Neuere heterocyclische Zwischenprodukte für die Azokupplung durch Cyclisierung von Nitrilen

Abstract

Two types of syntheses of heteroaromatic amines by cyclization of nitriles are described. It is dealt with the cyclization of nitriles by elemental sulphur yielding thiophenes and thiazoles and with some reactions of the resulting 2-amino-thiophene-3-carboxylic acid derivatives available from cyanoacetic acid derivatives, sulphur, and carbonyl compounds. Further a survey is given about syntheses with the last step being the THORPE-cyclization. Thus the syntheses of the following heterocyclic systems are possible: 3-aminothiophenes and -pyrroles, aminothienothio-phenes, -isothiazoles, -pyrazoles, -pyridines, -pyrimidines, -pyrazines, -thianaphthenes, -thiachromones, 3-aminothianaphthenes and -indoles, 4-amino-thiazoles, -isothiazoles, -isoxazoles, -imidazoles and -pyrazoles, 3-amino-benzofuranes and -furopyridines, 2-amino-indolizines.