Cycloaddition von Heterocumulenen an CN‐Bindungssysteme. 1. Mitteilung. Perhydro‐s‐triazindione und Perhydro‐s‐triazinyl‐harnstoffe aus N,N,N′‐trisubstituieten Formamidinen und Isocyanaten

The addition of methyl isocyanate to N,N‐dimethyl‐N′‐arylformamidines 4d–4r leads to the perhydro‐s‐triazine‐diones 5d–5o and to the s‐triazinylureas 10a–10k. The mechanism of formation is discussed. The addition of the arylisocyanates 18a–18p to the N,N,N′‐trialkylformamidines 9 and 27a–27i furnishes the expected 1,4‐cycloaddition products 26 and 27 in good yields. The N,N‐di‐isopropyl‐N′‐alkylformamidines 27j–271, however, do not undergo 1,4‐dipolar cycloadditions and react with the arylisocyanate 18b to yield the alkyl isocyanates 31a–31c and N,N‐diisopropyl‐N′‐(p‐chlorphenyl)‐formamidine 32 exclusively.