Crystal structure and C-H⋯F hydrogen bonding in the fluorinated bis-benzoxazine: 3,3'-(ethane-1,2-di-yl)bis-(6-fluoro-3,4-di-hydro-2H-1,3-benzoxazine).

Augusto Rivera,Michael Bolte,Jaime Ríos-Motta,Jicli José Rojas

doi:10.1107/s2056989016015243

Abstract

The title fluorinated bis-benzoxazine, C18H18F2N2O2, crystallizes with one half-mol-ecule in the asymmetric unit, which is completed by inversion symmetry. The fused oxazine ring adopts an approximately half-chair conformation. The two benzoxazine rings are oriented anti to one another around the central C-C bond. The dominant inter-molecular inter-action in the crystal structure is a C-H⋯F hydrogen bond between the F atoms and the axial H atoms of the OCH2N methyl-ene group in the oxazine rings of neighbouring mol-ecules. C-H⋯π contacts further stabilize the crystal packing.

Highlights

H F hydrogen bond between the F atoms and the axial H atoms of the OCH2N methylene group in the oxazine rings of neighbouring molecules
Even though benzoxazines have been known for more than 60 years, a cursory look at the literature cited in relation to the polybenzoxazines in recent years reveals increasing interest in polybenzoxazine chemistry (Demir et al, 2013)
Mannich condensation of a phenol and a primary amine with formaldehyde is perhaps the best synthetic route widely employed for the preparation of a variety of benzoxazine monomers

Summary

Chemical context

Even though benzoxazines have been known for more than 60 years, a cursory look at the literature cited in relation to the polybenzoxazines in recent years reveals increasing interest in polybenzoxazine chemistry (Demir et al, 2013). We have investigated the crystal structures of several bis-benzoxazines namely 3,30 -(ethane1,2-diyl)bis(6-substituted-3,4-dihydro-2H-1,3-benzoxazine). Supramolecular features derivatives (Rivera et al, 2010, 2011, 2012a,b) These were prepared to determine whether replacement of the substituents at the para position of the phenol affects the molecular conformation and possible supramolecular aggregation. In this context, the title compound is a model for studying nonconventional molecular interactions where the halogen atom may act as a hydrogen-bond acceptor. We report the crystal structure of 3,30 -(ethane-1,2-diyl)bis(6-fluoro-3,4-dihydro-2H1,3-benzoxazine) (I), which is a very good candidate as a monomer for the investigation of the polymerization of fluorine-containing bis-benzoxazine monomers. A database search yielded four comparable structures, 3,30 -(ethane-1,2-diyl)bis(6-methyl-3,4-dihydro-2H-1,3-benzoxazine) (AXAKAM; Rivera et al, 2011), 3,30 -ethylenebis(3,4dihydro-6-chloro-2H-1,3-benzoxazine) (NUQKAM; Rivera et al, 2010), 3,30 -(ethane-1,2-diyl)-bis(6-methoxy-3,4-dihydro2H-1,3-benzoxazine) monohydrate (QEDDOU; Rivera et al., 2012b), and 3,30 -(ethane-1,2-diyl)bis(3,4-dihydro-2H-1,3benzoxazine) (SAGPUN; Rivera et al, 2012a)

Synthesis and crystallization

Database survey