•Complexes of Y, La Sm, and Lu with a chiral tridentate amido-indenyl ligand.•X-ray single crystal structures of the complexes were obtained.•Structure-reactivity study of the complexes was done in cyanosilylation of ketones.•1H NMR spectral analysis used to probe the origin of the lack of enantioselectivity.The complexes of rare-earth metals (Y, La, Sm and Lu) with a chiral tridentate amido-fluorenyl ligand were synthesized and characterized. These complexes demonstrated high efficiency in catalyzing both the intramolecular hydroamination of non-activated olefins and the cyanosilylation of ketones under very mild conditions, however, with no enantiocontrol being achieved. 1H NMR monitoring of the reaction process suggests the weak coordination capacity of the fluorenyl moiety might be responsible for the lack of asymmetric inducing power of the chiral complexes in such transformations.Download high-res image (156KB)Download full-size image

The enantioselective intramolecular hydroamination of alkenes with free amines has been a touchstone reaction in the development of many new chiral rare-earth (RE) metal complexes. In this article, we describe the synthesis and characterization of four novel rare-earth metal (Y, Sm, Lu, Sc) complexes, featuring a tridentate carbon-linked amido-indenyl ligand with a shortened linker between the indene ring and the chiral diamine moiety, as compared to our previously developed structurally similar silicon-linked ligand. Despite the generally lower enantioselectivities obtained in the current work, the structure–activity analyses of these complexes based on X-ray crystallographic data could be useful for further development of highly efficient chiral rare-earth metal complexes for asymmetric synthesis.

An organocatalytic dearomative [3 + 2]-annulation of N-alkyl-3-alkylindoles with quinone monoketals is developed. The reaction provides a mild and straightforward way to various benzofuro[2,3-b]indolines of potential biological and pharmaceutical interest in moderate to good yields. Moreover, when 3-phenylindole, a problematic substrate in previous relevant studies, was used as the substrate under the otherwise same reaction conditions, a novel 1,2-shift of the phenyl group occurred followed by aromatization to provide 2,3-diaryl indoles useful for cancer therapy studies in moderate yields.

A new chiral silicon-linked tridentate amido-indenyl ligand was developed from indene and enantiopure 1,2-cyclohexanediamine. Its yttrium complex was synthesized, characterized and applied to efficiently catalyze the intramolecular hydroamination of non-activated olefins with up to 97% ee.

•Complexes of Y, Sm, Er and Yb with a tridentate amido-indenyl ligand were synthesized.•X-ray single crystal structures of the four complexes were obtained.•Structure-reactivity study of the complexes was done in intramolecular hydroamination.•Substrate scope study with various aminoalkenes was done with complexes of Y and Sm.The complexes of rare-earth metals (Y, Sm, Er and Yb) with a tridentate silicon-linked amido-indenyl ligand were synthesized and characterized. These complexes demonstrated high efficiency in catalyzing the intramolecular hydroamination of non-activated olefins under very mild conditions. Structure–reactivity relationship study revealed that the catalytic activities of these complexes decreased as the radii of the core metal ion decreased.Four novel rare-earth metal complexes (Y, Sm, Er, Yb) with linked tridentate amido-indenyl ligand was synthesized, characterized and applied to efficiently catalyze the intramolecular hydroamination of non-activated olefins.

cis-2,3-Disubstituted cyclopropane 1,1-diesters were found to be much more reactive than their corresponding trans-isomers in the AlCl3-promoted [3 + 2]-annulations with isothiocyanates. The reaction with the cis-cyclopropanes proceeded to completion within minutes, providing a variety of densely substituted diastereomerically pure 2-iminodihydrothiophenes in moderate to excellent yields.

A series of cis-2,3-disubstituted cyclopropane 1,1-diesters were examined in the AlCl3-promoted [3 + 2]-annulations with aldehydes. In this reaction, these cis-cyclopropanes displayed reactivities starkly different from their trans counterparts in terms of the high chemical yields (up to 98%) and provided the desired annulation products with excellent diastereomeric purity. This protocol provides a facile and highly stereoselective way to construct synthetically useful pentasubstituted tetrahydrofurans not easily accessible using other methods.

A three-component cascade reaction of salicylaldehyde, malononitrile/cyanoacetate and nitromethane catalysed by chiral tertiary amino-thioureas was developed, which leads to the production of highly functionalized 2-amino-4H-chromenes in good yields with good to excellent enantioselectivities.

An efficient bifunctional thiourea catalyzed addition–cyclization reaction of 2-naphthol with α,α-dicyanoolefins is realized under mild conditions to afford the corresponding naphthopyran derivatives in high yields and moderate enantioselectivities. Additionally, the development of an asymmetric three-component one-pot procedure for the synthesis of naphthopyran derivatives is also reported.(S)-3-Amino-1-phenyl-1H-benzo[f]chromene-2-carbonitrileC20H14N2OEe = 68%[α]D23.8=-5.2 (c 1.15, DMSO)Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-3-Amino-1-(4-bromophenyl)-1H-benzo[f]chromene-2-carbonitrileC20H13BrN2OEe = 71%[α]D27.7=-57.3 (c 0.93, DMSO)Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-3-Amino-1-(4-chlorophenyl)-1H-benzo[f]chromene-2-carbonitrileC20H13ClN2OEe = 84%[α]D24.8=-43.9 (c 0.7, DMSO)Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-3-Amino-1-(4-fluorophenyl)-1H-benzo[f]chromene-2-carbonitrileC20H13FN2OEe = 90%[α]D27.1=-2.8 (c 0.64, DMSO)Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-3-Amino-1-p-tolyl-1H-benzo[f]chromene-2-carbonitrileC21H16N2OEe = 79%[α]D24.3=-20.3 (c 3.05, DMSO)Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-3-Amino-1-(4-nitrophenyl)-1H-benzo[f]chromene-2-carbonitrileC20H13N3O3Ee = 65%[α]D27.4=-115.9 (c 0.4, DMSO)Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-3-Amino-1-(4-methoxyphenyl)-1H-benzo[f]chromene-2-carbonitrileC21H16N2O2Ee = 62%[α]D27.1=-19.5 (c 0.65, DMSO)Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-3-Amino-1-(2,4-dichlorophenyl)-1H-benzo[f]chromene-2-carbonitrileC20H13Cl2N2OEe = 56%[α]D26.8=+4.3 (c 0.73, DMSO)Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-3Amino-1-(3-fluorophenyl)-1H-benzo[f]chromene-2-carbonitrileC20H13FN2OEe = 70%[α]D27.5=-21.7 (c 0.62, DMSO)Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-3-Amino-1-(3-methoxyphenyl)-1H-benzo[f]chromene-2-carbonitrileC21H16N2O2Ee = 76%[α]D27.3=-6.6 (c 0.77, DMSO)Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-3-Amino-1-(2-chlorophenyl)-1H-benzo[f]chromene-2-carbonitrileC20H13ClN2OEe = 67%[α]D23.9=+28.5 (c 0.48, DMSO)Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-3-Amino-1-(3-chlorophenyl)-1H-benzo[f]chromene-2-carbonitrileC20H13ClN2OEe = 65%[α]D25.0=-18.4 (c 0.62, DMSO)Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-3-Amino-1-(furan-2-yl)-1H-benzo[f]chromene-2-carbonitrileC18H12N2O2Ee = 61%[α]D27.3=-45.5 (c 0.41, DMSO)Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-3-Amino-1-pentyl-1H-benzo[f]chromene-2-carbonitrileC19H20N2OEe = 57%[α]D27.8=+5.5 (c 0.64, CDCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-3-Amino-1-(4-fluorophenyl)-9-methoxy-1H-benzo[f]chromene-2-carbonitrileC21H15FN2O2Ee = 66%[α]D24.6=-51.35 (c 0.54, DMSO)Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-Ethyl 3-amino-1-(4-chlorophenyl)-1H-benzo[f]chromene-2-carboxylateC22H18ClNO2Ee = 34%[α]D12.7=+2.5 (c 0.33, CDCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S)

A novel bifunctional thiourea–tertiary-amine-catalyzed enantioselective Friedel–Craft-type addition reaction of 2-naphthol with β,γ-unsaturated α-keto ester was developed. Subsequent dehydration of the reaction adducts with a catalytic amount of concentrated H2SO4 in a one-pot fashion readily afforded a series of new optically active naphthopyran derivatives with moderate to good yields (up to 91%) and enantioselectivities (up to 90%).(S)-Methyl 1-phenyl-1H-benzo[f]chromene-3-carboxylateC21H16O3Ee = 87%[α]D22=-341.6 (c 0.50, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-Ethyl 1-phenyl-1H-benzo[f]chromene-3-carboxylateC22H18O3Ee = 82%[α]D20=-290.5 (c 0.50, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-Isopropyl 1-phenyl-1H-benzo[f]chromene-3-carboxylateC23H20O3Ee = 84%[α]D21=-182.9 (c 0.50, CHCl3);Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-Allyl 1-phenyl-1H-benzo[f]chromene-3-carboxylateC25H18O3Ee = 84%[α]D22=-112.2 (c 0.50, CHCl3);Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-Benzyl 1-phenyl-1H-benzo[f]chromene-3-carboxylateC27H20O3Ee = 78%[α]D22=-147.4 (c 0.50, CHCl3);Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-Methyl 1-(4-bromophenyl)-1H-benzo[f]chromene-3-carboxylateC21H20BrO3Ee = 87%[α]D22=-350.9 (c 0.50, CHCl3);Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-Methyl 1-(4-chlorophenyl)-1H-benzo[f]chromene-3-carboxylateC21H20ClO3Ee = 87%[α]D22=-369.7 (c 0.50, CHCl3);Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-Methyl 1-(4-fluorophenyl)-1H-benzo[f]chromene-3-carboxylateC21H20FO3Ee = 86%[α]D22=-290.6 (c 0.50, CHCl3);Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-Methyl 1-(4-ethoxyphenyl)-1H-benzo[f]chromene-3-carboxylateC23H20O4Ee = 72%[α]D22=-278.6 (c 0.50, CHCl3);Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-Methyl 1-(4-nitrophenyl)-1H-benzo[f]chromene-3-carboxylateC21H20NO5Ee = 90%[α]D22=-417.2 (c 0.50, CHCl3);Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-Methyl 1-(3-chlorophenyl)-1H-benzo[f]chromene-3-carboxylateC21H20ClO3Ee = 86%[α]D22=-341.0 (c 0.34, CHCl3);Source of chirality: asymmetric synthesisAbsolute configuration: (S)(R)-Methy 1-(2-bromophenyl)-1H-benzo[f]chromene-3-carboxylateC21H20BrO3Ee = 57%[α]D23=-102.3 (c 0.50, CHCl3);Source of chirality: asymmetric synthesisAbsolute configuration: (R)(S)-Methyl 1-(2,5-dimethoxyphenyl)-1H-benzo[f]chromene-3-carboxylateC23H20O5Ee = 60%[α]D21=-241.4 (c 0.50, CHCl3);Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-Methyl 8-bromo-1-phenyl-1H-benzo[f]chromene-3-carboxylateC21H20BrO3Ee = 86%[α]D23=-273.1 (c 0.50, CHCl3);Source of chirality: asymmetric synthesisAbsolute configuration: (S)(S)-Methyl 9-methoxy-1-phenyl-1H-benzo[f]chromene-3-carboxylateC22H18O4Ee = 82%[α]D23=-325.5 (c 0.50, CHCl3);Source of chirality: asymmetric synthesisAbsolute configuration: (S)

An unprecedented ring-opening mode of trans-2-aroyl-3-aryl-cyclopropane-1,1-dicarboxylates involving the cleavage of the C2C3 bond of the cyclopropane ring mediated by PCl5 was disclosed. This reaction provides an efficient metal-free way to functionalized stereodefined trisubstituted Z-vinyl chlorides in moderate to good yields. A tentative mechanism for the reaction has been proposed.

cis-2,3-Disubstituted cyclopropane 1,1-diesters were found to be much more reactive than their corresponding trans-isomers in the AlCl3-promoted [3 + 2]-annulations with isothiocyanates. The reaction with the cis-cyclopropanes proceeded to completion within minutes, providing a variety of densely substituted diastereomerically pure 2-iminodihydrothiophenes in moderate to excellent yields.

An organocatalytic dearomative [3 + 2]-annulation of N-alkyl-3-alkylindoles with quinone monoketals is developed. The reaction provides a mild and straightforward way to various benzofuro[2,3-b]indolines of potential biological and pharmaceutical interest in moderate to good yields. Moreover, when 3-phenylindole, a problematic substrate in previous relevant studies, was used as the substrate under the otherwise same reaction conditions, a novel 1,2-shift of the phenyl group occurred followed by aromatization to provide 2,3-diaryl indoles useful for cancer therapy studies in moderate yields.

A new chiral silicon-linked tridentate amido-indenyl ligand was developed from indene and enantiopure 1,2-cyclohexanediamine. Its yttrium complex was synthesized, characterized and applied to efficiently catalyze the intramolecular hydroamination of non-activated olefins with up to 97% ee.

A three-component cascade reaction of salicylaldehyde, malononitrile/cyanoacetate and nitromethane catalysed by chiral tertiary amino-thioureas was developed, which leads to the production of highly functionalized 2-amino-4H-chromenes in good yields with good to excellent enantioselectivities.