Reaction of trimethylsilyl cyanide with isocyanates and carbodiimides

Trimethylsilyl cyanide reacts with isocyanates to give 1 2 cycloadducts, 5-(trimethylsilylimino)imidazolidine-2,4-diones, in high yield. The reaction of trimethylsilyl cyanide with carbodiimides proceeded in the presence of a catalytic amount of aluminum trichloride to afford 1 1 adducts, N-trimethylsilyl-1-cyanoformamides. At rather high temperatures, the reaction also proceeded without catalyst. The adducts were further allowed to react with isocyanates and carbodiimides to yield 4-imino-5-(trimethylsilylimino)imidazolidin-2-ones and 2,4-diimino-5-(trimethylsilylimino)imidazolidines, respectively. On the other hand, the reaction of trimethylsilyl cyanide with methyl isothiocyanate gave a novel cycloadduct, 4-cyano-5-bis(trimethylsilyl)aminoimidazolidine-2-thione.