Enantioselective Friedel-Crafts Alkylation Of Indoles Research Articles

Enantioselective Friedel-Crafts alkylation of indoles with trifluoropyruvates catalyzed by chiral Cu(II) complex bearing binaphthyl-proline hybrid ligands

A mild and efficient catalyst system for asymmetric Friedel-Crafts alkylation of indoles with trifluoropyruvates was reported. The chiral ligands took the advantages of both the proline and the binaphthyl moieties, and the in situ prepared Cu(II) catalyst showed good substrate tolerance in the reactions. Indoles bearing different substituents could be tolerated, and the desired products could be obtained in up 99 % yields and up to 98 % ee. Especially, the reactions could be carried out in gram scale without the loss of stereoselectivity, and some of products were able to achieve 99 % ee after simple crystallization.

Cofactor Binding Dynamics Influence the Catalytic Activity and Selectivity of an Artificial Metalloenzyme.

We present an artificial metalloenzyme based on the transcriptional regulator LmrR that exhibits dynamics involving the positioning of its abiological metal cofactor. The position of the cofactor, in turn, was found to be related to the preferred catalytic reactivity, which is either the enantioselective Friedel–Crafts alkylation of indoles with β-substituted enones or the tandem Friedel–Crafts alkylation/enantioselective protonation of indoles with α-substituted enones. The artificial metalloenzyme could be specialized for one of these catalytic reactions introducing a single mutation in the protein. The relation between cofactor dynamics and activity and selectivity in catalysis has not been described for natural enzymes and, to date, appears to be particular for artificial metalloenzymes.

Efficient Catalytic Kinetic Resolution of Spiro-epoxyoxindoles with Concomitant Asymmetric Friedel-Crafts Alkylation of Indoles.

An efficient process involving the catalytic kinetic resolution of racemic spiro-epoxyoxindoles with the simultaneous enantioselective Friedel-Crafts alkylation of indoles has been realized using a chiral phosphoric acid catalyst. The reaction provides two useful intermediates in high yields and excellent enantioselectivities. Performing the catalysis on a gram scale led to (R)-3-(3-indolyl)-oxindole-3-methanol, which was used in the asymmetric formal total synthesis of (+)-gliocladin C. Notably, the enantiomers (S)-3-(3-indolyl)-oxindole-3-methanol can be obtained easily by the reaction of the resolved spiro-epoxyoxindole with indole.

Design and Applications of N-tert-Butyl Sulfinyl Squaramide Catalysts.

A new chiral HBD system, N-tert-butyl sulfinyl squaramide, was designed and synthesized. The core N-tert-butyl sulfinyl squaramide with an 1-aminoindan-2-ol skeleton was found to be an efficient catalyst in the enantioselective Friedel-Crafts alkylation of indoles and acyl phosphonates.

Cu(I)-Catalyzed Enantioselective Friedel-Crafts Alkylation of Indoles with 2-Aryl-N-sulfonylaziridines as Alkylating Agents.

A highly enantioselective Friedel-Crafts alkylation of indoles with N-sulfonylaziridines as alkylating agents has been developed by utilizing the complex of Cu(CH3CN)4BF4/(S)-Segphos as a catalyst. A range of optically active tryptamine derivatives are obtained in good to excellent yields and enantioselectivities (up to >99% ee) via a kinetic resolution process.

Supramolecular Assembly of Artificial Metalloenzymes Based on the Dimeric Protein LmrR as Promiscuous Scaffold.

Supramolecular anchoring of transition metal complexes to a protein scaffold is an attractive approach to the construction of artificial metalloenzymes since this is conveniently achieved by self-assembly. Here, we report a novel design for supramolecular artificial metalloenzymes that exploits the promiscuity of the central hydrophobic cavity of the transcription factor Lactococcal multidrug resistance Regulator (LmrR) as a generic binding site for planar coordination complexes that do not provide specific protein binding interactions. The success of this approach is manifested in the excellent enantioselectivities that are achieved in the Cu(II) catalyzed enantioselective Friedel-Crafts alkylation of indoles.

Dianhydrohexitols: new tools for organocatalysis. Application in enantioselective Friedel-Crafts alkylation of indoles with nitroalkenes

A series of hydrogen bonding organocatalysts was synthesized from dianhydrohexitol and was used for the first time in organocatalysis for Friedel-Crafts alkylation of indoles with nitroalkenes. Moderate yields and enantioselectivities were achieved.

NMR Spectroscopic Characterization and DFT Calculations of Zirconium(IV)-3,3′-Br2–BINOLate and Related Complexes Used in an Enantioselective Friedel–Crafts Alkylation of Indoles with α,β-Unsaturated Ketones

Experimental and theoretical studies on the structure of several complexes based on (R)-3,3'-Br(2)-BINOL ligand and group (IV) metals used as catalysts in an enantioselective Friedel-Crafts alkylation of indoles with α,β-unsaturated ketones have been carried out. NMR spectroscopic studies of these catalysts have been performed, which suggested that at room temperature the catalysts would form a monomeric structure in the case of Ti(IV) and a dimeric structure in the cases of Zr(IV) and Hf(IV). Density functional theory (DFT) calculations clearly corroborate the conclusions of these experimental spectroscopic studies. The dimeric structure with a doubly bridged motif [Zr(IV)(2)(μ-(R)-3,3'-Br(2)-BINOL)(2)] where each binaphthol ligand acts as bridge between the metal centers (Novak's model) is more stable than the dimeric structure with a doubly bridged motif [Zr(IV)(2)(μ-O(t)Bu)(2)] where the tert-butoxide groups act as bridging ligands (Kobayashi's model). The scope of the Friedel-Crafts alkylation with regard to the indole structure has been studied. Finally a plausible mechanism for the Friedel-Crafts reaction and a stereomodel for the mode of action of the catalyst that explain the observed stereochemistry of the reaction products have been proposed.

Catalytic Enantioselective Friedel-Crafts Alkylation of Indoles with Fumarate Derivatives in the Presence of Chiral Palladium Complexes

The catalytic enantioselective Friedel–Crafts alkylation reaction promoted by chiral palladium complexes is described. The treatment of indoles with fumarate derivatives under the mild reaction conditions afforded the corresponding Friedel–Crafts alkylation adducts with high enantioselectivities (up to 91% ee).

Enantioselective Friedel–Crafts alkylation of indoles with 2-enoylpyridine-N-oxides catalyzed by glucoBOX-Cu(ii) complex

The glucosamine derived glucoBOX-Cu(II) complex was found to be a unique catalytic system for enantioselective Friedel-Crafts alkylation of indoles with 2-enoylpyridine-1-oxides. A large number of 3-alkylated indole derivatives were prepared using 5 mol% glucoBOX-Cu(II) complex in excellent yields with high enantioselectivity up to 99% ee.

Asymmetric Friedel–Crafts alkylation of indoles with 3-nitro-2H-chromenes catalyzed by diphenylamine-linked bis(oxazoline) and bis(thiazoline) Zn(II) complexes

An efficient diastereo- and enantioselective Friedel-Crafts alkylation of indoles with 3-nitro-2H-chromenes catalyzed by diphenylamine-linked bis(oxazoline) and bis(thiazoline) Zn(II) complexes has been developed. This asymmetric Friedel-Crafts alkylation led to medicinally privileged indolyl(nitro)chromans in good yields with high enantioselectivities (up to 95% ee) and diastereoselectivities under mild reaction conditions.

Catalytic Enantioselective Friedel-Crafts Alkylation of Indoles with β,γ-Unsaturated α-Keto Phosphonates in the Presence of Chiral Palladium Complexes

The catalytic enantioselective Friedel-Crafts alkylation reaction promoted by chiral palladium complexes is described. The treatment of indoles with β,γ-unsaturated α-keto phosphonates under the mild reaction conditions afforded the corresponding Friedel-Crafts alkylation adducts with excellent enantioselectivities (up to 99% ee).

Synthesis of Tridentate Ligands Based on Chiral Diamines and Their Application to Enantioselective Friedel‐Crafts Alkylation of Indoles with Nitroalkenes

AbstractA new type of chiral tridentate ligands were prepared and their Zn complexes were examined for the asymmetric Friedel‐Crafts alkylation of indoles with nitroalkenes, which gave rise to good yields and moderate enantioselectivities.

Copper-Catalyzed Enantioselective Friedel-Crafts Alkylation of Indoles

Friedel-Crafts alkylation of indole derivatives with α,β-unsaturated carbonyl compounds has been extensively developed due to the importance of indoles as building blocks in natural products and pharmaceutical agents. Despite the many contributions already in the literature, challenges still remain in developing highly efficient chiral catalysts for the Friedel-Crafts alkylation between indole and alkylidenemalonate. The authors reported the studies of hetero­arylidenemalonate-derived bis(oxazoline) ligands, such as 1, and their copper(II) complexes in the highly efficient and enantioselective Friedel-Crafts alkylation of indoles and alkylidenemalonates.

Chiral Brønsted Acid Directed Iron‐Catalyzed Enantioselective Friedel–Crafts Alkylation of Indoles with β‐Aryl α′‐Hydroxy Enones

A cooperative catalytic system established by the combination of an iron salt and a chiral Brønsted acid has proven to be effective in the asymmetric Friedel-Crafts alkylation of indoles with beta-aryl alpha'-hydroxy enones. Good to excellent yields and enatioselectivities were observed for a variety of alpha'-hydroxy enones and indoles, particularly for the beta-aryl alpha'-hydroxy enones bearing an electron-withdrawing group at the para position of the phenyl ring (up to 90 % yield and 91 % ee). The proton of the chiral Brønsted acid, the Lewis acid activation site, as well as the inherent basic site for the hydrogen-bonding interaction of the Brønsted acid are responsible for the high catalytic activities and enantioselectivities of the title reaction. A possible reaction mechanism was proposed. The key catalytic species in the catalytic system, the phosphate salt of Fe(III), which was thought to be responsible for the high activity and good enantioselectivity, was then confirmed by ESIMS studies.

Enantioselective Friedel-Crafts Alkylation of Indoles with Aromatic α,β-Unsaturated Aldehydes Catalyzed by Diphenylprolinol Silyl Ether

A catalytic enantioselective Friedel-Crafts alkylation of indoles with aromatic α,β-unsaturated aldehydes has been developed. The process is promoted by (S)-diphenylprolinol trimethyl silyl ether to afford, after sodium borohydride mediated reduction, 3-indolyl-3-phenylpropanols in high enantioselectivities and good yields.

CaSH Organocatalysis: Enantioselective Friedel-Crafts Alkylation of Indoles with α,β-Unsaturated Aldehydes

Enantioselective Friedel-Crafts alkylation of indole with α,β-unsaturated aldehyde was catalyzed by camphor sulfonyl hydrazine (CaSH) with good enantioselectivity (81-88%).

Enantioselective Friedel-Crafts Alkylation of Indoles with Alkylidene Malonates

Enantioselective Friedel-Crafts Alkylation of Indoles with Alkylidene Malonates

New Ligands for Copper-Catalyzed Friedel-Crafts Reactions of Indoles

A new class of bis(imidazoline) ligands, related to the pybox family, are used for the Cu-catalyzed enantioselective Friedel-Crafts alkylation of indoles. Both enantiomers of product can be synthesized depending on the ligand, which can also be used as chiral Brønsted acids in combination with achiral acids.

Enantioselective Friedel-Crafts Alkylation of Indoles with Nitroalkenes

Enantioselective Friedel-Crafts Alkylation of Indoles with Nitroalkenes