N-(2-Fluorophenyl)-2,6-dimethyl-1,3-dioxan-4-amine

In the title compound, C12H16FNO3, the dioxane ring adopts a chair conformation with the methyl groups and amine N atom in equatorial positions. The best plane through the dioxane ring makes a dihedral angle of 43.16 (8)° with the phenyl ring. In the crystal, pairs of C—H⋯O hydrogen bonds link the molecules into centrosymmetric R 2 2(8) dimers, which are linked into [100] chains by further C—H⋯O hydrogen bonds. The N—H group does not participate in hydrogen bonding.

In the title compound, C 12 H 16 FNO 3 , the dioxane ring adopts a chair conformation with the methyl groups and amine N atom in equatorial positions. The best plane through the dioxane ring makes a dihedral angle of 43.16 (8) with the phenyl ring. In the crystal, pairs of C-HÁ Á ÁO hydrogen bonds link the molecules into centrosymmetric R 2 2 (8) dimers, which are linked into [100] chains by further C-HÁ Á ÁO hydrogen bonds. The N-H group does not participate in hydrogen bonding.

Comment
Oxygen heterocycles play a vital role as basic building blocks in pharmaceutical preparations. This class of compounds has useful insecticidal as well as anti-foaming properties (Yuan et al., 2005). Dioxane rings are frequently encountered in structural motifs in many bioactive molecules such as cytotoxic agents (Aubele et al., 2005) and antimuscarinic agents (Marucci et al., 2005). As part of our studies in this area, we have undertaken a single-crystal structure determination of the title compound.
In the title compound, C 12 H 16 F 1 N 1 O 3 ( Fig.1), pairs of C-H···O hydrogen bonds link the molecules into centrosymmetric R 2 2 (8) dimers (Fig.2). The dimers are linked into an infinite chain propagating along the 'a′ axis by further C-H···O hydrogen bonds. The dioxane ring adopts a chair conformation and the best plane through the dioxane ring makes a dihedral angle of 43.16 (8)° with the phenyl ring.

Experimental
To 2-fluoroaniline (1 mmol), acetaldehyde (3 mmol) was added dropwise and stirred for about 4 h at 0 °C. The progress of the reaction was monitored through TLC. The reaction mixture was washed with petroleum ether. Resultant was dissolved in diethylether and allowed to evaporate. Solid product obtained was recrystallized for diethylether solution to yield colourless blocks.

Refinement
The hydrogen atoms were placed in calculated positions with C-H = 0.93 Å to 0.98 Å refined in the riding model with fixed isotropic displacement parameters:U iso (H) = 1.5U eq (C) for methyl group and U iso (H) = 1.2U eq (C) for other groups.

Figure 2
The crystal packing of the title compound viewed down b axis. H-atoms not involved in H-bonds have been excluded for clarity. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.