Quinoline derivatives are prevalent in a variety of pharmacologically active synthetic and natural compounds. Friedländer prepared quinoline in 1882 by the condensation of o-aminobenzaldehyde with acetaldehyde in the presence of sodium hydroxide. Quinolines have antiseptic, antipyretic, and antiperiodic properties and are used as antimalarials and for preparing other antimalarial drugs. The discovery of chloroquine, the most famous drug containing this scaffold, resulted in control and treatment of malaria for decades. Quinoline and its derivatives are widely used as fungicides, biocides, antibiotics, alkaloids, dyes, rubber chemicals, and flavoring agents. Additional industrial applications include their use as corrosion inhibitors, preservatives, and as solvents for resins and terpenes, and in transition-metal complex catalysis for uniform polymerization and luminescence chemistry. They are also used in manufacturing oil soluble dyes, food colorants, pharmaceuticals, pH indicators and other organic compounds. Quinoline is a catabolite of tryptophan, a fundamental structure in some antihypertensive agents such as the peripheral vasodilators prazosin and doxazosin.