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+C5H5) the additional shortening of N–OMe bond took place, which arising from an nO(Me)‐σ*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.