Study of reactions between 1,2-diaza-1,3-butadienes and N,N′-diaryl- or N,N′-dialkylthioureas

1,2-Diaza-1,3-butadienes react with N,N′-diarylthioureas to give 2-(arylimino)-2,3-dihydrothiazole derivatives, whereas with N,N′-dialkylthioureas to afford 5,5-disubstituted 3-alkyl-2-(alkylimino)-thiazolidin-4-one derivatives. Under basic conditions, these last products surprisingly give rise to 2-thioxo-1,3,7-triazaspiro[4.4]non-8-en-4-one and 5-oxo-4-(4-substituted 5-oxo-2-thioxoimidazolidin-4-yl)-2,5-dihydro-1H-pyrazole derivatives. In acidic medium, 5,5-disubstituted 3-alkyl-2-(alkylimino)-thiazolidin-4-ones are converted into 2-(alkylimino)-1-thia-3,7-diazaspiro[4.4]non-8-en-4-ones. X-Ray crystal structures of two products were determined.