Neue Synthesen von Heterocyclen mit Vinyl‐ und Divinylcarbodiimiden: Pyrrole, Triazole, Pyrimidine, Pyrindine, Isochinoline und Thiazolyl‐isothiazole

New Syntheses of Heterocycles with Vinyl‐ and Divinylcarbodiimides: Pyrroles, Triazoles, Pyrimidines, Pyrindines, Isoquinolines and Thiazolyl‐isothiazoles The title compounds 3 and 4 react with diazomethane either by loss or by retention of the diazo nitrogen, to afford 3,4‐dihydro‐2‐imino‐2H‐pyrroles 6 and 10 or the vic‐triazole 5, respectively. The structure of 5 has been established by X‐ray diffraction analysis. – The [4 + 2] addition of benzylidene methylamine or alicyclic enamines 9 to 4 results in the formation of partially hydrogenated pyrimidine 7, pyrindine 11a or isoquinoline 11b. – Thermolysis of 4 proceeds with spontaneous dehydrogenation, giving high yields of 1‐(1‐in‐dolyl)isoquinolines 8. – The derivative 10a, when melted with sulfur, undergoes both dehydrogenation and sulfur insertion, whereby the hitherto unknown thiazolyl‐isothiazole 13 is formed. Its structure has been elucidated by an X‐ray diffraction analysis. – A synthesis of the imidazo[2,1‐a]isoquinoline derivative 16 is reported. magnified image