Tricyclic Quinoline derivatives from Intramolecular Cyclization of Benzylidene Malonic Derivatives

What is it about?

Quinolines are very important compounds due to their numerous biological and pharmacological applications. This article describes the synthesis of new tricyclic quinoline derivatives via intramolecular cyclization of malonic benzylidene derivatives. The malonic benzylidene derivatives 2a-c have been obtained by condensation of N-substituted aldehydes 1a-c with malononitrile or ethyl cyanoacetate. These latter have been cyclized by reflux in DMF to give the compounds 3a-f. The structures of the compounds have been determined by 1H and 13C NMR spectroscopy, and High-Resolution Mass Spectrometry (HRMS) analysis. Two of the synthesized compounds have been identified and confirmed by X-ray crystallography.

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Photo by Ronald Langeveld on Unsplash

Photo by Ronald Langeveld on Unsplash

Why is it important?

A number of protocols for the synthesis of the quinoline ring have been reported, which can be modified to produce various substituted quinolines. Common used methods are the classical syntheses such as the Skraup, Doebner-Von Miller, Pfitzinger, Friedlander, Conrad- Limpach and Combes synthesis. Here in this work, the synthesis of new tricyclic quinoline derivatives was done by intramolecular cyclization of malonic benzylidene derivatives.

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