Thioacyl- and Imidoylcarbodiimides

thioacyl- and imidoylcarbodiimides, having a C=X (X = O, S, or NR) adjacent to the cumulative bond are usually not stable at room temperature. However, sterically hindered N-functional carbodiimides with aliphatic t-butyl groups or aromatic 2,6-dimethylphenyl groups are often more stable, and they are generated in situ, for subsequent reactions. For example, N-alkyl substituted imidoylcarbodiimides, RN=C(Ph)N=C=NR are only stable as crystalline compounds for a short period of time. Even in chloroform solution they undergo subsequent reactions as indicated by the disappearance of the carbodiimide infrared band (see Table 5.1).  

In contrast, phenylimidoylcarbodiimides PhN=C(R)N=C=NR, isomerize in solution to fom aminoquinazolines. Other imidoylcarbodiimides also undergo intramolecular rearrangements. For example, RR CHN=C(CCl3)N=C=NAr 1 undergoes a rearrangement to form dihydro-1,3,5-triazines 2  

A review article on acyl-, thioacyl- and imidoylcarbodiimides appeared in 1992.  

Chemistry and Technology of Carbodiimides Henri Ulrich 2007 John Wiley Sons, Ltd. ISBN 978-0-470-06510-5 

---

The remaining chapters are carbodiimides with unsaturated substituents, halogenated carbodiimides, acyl-, thioacyl- and imidoylcarbodiimides, silicon substituted carbodiimides, nitrogen substituted carbodiimides, phosphorous substituted carbodiimides, sulfur substituted carbodiimides, metal substituted carbodiimides, cyclic carbodiimides, polymeric carbodiimides and application of carbodiimides. 

---