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

Zhou, Jiao‐Long; Ye, Mengchun; Sun, Xiu‐Li; Tang, Yong

doi:10.1016/j.tet.2009.06.071

Cited by 16 publications

(7 citation statements)

References 73 publications

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“…11 TOX/Cu(II) was also efficient for the intramolecular Friedel−Crafts alkylation reaction, and up to 90% ee could be obtained with heterogenic TOX ligand 2e (Scheme 8). 39 Recently, we developed a type of benzyl substituted TOX, ligands 11 (Scheme 9), which are solids at room temperature and much more convenient to handle than pasty i Pr-TOX. Ligands 11 were very efficient, and in the reactions of indoles with alkylidene malonates, the catalyst loading (11a/Cu-(OTf) 2 ) can be reduced to 0.5 mol % without loss of enantioselectivity.…”

Section: Asymmetric Reactions Of Alkylidene Malonates and Related Tra...mentioning

confidence: 99%

Side Arm Strategy for Catalyst Design: Modifying Bisoxazolines for Remote Control of Enantioselection and Related

2014

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In asymmetric catalysis, the remote control of enantioselection is usually difficult due to the long distance communication between the chiral center of the catalyst and the reactive site of the substrate. The development of efficient and highly enantioselective catalysts for such reactions is of great importance and highly desirable. The stereocontrol over an asymmetric reaction is a delicate process (ca. 3.0 kcal/mol difference in transition states can lead to >99/1 enantiomeric selectivity at room temperature), it therefore requires fine-tuning on the electronic nature of the central metal together with a precisely created cavity to accommodate the substrates and reagents. We envision that a solution is the design of new catalysts by finding an easy and efficient way to tune the electronic properties, the chiral space, and the shape of the catalytic site. Since an extra coordination group in the organometallic complex could not only alter the microenvironment around the metal center in a three-dimensional manner but also tune the electronic properties of the metal center, about 10 years ago, we introduced a side arm strategy for ligand/catalyst design. This Account describes our efforts toward this goal. Based on this side arm strategy, we have developed two series of ligands based on the bisoxazoline framework; namely, trisoxazoline (TOX) ligands and side armed bisoxazoline (SaBOX). The "side arms" are shown to play multiple roles in different cases, for example, as a ligating group, a steric group, or a directing group, which are dependent on the metal and the functionality at the side arm. Metal catalysts based on these ligands have proven to be highly efficient for a number of asymmetric transformations, including Friedel-Crafts reaction, Kinugasa reaction, Nazarov reaction, 1,2-Stevens rearrangement, Cannizzaro reaction, and cyclopropanation. In comparison with the parent BOX ligands, the metal catalysts based on these TOX and SaBOX ligands usually exhibit higher efficiency and diastereo- and enantioselectivity with better impurity tolerance and stability. Moreover, in several TOX-metal complex catalyzed reactions such as Friedel-Crafts reaction and [3 + 2] cycloaddition, stereoselectivity could be switched based on reaction conditions. These ligands were particularly prominent in the remote controls of enantioselection such as the conjugate additions to alkylidene malonates and ring-opening/cyclization cascades of cyclopropanes, for which high stereoselectivity is usually difficult to achieve due to the poor chiral communication. The works by us and other groups have demonstrated that the side arm strategy can be employed as a general principle for ligand and catalyst design and should not be limited to the BOX scaffolds and the reactions described in this Account. Wide application of the new strategy in organometallic homogeneous catalysis can be anticipated.

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Section: Asymmetric Reactions Of Alkylidene Malonates and Related Tra...mentioning

confidence: 99%

Side Arm Strategy for Catalyst Design: Modifying Bisoxazolines for Remote Control of Enantioselection and Related

2014

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“…Silanol groups are condensed and they form the polymer siloxane, this act creates an amorphous material consisting of spherical particles consisting of SiO 4 groups irregularly. Applications of silica gel are due to its surface characters and depend on the distribution and nature of hydroxyl groups on the surface [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] . Various techniques such as NMR, IR, Raman, and chemical experiments have been used to determine the silica structure.…”

Section: Siomentioning

confidence: 99%

“…The results obtained show that OH groups present in silica surface. This compound was studied in various mechanisms such as phenols nitration, de-protection of tri methyl silyl ether, the epoxy ring opening, oxidation of alcohol, aldol ketone condensation and the other reactions as a catalyst [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] .…”

Section: Siomentioning

confidence: 99%

Investigation of Friedel‐Crafts Alkylation in the Presence of Supported Sulfonic Acid on Silica Gel

Kiasat

Karimi-Cheshmeali

Soleymani

et al. 2011

Journal of Chemistry

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From the Reaction between cellulose and chloro sulfonic acid was prepared sulfuric acid cellulose composition as a new solid acid. The solid acid supported on silica gel and then as an effective catalyst in Friedel-Crafts alkylation of alcohols and aromatic compounds was used. The reaction progress was controlled using thin layer chromatography and the reaction products were analyzed using IR spectroscopy devise. The results show this new catalyst is effective in the friedel crafts alkylation and C-C bond formation was done in short time with very good yields.

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“…[28] The side arms can play roles as a ligating group, a steric group, as well as a directing group to remote control enantioselection in various catalytic asymmetric reactions. [29][30][31][32][33][34][35][36][37][38][39][40][41][42] With these considerations in mind, we designed and synthesized herein several chiral diaminopyrrolidine derived N4 ligands with and without a chiral sidearm. These ligands coordinate with ferrous iron to afford the corresponding chiral non-heme iron complexes.…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, Tang et al introduced a side arm strategy for designing chiral ligands and their corresponding complexes, and various chiral ligands based on the bisoxazoline framework including trisoxazoline and side armed bisoxazoline were synthesized based on this strategy . The side arms can play roles as a ligating group, a steric group, as well as a directing group to remote control enantioselection in various catalytic asymmetric reactions …”

Section: Introductionmentioning

confidence: 99%

Asymmetric Epoxidation of α,β‐Unsaturated Ketones Catalyzed by Chiral Iron Complexes of (R,R)‐3,4‐Diaminopyrrolidine Derived N4‐Ligands with Camphorsulfonyl Sidearms

Zhang

et al. 2020

Asian J Org Chem

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

Cited by 16 publications

References 73 publications

Side Arm Strategy for Catalyst Design: Modifying Bisoxazolines for Remote Control of Enantioselection and Related

Side Arm Strategy for Catalyst Design: Modifying Bisoxazolines for Remote Control of Enantioselection and Related

Investigation of Friedel‐Crafts Alkylation in the Presence of Supported Sulfonic Acid on Silica Gel

Asymmetric Epoxidation of α,β‐Unsaturated Ketones Catalyzed by Chiral Iron Complexes of (R,R)‐3,4‐Diaminopyrrolidine Derived N4‐Ligands with Camphorsulfonyl Sidearms

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