Publisher Summary This chapter outlines the progress in quinoxaline chemistry. The preparation of numerous reduced quinoxalines and more unusual derivatives of this type include quinoxaline spirohydantoins and quinoxaline spiroindoles. Quinoxaline is resistant to nitration under mild conditions. Preparation of quinoxalines from o-diamines and o-nitrosoamines and that of quinoxalines using α-amino acid intermediates are discussed. The classical synthesis of quinoxalines involves the condensation of an aromatic o-diamine and an α-dicarbonyl compound. The properties and reactions of some α-substituted quinoxalines—such as tautomerism of 2-aminoquinoxaline, reactivity of α-methyl groups, and quaternization of 2-amino- and 2-acetamido-quinoxaline—are described along with the reactions of quinoxaline N-oxides and reformulation of glucazidone and quinoxaline analogs of pteroic acid. The physical properties of ultraviolet absorption spectra, infrared absorption spectra, and ionization properties are discussed and the effect of substituent on basic strength in ionization constants of quinoxalines is illustrated.