Thermal cyclisation of an alleneamidine to a dihydropyridine derivative involving a 1,5‐hydrogen shift

The alleneamidins 1 has been shown to cyclise to a dihydropyridine derivative 2 by heating for a 2 hours at 220°. This reaction is assumed to proceed via a (1, 5 a)‐sigmatropic hydrogen shift followed by a 6 π‐electrocyclisation. An attempt has been made to extend this new heterocyclisation. Copyright © 1976 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim