Glycerol and Q-Tubes: Green Catalyst and Technique for Synthesis of Polyfunctionally Substituted Heteroaromatics and Anilines

Abstract

The role of glycerol as a green bio-based solvent, reactant, and/or a catalyst in the synthesis of novel heterocycles, under pressure, is studied. Synthesis of novel quinolines in good yields using a new modified Skraup synthesis, utilizing glycerol and pressure Q-tubes, is demonstrated. Novel aniline trimers are prepared using glycerol, and substituted anilines under pressure, in acidic medium and water. Glycerol was employed as a catalyst and a green solvent in the synthesis of novel pyridazines 13a–c. The mechanisms of the reactions and the catalytic effect of glycerol in protic and aprotic media are fully discussed. The structures of the synthesized compounds were determined via X-ray crystallography and spectroscopic methods.

Quinoline‐derivatives as privileged scaffolds for medicinal and pharmaceutical chemists: A comprehensive review

“…Elnagdi and coworkers reported the modified skraup reaction using aniline, sulphuric acid, glycerol, and water in pressure Q‐tubes without the use of oxidizing agents. Glycerol was used as catalyst and solvent that improved the reaction yield and reduced reaction time (Almarzouq & Elnagdi, 2019). Naima et al reported the reaction (Scheme 1) in which they used excess glycerol, concentrated sulfuric acid and iodine as an oxidizing agent at 110°C temperature for 1 h then increased the temperature to 170°C for another hour.…”

A simple continuous reaction for the synthesis of quinoline compounds

“…Among these methods, the classic and common methods are the Friedlander, Skraup, Doebner-von Miller and Combes reactions. [5][6][7][8][9] Although these methods have great general applicability and show good conversion for various types of quinoline compounds, the conditions required for their reaction are relatively harsh and the reaction process is complicated and have long steps. The reaction usually requires strong acids, oxidants and other hazardous reagents which adversely affect the environment-friendly chemistry and atom economy.…”