イソキノリン

化学的特性Isoquinoline is a colorless hygroscopic liquid at temperatures above its melting point with a heavy sweet balsamic, herbaceous odor. Impure samples can appear brownish, as is typical for nitrogen heterocycles. Isoquinoline is a slightly stronger base than quinoline (pKa=5.14) and has a larger dipole of 2.60D.

化学性质黄褐色の板状結晶，融点25?26℃，沸点242℃（99.35 kPa），水に不溶

High-temperature coal tar contains an average of 0.2% isoquinoline. It is separated by distillation from the lower-boiling quinoline and the higherboiling 2-methylquinoline of the quinoline base mixture. Further refining is based on the fact that isoquinoline, in contrast to quinoline and 2-methylquinoline, cannot be hydrated but can be crystallized at low temperature. Isoquinoline can by synthesized, for example, via the Bischler–Napieralski reaction by cyclodehydration of N-acyl derivatives of b-phenylethylamine with Lewis acids and subsequent dehydrogenation.

製造方法Bischler-Napieralski synthesis is used to synthesize isoquinolines. β-phenylethylamine is acylated, and then cyclodehydrated using phosphoryl chloride, phosphorus pentoxide or other Lewis acids to yield dihydroisoquinoline, which can be aromatized by dehydrogenation with palladium, for example in the synthesis of papaverine, a pharmacologically active isoquinoline alkaloid.Pictet-Spengler synthesis is another method of preparing isoquinolines. β-phenylethylamine reacts with an aldehyde to produce an imine, which undergoes acid-catalysed cyclization, resulting in the synthesis of the tetrahydroisoquinoline system. Again, tetrahydroisoquinoline can be aromatized by palladium dehydrogenation to produce an isoquinoline system.

純化方法Dry isoquinoline with Linde type 5A molecular sieves or Na2SO4 and fractionally distil at reduced pressure. Alternatively, it can be refluxed with, and distilled from, BaO. It is also purified by fractional crystallisation from the melt and distilled from zinc dust. It forms a phosphate (m 135o) and a picrate (m 223o), which are purified by crystallisation, and the free base can be recovered and distilled. [Packer et al. J Am Chem Soc 80 905 1958.] The procedure for purification via the picrate comprises the addition of quinoline to picric acid dissolved in the minimum volume of 95% EtOH to yield yellow crystals which are washed with EtOH and air dried before recrystallising from acetonitrile. The crystals are dissolved in dimethyl sulfoxide (previously dried over 4A molecular sieves) and passed through a basic alumina column, on which picric acid is adsorbed. The free base in the effluent is extracted with n-pentane and distilled under vacuum. Traces of solvent from small quantities are removed by vapour phase chromatography. The hydrochloride crystallises from EtOH with m 193o. [Mooman & Anton J Phys Chem 80 2243 1976, Beilstein 20 II 236, 20 III/IV 3410, 20/7 V 333.]

定義ChEBI: Isoquinoline is an ortho-fused heteroarene that is a benzopyridine in which the N atom not directly attached to the benzene ring. It is a mancude organic heterobicyclic parent, an azaarene, an ortho-fused heteroarene and a member of isoquinolines.