Chiral Ureas with Two Electronegative Substituents at 1-N: An Unusual Case of Coexisting Pyramidal and Almost Planar 1-N Atoms in the Same Crystal

摘要

XRD studies of structure of N-acetoxy-N-methoxyurea and N,N-bis (methoxycarbonyl)-N-methoxyimide have revealed that in N-methoxy-N-X-ureas (X = OAc, Cl, OMe, N+C5H5) the additional shortening of N-OMe bond took place, which arising from an n(O(Me))-sigma*(N-X) anomeric orbital interaction. XRD studies of N-chloro-N-ethoxyurea crystal have revealed the presence of two kinds of anomeric nitrogen configuration in the O-N-Cl group in the form of a pyramidal configuration and a planar configuration for same 1-N nitrogen atom. XRD studies of N-4-chlorobenzoyloxy-N-ethoxyurea have revealed that the degree of pyramidality of the 1-N nitrogen in N-aroyloxy-N-alkoxyureas is tuned by orientation of benzoyl group with respect to the N-O bond, which in turn depends of size of N-alkoxy group.