Highly enantioselective Friedel–Crafts alkylation of indole with electron deficient trans-β-nitroalkenes using Zn(II)–oxazoline–imidazoline catalysts
摘要:
The catalytic asymmetric Friedel-Crafts alkylation of indole with trans-beta-nitroolefins has been developed via the catalysis of Zn(II)-oxazoline-imidazoline complexes. The reaction furnished nitroalkylated indoles in excellent yields (up to 95%) and with high enantioselectivities (up to 99% ee). The effects of solvent, temperature, the metal-triflate, and the ligand structure on the reaction are discussed. The substrates of the reaction can be substituted aromatic nitroolifins. The higher reactivity and enantioselectivity of the reaction could be due to the activation and asymmetric induction of chiral Lewis acids coordinated by the nitroolefin through a 1,3-metal bonded intermediate. (C) 2013 Elsevier Ltd. All rights reserved.
Exploiting the Chiral Ligands of Bis(imidazolinyl)- and Bis(oxazolinyl)thiophenes—Synthesis and Application in Cu-Catalyzed Friedel–Crafts Asymmetric Alkylation
作者:Mohammad Shahidul Islam、Abdullah Saleh Alammari、Assem Barakat、Saeed Alshahrani、Matti Haukka、Abdullah Mohammed Al-Majid
DOI:10.3390/molecules26237408
日期:——
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
Enantioselective Friedel-Crafts alkylation of indole with nitroalkenes in the presence of bifunctional squaramide organocatalysts
作者:Esra Dündar、Cihangir Tanyeli
DOI:10.1016/j.tetlet.2021.153153
日期:2021.6
A series of chiral bifunctional quinine and 2-aminoDMAP based squaramide organocatalysts are evaluated in Friedel-Craftsalkylation of indoles with nitroolefins. These 3-substituted indole derivatives are synthesized in the presence of sterically encumbered tert-butyl squaramide/quinine with high enantioselectivity (up to >99% ee) and moderate chemical yields (up to 80%) by representing as chiral precursors