scholarly journals Exploiting the Chiral Ligands of Bis(imidazolinyl)- and Bis(oxazolinyl)thiophenes—Synthesis and Application in Cu-Catalyzed Friedel–Crafts Asymmetric Alkylation

Molecules ◽  
2021 ◽  
Vol 26 (23) ◽  
pp. 7408
Author(s):  
Mohammad Shahidul Islam ◽  
Abdullah Saleh Alammari ◽  
Assem Barakat ◽  
Saeed Alshahrani ◽  
Matti Haukka ◽  
...  
Keyword(s):  
Dicarboxylic Acid ◽  
Optical Purity ◽  
Chemical Yield ◽  
Amino Alcohols ◽  
Asymmetric Induction ◽  
Chiral Ligands ◽  
Tridentate Ligand ◽  
Asymmetric Alkylation

Five new C2-symmetric chiral ligands of 2,5-bis(imidazolinyl)thiophene (L1–L3) and 2,5-bis(oxazolinyl)thiophene (L4 and L5) were synthesized from thiophene-2,5-dicarboxylic acid (1) with enantiopure amino alcohols (4a–c) in excellent optical purity and chemical yield. The utility of these new chiral ligands for Friedel–Crafts asymmetric alkylation was explored. Subsequently, the optimized tridentate ligand L5 and Cu(OTf)2 catalyst (15 mol%) in toluene for 48 h promoted Friedel–Crafts asymmetric alkylation in moderate to good yields (up to 76%) and with good enantioselectivity (up to 81% ee). The bis(oxazolinyl)thiophene ligands were more potent than bis(imidazolinyl)thiophene analogues for the asymmetric induction of the Friedel–Crafts asymmetric alkylation.

Axially Chiral 3,3'-Bi(1-benzothiophene)-2,2'-dicarboxylic Acid and Its Derivatives

2003 ◽  
Vol 68 (5) ◽  
pp. 1020-1038 ◽  
Author(s):  
Marie Mézlová ◽  
Hana Petříčková ◽  
Petr Maloň ◽  
Václav Kozmík ◽  
Jiří Svoboda
Keyword(s):  
Dicarboxylic Acid ◽  
Fractional Crystallization ◽  
Absolute Configuration ◽  
Optical Purity ◽  
Chiral Ligands ◽  
X Ray ◽  
Enantioselective Reduction ◽  
X Ray Crystallography ◽  
Axially Chiral

Ullmann dimerization of substituted methyl 3-X-1-benzothiophene-2-carboxylates 1-7 (X = Cl, Br) gave rise to the corresponding dimeric 3,3'-bi(1-benzothiophene) esters 8-13. Resolution of the title acid 20 by fractional crystallization of its mono- and bisquininium salt afforded pure (R)- and (S)-enantiomers, the optical purity and absolute configuration of which was confirmed by CD spectrometry and by X-ray crystallography. Ullmann dimerization of chiral oxazolines 23 and 24 derived from 2 proceeded without any diastereodifferentiation. Reduction of (R)- and (S)-20 afforded the corresponding (R)- and (S)-diols 29, which served as chiral ligands in a model enantioselective reduction of acetophenone. (R)- and (S)-1-phenylethan-1-ol were formed in 28 and 29% e.e., respectively.

New chiral tridentate ligands for asymmetric catalysis

2006 ◽  
Vol 78 (2) ◽  
pp. 311-320 ◽  
Author(s):  
Kevin Murtagh ◽  
Brian A. Sweetman ◽  
Patrick J. Guiry
Keyword(s):  
Asymmetric Catalysis ◽  
High Performance ◽  
Aromatic Aldehydes ◽  
Asymmetric Induction ◽  
Tridentate Ligand ◽  
Coupling Reactions ◽  
Tridentate Ligands ◽  
Molecular Complexation ◽  
Cross Coupling Reactions ◽  
Moderate Yield

The synthesis of new tridentate, isoquinoline-derived ligands, involving successive Suzuki cross-coupling reactions, is described. We were able to resolve 1-[3-(2-hydroxy-phenyl)-isoquinolin-1-yl]-naphthalen-2-ol via molecular complexation with N-benzylcinchonidinium chloride, whereas 1,3-bis(2-hydroxy-naphthalen-1-yl)-isoquinoline was resolved by chromatographic separation of its epimeric camphorsulfonates. Their barrier to rotation about the central biaryl axis was evaluated via racemization studies. Application of enantiopure 1,3-bis(2-hydroxynaphthalen-1-yl)-isoquinoline in the addition of diethylzinc to aldehydes proceeded in moderate yield but without asymmetric induction. A new tridentate ligand, 4-tert-butyl-2-chloro-6-[1-(2-hydroxymethyl-naphthalen-1-yl)-isoquinolin-3-yl]-phenol, was prepared in good yield and resolved by semipreparative high-performance liquid chromatography (HPLC). Its application in the addition of diethylzinc to a range of aromatic aldehydes proceeded in near perfect enantioselectivities at low ligand loadings of 1 mol %.

ChemInform Abstract: Stereoselective Syntheses of Ephedrine and Related 2-Amino Alcohols of High Optical Purity from Protected Cyanohydrins.

ChemInform ◽  
1990 ◽  
Vol 21 (51) ◽  
Author(s):  
W. R. JACKSON ◽  
H. A. JACOBS ◽  
B. R. MATTHEWS ◽  
G. S. JAYATILAKE ◽  
K. G. WATSON
Keyword(s):  
Optical Purity ◽  
Amino Alcohols ◽  
High Optical Purity ◽  
Stereoselective Syntheses

Enantioselective Transfer Reaction of Phenyl to Aldehydes Using LProline- Derived Amino Alcohols as Chiral Ligands

2014 ◽  
Vol 11 (5) ◽  
pp. 356-360 ◽  
Author(s):  
Yongmin Liu ◽  
Rongcheng Bo ◽  
Nan Wu ◽  
Yuehua Qiao ◽  
Yong Li ◽  
...  
Keyword(s):  
Transfer Reaction ◽  
Amino Alcohols ◽  
Chiral Ligands

Total synthesis and establishment of the absolute stereochemistry of (+)-mostueine. Addition of chiral nucleophiles to 3,4-dihydro-2-methyl-9-(p-toluenesulfonyl)-β-carbolinium iodide

1992 ◽  
Vol 70 (12) ◽  
pp. 2922-2928 ◽  
Author(s):  
Allan W. Rey ◽  
Walter A. Szarek ◽  
David B. MacLean
Keyword(s):  
Total Synthesis ◽  
Indole Alkaloid ◽  
Optical Purity ◽  
Ring System ◽  
Asymmetric Induction ◽  
Iminium Salt ◽  
High Optical Purity ◽  
The Absolute ◽  
Absolute Stereochemistry ◽  
Mediated Reduction

A highly convergent synthesis of the pentacyclic indole alkaloid (+)-mostueine (1) is described. The key step involved the coupling of the dianion derived from (1′S)-3-(1′-hydroxyethyl)-4-methylpyridine (4) with the iminium salt 3,4-dihydro-2-methyl-9-(p-toluenesulfonyl)-β-carbolinium iodide (3). Low asymmetric induction (15% de) at the C-1 position of the β-carboline ring system (C-3 of mostueine) was obtained. The nonfermenting baker's yeast-mediated reduction of 3-acetyl-4-methylpyridine provided the hydroxyethylpyridine component in acceptable yield (67%) and high optical purity (99.0% ee). This synthesis of 1 has established that the absolute stereochemistry of mostueine is (3S, 19R).

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