Metal-free synthesis of cyclic di-oxoguanidines via one-pot sequential transformation of amines, carbodiimides and acyl dichlorides.

The one-pot sequential reaction of various amines, carbodiimides, and acyl dichlorides has been achieved for the first time under metal-free conditions to provide symmetric cyclic di-oxoguanidines via an unexpected 2,2-dichloro-imidazolidindione intermediate. Acyl dichlorides have a dual function: to serve as the third component and to activate carbodiimides. In sharp contrast, the AlMe(3)-catalyzed sequential reaction from the same substrates gives the isomer.