Fritsch, L., Moura e Silva, S., Baptista, L.A. et al. (2 more authors) (2025) Synthesis of quinoline liquid crystals by inverse electron demand Diels-Alder cycloaddition. Tetrahedron, 183. 134722. ISSN 0040-4020
Abstract
Tetrahydroquinolines (THQ) cycloadducts, as well as their oxidation to the corresponding quinolines are reported. THQs were achieved through the Inverse Electron Demand [4 + 2]-Diels–Alder (IEDDA) cycloaddition. The [4 + 2]-IEDDA cycloadducts were obtained through a three-component reaction involving aromatic aldehydes, amines and pyrano dienophile, in the presence of TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperydine-1-oxyl), trifluoroacetic acid and acetonitrile, in low yields <40 %. Theoretical studies were complimentary performed to analyze the chemical reactivity, regio- and stereoselectivity of the IEDDA cycloaddition. The preference for the formation of the THQs cycloadducts was dictated by frontier orbital molecular (FOMs) LUMO of 2-azadieno and HOMO of the dienophile. Oxidation of the THQs with DDQ yielded quinolines in high yields >90 %. The thermal behavior of the THQs and quinolines was studied using DSC and POM techniques. The final quinolines exhibited an amorphous appearance with vitreous, glossy, and brittle characteristics. Through POM studies only one quinoline displayed stable liquid crystal behavior with a glass transition temperature (Tg) and glassy nematic mesophase at room temperature was assigned, without no thermal decomposition detected after cycles of heating and cooling.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Keywords: | Aza-Diels-Alder; THQ cycloadducts; Quinolines; Liquid crystals and DFT calculation |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Physics and Astronomy (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 03 Jun 2025 15:42 |
Last Modified: | 03 Jun 2025 15:42 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.tet.2025.134722 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:227219 |