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.