ABSTRACT: Dearomatization of an indole via palladium(0)-catalyzed cross-coupling reaction has been realized. With readily available triphenylphosphine as ligand, various spiroindolenine derivatives have been obtained in good to excellent yields, and enantioselective control is also feasible with chiral ligands.
Organic Letters 07/2012; · 5.86 Impact Factor
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ABSTRACT: A formal [4 + 2] cycloaddition of 2,3-disubstituted indoles with vinyl methyl ketone was realized in the presence of a catalytic amount of quinine-derived primary amine and pentafluorobenzoic acid. This method provides bridged-ring indoline scaffolds containing two quaternary carbon centers with excellent yields and enantioselectivity (up to 98% yield and 98% ee).
Organic Letters 05/2012; 14(12):3040-3. · 5.86 Impact Factor
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ABSTRACT: Enantioselective desymmetrization of cyclohexadienones via a d-camphor-derived triazolium salt catalyzed intramolecular Stetter reaction was realized. With 10 mol% of camphor-derived triazolium salt E and 10 mol% of DIEA, various substituted cyclohexadienones proceeded through an intramolecular Stetter reaction, affording tricyclic products in moderate to good yields and excellent ee.
Chemical Communications 05/2012; · 6.17 Impact Factor
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ABSTRACT: An efficient iridium-catalyzed intramolecular Friedel-Crafts-type allylic alkylation reaction of phenols was developed, affording tetrahydroisoquinolines with moderate to excellent yields, enantioselectivity, and good regioselectivity.
Organic Letters 04/2012; · 5.86 Impact Factor
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ABSTRACT: Two steps can be better than one: An efficient synthesis of enantioenriched N-allylindoles by a one-pot Ir-catalyzed asymmetric allylic alkylation/oxidation reaction of indolines has been realized. The current method features high regioselectivity and enantioselectivity together with a broad range of indoles with varying electronic properties. The utility of this method was demonstrated by the synthesis of dihydropyrrolo[1,2-a]indole derivatives.
Angewandte Chemie International Edition 04/2012; 51(21):5183-7. · 13.45 Impact Factor
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ABSTRACT: Iridium-catalyzed asymmetric allylic amination of allylic carbonates with 2-allylanilines was realized. With a catalyst generated from 2 mol% of [Ir(dbcot)Cl](2) (dbcot = dibenzo[a,e]cyclooctatetraene) and 4 mol% of phosphoramidite ligand (L3), the amination products were obtained in up to 99% yield and 99% ee. Subjecting amination products to trifluoroacetyl protection and ring-closing-metathesis reaction provided an efficient synthesis of enantioenriched 2,5-dihydrobenzo[b]azepine derivatives.
Organic & Biomolecular Chemistry 03/2012; 10(30):5932-9. · 3.70 Impact Factor
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ABSTRACT: In recent years, Hantzsch esters and their related organic hydride donors have been widely utilized in biomimetic approaches of asymmetric transfer hydrogenation (ATH) reactions. Various compounds containing C=C, C=N and C=O unsaturated functionalities could be reduced in the presence of organocatalysts or transition metal complexes, affording versatile chiral building blocks in high yields and excellent enantioselectivities under mild conditions. In this critical review, recent advances in this area are summarized and classified according to unsaturated functional groups being reduced and catalytic systems employed (91 references).
Chemical Society Reviews 03/2012; 41(6):2498-518. · 28.76 Impact Factor
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ABSTRACT: A highly efficient tandem double Friedel-Crafts reaction between indoles and 2-formylbiphenyl derivatives by chiral N-triflyl phosphoramide was realized. Under mild conditions, various 9-(3-indolyl) fluorene derivatives have been obtained in good yield and up to 94% ee. Comparing to their corresponding chiral phosphoric acids, chiral N-triflyl phosphoramides catalyzed reactions led to products with opposite absolute configuration.
Organic & Biomolecular Chemistry 03/2012; 10(16):3202-9. · 3.70 Impact Factor
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ABSTRACT: A series of N-aryl phosphoramidite ligands has been synthesized and applied to iridium-catalyzed allylic alkylation reactions, offering high regio- and enantioselectivities for a wide variety of substrates. These ligands feature the synthetic convenience and good tolerance of the ortho-substituted cinnamyl carbonates. Mechanistic studies, including DFT calculations and X-ray crystallographic analyses of the (π-allyl)-Ir complexes, reveal that the active iridacycle is formed via C(sp(2))-H bond activation.
Journal of the American Chemical Society 02/2012; 134(10):4812-21. · 9.91 Impact Factor
