Synthesis of quinoline liquid crystals by inverse electron demand Diels-Alder cycloaddition

IF 2.1 3区化学 Q2 CHEMISTRY, ORGANIC

Tetrahedron Pub Date : 2025-05-13 DOI:10.1016/j.tet.2025.134722

Luma Fritsch , Sidnei Moura e Silva , Luis A. Baptista , Richard J. Mandle , Aloir A. Merlo

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引用次数: 0

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.

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反电子需求Diels-Alder环加成法合成喹啉液晶

报道了四氢喹啉（THQ）环加合物及其氧化生成相应的喹啉的过程。thq是通过逆电子需求[4 + 2]-Diels-Alder （IEDDA）环加成得到的。[4 + 2]-IEDDA环加合物是在TEMPOL（4-羟基-2,2,6,6-四甲基哌啶-1-氧基）、三氟乙酸和乙腈存在下，由芳香醛、胺和吡喃二酚三组分反应得到的，产率低至40%。对IEDDA环加成的化学反应性、区域选择性和立体选择性进行了理论分析。THQs环加合物的形成偏好由前沿轨道分子（FOMs） 2-氮杂二烯的LUMO和二亲化合物的HOMO决定。四氢呋喃醌与DDQ氧化得到喹啉，产率高达90%。采用DSC和POM技术研究了四氢醌和喹啉类化合物的热行为。最终的喹啉表现出玻璃状、有光泽和脆性的无定形外观。通过POM研究，只有一种喹啉表现出稳定的液晶行为，在室温下具有玻璃化转变温度（Tg）和玻璃状向列中间相，加热和冷却循环后未检测到热分解。

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来源期刊

Tetrahedron 化学-有机化学

CiteScore

3.90

自引率

4.80%

发文量

439

审稿时长

34 days

期刊介绍： Tetrahedron publishes full accounts of research having outstanding significance in the broad field of organic chemistry and its related disciplines, such as organic materials and bio-organic chemistry. Regular papers in Tetrahedron are expected to represent detailed accounts of an original study having substantially greater scope and details than that found in a communication, as published in Tetrahedron Letters. Tetrahedron also publishes thematic collections of papers as special issues and ''Reports'', commissioned in-depth reviews providing a comprehensive overview of a research area.