N-Chloro-N-alkoxyureas:: synthesis, structure and properties

The XRD studies of N-chloro-N-alkoxyureas 1, 2 have revealed the high pyramidality of the amide nitrogen in the O-N-Cl group caused by n(O)-sigma(N-Cl)* anomeric effect, the other sequence of this effect is anionic lability of the chlorine atom; nucleophilic substitution at the nitrogen depends on the N'-substitutent nature: chlorine atoms in ureas 1 and 5 are replaced by outer nucleophile whereas, under the same conditions, ureas 2-4 undergo cyclization into 1-alkoxybenzimidazolin-2-ones 10-12.