9-Thiourea Cinchona alkaloid supported on mesoporous silica as a highly enantioselective, recyclable heterogeneous asymmetric catalyst

A readily recycled and regenerated heterogeneous catalyst of 9-thiourea epi-quinine supported on mesoporous silica exhibits enhanced enantioselectivity (up to 99.2%) in the asymmetric Friedel-Crafts reaction of imines with indoles.     

吲哚与亚胺的Friedel-Crafts反应的研究进展

由于吲哚类化合物具有许多生物特性等优点,在众多天然产物和相应的具有生物活性的化合物中起重要的骨架构筑作用,其合成方法的研究格外令人注目.近年来,关于吲哚与亚胺在催化剂作用下发生Friedel-Crafts反应来制备3-取代吲哚甲胺衍生物的报道剧增.对近年来吲哚与亚胺Friedel-Crafts反应的研究情况进行了综述.     

Enantioselective synthesis of (3-indolyl)glycine derivatives via asymmetric Friedel-Crafts reaction between indoles and glyoxylate imines

Chiral phosphoric acid-catalyzed enantioselective Friedel-Crafts reaction of indoles with ethyl glyoxylate imines was developed. With 10 mol % of the catalyst, the Friedel-Crafts reactions between a wide range of indoles and imines have been carried out, affording optically active (3-indolyl)glycine derivatives with excellent yields and high enantioselectivities (up to 87% ee).     

SPINOL-derived phosphoric acids: synthesis and application in enantioselective Friedel-Crafts reaction of indoles with imines

A new class of chiral phosphoric acids with spirobiindane as scaffold were conveniently synthesized from (S)-1,1'-spirobiindane-7,7'-diol ((S)-SPINOL) and employed to catalyze the asymmetric Friedel-Crafts reaction of indoles with imines to afford 3-indolyl methanamines. High yields (68-97%) and excellent enantioselectivities (up to 99% ee) were obtained.     

Enantioselective Friedel-Crafts reaction of indoles with carbonyl compounds catalyzed by bifunctional cinchona alkaloids

In this communication, we report an efficient asymmetric Friedel-Crafts reaction that, unprecedently, is applicable to a wide range of both indoles and carbonyls. The use of a readily accessible catalyst in combination with a high enantioselectivity that is insensitive to reaction concentration, temperature, air, and moisture should allow this reaction to provide useful enantioselective access to new chiral indole derivatives. [reaction: see text]     

Chiral sulfonimide as a Brønsted acid organocatalyst for asymmetric Friedel-Crafts alkylation of indoles with imines

Binaphthyl-based chiral sulfonimide (CSI) is demonstrated for the first time to be an efficient, strong Br?nsted acid in asymmetric organocatalysis. A series of CSIs were synthesized and screened in the asymmetric Friedel-Crafts alkylation of indoles with imines. Good to excellent yields and enantioselectivities have been achieved. It was proved that it was crucial to wash the CSI catalyst with HCl before use.     

Trisoxazoline/Cu(II)-catalyzed asymmetric intramolecular Friedel-Crafts alkylation reaction of indoles

Intramolecular Friedel-Crafts alkylation reaction of indoles catalyzed by trisoxazoline/copper(II) is described. This annulation provides an easy access to polycyclic indole derivatives with up to 90% ee in up to 99% yield.     

Enantioselective Friedel-Crafts alkylation of indoles with nitroalkenes catalyzed by a bis(oxazoline)-Cu(II) complex

The catalytic enantioselective Friedel-Crafts reaction of indole with trans-β-nitrostyrene is reported in the presence of copper triflate-bisoxazoline complexes. The reaction furnished nitroalkylated indoles in excellent yields (up to 95%) and high enantioselectivities up to an 86% ee.     

Highly regioselective Friedel-Crafts alkylation of indoles with α,β-unsaturated N-acylbenzotriazoles

The Friedel-Crafts alkylation rather than acylation of indoles was realized with α,β-unsaturated acylbenzotriazoles catalyzed by samarium(III) iodide under reflux in anhydrous THF. The reaction was highly regioselective, and a series of new 3-substituted indole derivatives were obtained in moderate to good yields with the potential to be further transformed into various indole derivatives due to the presence of active acylbenzotriazole moiety.     

Convenient synthesis of bis(indolyl)alkanes by dithiocarbohydrazone Schiff base/Zn(ClO_4 )_2 6H_2 O catalyzed Friedel–Crafts reaction of indoles with imines

A new, convenient and excellent yield procedure for the preparation of bis(indolyl)methanes(BIMs) by Friedel–Crafts reaction of indoles with imines in the presence of dithiocarbohydrazone Schiff base/ Zn(ClO4)2 6H2 O as a highly stable, effective and readily available catalyst is described. Moderate to good yields(up to 99% yield) were obtained with both substrates for imine derivatives. This procedure is simple, practical and economic.     

Asymmetric synthesis of β2-tryptophan analogues via Friedel-Crafts alkylation of indoles with a chiral nitroacrylate

The asymmetric Friedel-Crafts alkylation of various indoles with a chiral nitroacrylate provides optically active β-tryptophan analogues after reduction of the nitro group and removal of the chiral auxiliary. This reaction generally occurs in good yield and high diastereoselectivity (up to 90:10).     

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.     

Regiodivergent Intramolecular Nucleophilic Addition of Ketimines for the Diverse Synthesis of Azacycles

Azacycles such as indoles and tetrahydroquinolines are privileged structures in drug development. Reported here is an unprecedented regiodivergent intramolecular nucleophilic addition reaction of imines as a flexible approach to access N‐functionalized indoles and tetrahydroquinolines, by the control of reaction at the N‐terminus and C‐terminus, respectively. Using ketimines derived from 2‐(2‐nitroethyl)anilines with isatins or α‐ketoesters, the regioselective N‐attack reaction gives N‐functionalized indoles, while the catalytic enantioselective C‐attack reaction affords chiral tetrahydroquinolines featuring an α‐tetrasubstituted stereocenter. Mechanistic studies reveal that hydrogen‐bonding interactions may greatly facilitate such unusual N‐attack reactions of imines. The utility of this protocol is highlighted by the catalytic enantioselective formal synthesis of (?)‐psychotrimine, and the construction of various fused aza‐heterocycles.     

有机催化吲哚碳环上的不对称Friedel⁃Crafts烷基化反应

将金鸡纳碱衍生物双功能催化剂用于有机催化羟基吲哚与靛红的不对称Friedel-Crafts反应, 筛选出最佳反应条件: 催化剂为5%(摩尔分数)6′-脱甲基奎尼丁(1b), 溶剂为四氢呋喃, 反应温度 0 ℃. 以67%~91%的产率和最高达97%的对映选择性获得了苯环上取代的羟基烷基化产品. 拓宽了该反应的催化剂类型和底物范围.     

Asymmetric Friedel-Crafts alkylations of indoles with nitroalkenes catalyzed by Zn(II)-bisoxazoline complexes

[reaction: see text] A novel asymmetric Friedel-Crafts alkylation of indoles with nitroalkenes catalyzed by Zn(II)-bisoxazoline complexes has been developed. The nitroalkylated indoles are synthesized in excellent yields and high enantioselectivities (up to 90% ee). The effects of ligand structure, metal salt, and solvent on the reaction are discussed. The substrates of the reaction can be aromatic, heteroaromatic, and even aliphatic nitroalkenes. The high reactivity and selectivity of the reaction are presumptively attributed to the activation and asymmetric induction of chiral Lewis acids coordinated by nitroalkene substrates through a 1,3-metal bonding model.     

Catalytic enantioselective Friedel-Crafts/Michael addition reactions of indoles to ethenetricarboxylates

[reaction: see text] The Friedel-Crafts reaction is an important reaction for the formation of new C-C bonds. Recently, catalytic enantioselective Friedel-Crafts reaction of alkylidene malonates has been reported. However, the substituents in alkylidene malonates are limited. To explore new substituents such as carboxyl and carbonyl groups, catalytic enantioselective Friedel-Crafts reactions of reactive ethenetricarboxylates and acyl-substituted methylenemalonates 1 were investigated. The reaction of 1 with indoles in the presence of catalytic amounts of chiral bisoxazoline copper(II) complex (10%) in THF at room temperature gave alkylated products in high yields and up to 95% ee. The enantioselectivity can be explained by the secondary orbital interaction on approach of indole to the less hindered side of the 1-Cu(II)-ligand complex.     

Enantioselective synthesis of tryptophan derivatives by a tandem Friedel-Crafts conjugate addition/asymmetric protonation reaction

The tandem Friedel-Crafts conjugate addition/asymmetric protonation reaction between 2-substituted indoles and methyl 2-acetamidoacrylate is reported. The reaction is catalyzed by (R)-3,3'-dibromo-BINOL in the presence of stoichiometric SnCl(4), and is the first example of a tandem conjugate addition/asymmetric protonation reaction using a BINOL·SnCl(4) complex as the catalyst. A range of indoles furnished synthetic tryptophan derivatives in good yields and high levels of enantioselectivity, even on a preparative scale. The convergent nature of this transformation should lend itself to the preparation of unnatural tryptophan derivatives for use in a broad array of synthetic and biological applications.     

Catalytic asymmetric Pictet-Spengler-type reaction for the synthesis of optically active indolo[3,4-cd][1]benzazepines

A new strategy has been introduced to develop a catalytic asymmetric Pictet-Spengler-type reaction by replacing the aldehyde with an imine. A range of 4-(2-aminoaryl)indoles smoothly undergo the chiral phosphoric acid catalyzed asymmetric Pictet-Spengler-type reaction with imines at room temperature to give structurally diverse indolo[3,4-cd][1]benzazepines in good to excellent yields and ee.     

A new type of bis(sulfonamide)-diamine ligand for a Cu(OTf)2-catalyzed asymmetric Friedel-Crafts alkylation reaction of indoles with nitroalkenes

Chiral bis(sulfonamide)-diamine served as new type of ligand for a Cu(OTf)(2)-catalyzed asymmetric Friedel-Crafts alkylation reaction of indoles with nitroalkenes. The desired products were obtained with up to 99% yield and 97% ee.     

Enantioselective Friedel-Crafts alkylation of indoles with nitroalkenes catalyzed by bifunctional tridentate bis(oxazoline)-Zn(II) complex

[reaction: see text] A more practical and efficient catalytic asymmetric Friedel-Crafts alkylation of indoles with nitroalkenes using bifunctional tridentate bis(oxazoline)-Zn(OTf)(2) as catalyst has been developed. Various types of the nitroalkylated indoles were obtained in excellent yields (85-99%) and high enantioselectivities (up to 98% ee).