Regioselective preparation and NMR spectroscopy study of 2-chloro-4-ethoxy-quinoline for the synthesis of 2-((3-aminopropyl)amino)quinolin-4(1H )-one,Magnetic Resonance in Chemistry

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Regioselective preparation and NMR spectroscopy study of 2-chloro-4-ethoxy-quinoline for the synthesis of 2-((3-aminopropyl)amino)quinolin-4(1H )-one
Magnetic Resonance in Chemistry ( IF 1.9 ) Pub Date : 2019-12-23 , DOI: 10.1002/mrc.4980
Pedro Henrique Vasconcelos Vontobel ₁ , Rodrigo Dos Santos Fuscaldo ₁ , Francisco Paulo Dos Santos ₁ , Jessie Sobieski da Costa ₁

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Herein, we describe the C4-ethoxylation of 2,4-dichloroquinoline to prepare 2-chloro-4-ethoxy-quinoline (3), which is a prominent intermediate used for the synthesis of 2-substituted quinolones. To achieve this goal we studied different conditions for the reaction between 2,4-dichloroquinoline and sodium ethoxide. We discovered that the use of 18-crown-6 ether as an additive and DMF as the reaction solvent allowed us to obtain the desired product 3 in very good yield and selectivity. In addition, a definitive distinction between the C2 and C4 ethoxylation products was achieved using 1 H-15 N HMBC. Compound 3 is an intermediate used for the synthesis of 2-((3-aminopropyl)amino)quinolin-4(1H)-one (5), which displays peculiar behavior during 1 H NMR analysis, such as the broadening of the H8 singlet and unexpected deuteration at the C8-position. Effort has been dedicated to understand these findings.

中文翻译：

2-氯-4-乙氧基-喹啉用于合成2-((3-氨基丙基)氨基)喹啉-4(1H)-酮的区域选择性制备和核磁共振波谱研究

在本文中，我们描述了 2,4-二氯喹啉的 C4-乙氧基化以制备 2-氯-4-乙氧基-喹啉 (3)，这是用于合成 2-取代喹诺酮类的主要中间体。为了实现这一目标，我们研究了 2,4-二氯喹啉和乙醇钠之间反应的不同条件。我们发现使用 18-crown-6 醚作为添加剂和 DMF 作为反应溶剂使我们能够以非常好的收率和选择性获得所需的产物 3。此外，使用 1 H-15 N HMBC 可以明确区分 C2 和 C4 乙氧基化产物。化合物 3 是用于合成 2-((3-aminopropyl)amino)quinolin-4(1H)-one (5) 的中间体，它在 1 H NMR 分析中表现出特殊的行为，例如 H8 单线态的展宽和在 C8 位置意外的氘化。

更新日期：2019-12-23

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