title: 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.
abstract: 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(+)C(5)H(5)) 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.
authors.affiliation: STC Institute for Single Crystals, National Academy of Sciences of Ukraine, Kharkov, Ukraine.
authors.forename: Oleg V
authors.initials: OV
authors.lastname: Shishkin
authors.forename: Vasiliy G
authors.initials: VG
authors.lastname: Shtamburg
authors.forename: Roman I
authors.initials: RI
authors.lastname: Zubatyuk
authors.forename: Dmitriy A
authors.initials: DA
authors.lastname: Olefir
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Tsygankov
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Prosyanik
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Mazepa
authors.forename: Remir G
authors.initials: RG
authors.lastname: Kostyanovsky