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

In the title compound, C12H16BrNO2, the dioxane ring adopts a chair conformation and its mean plane makes a dihedral angle of 60.63 (12)° with the 4-bromophenyl ring. In the crystal, molecules are linked by pairs of N—H⋯O hydrogen bonds, forming inversion dimers with an R 2 2(8) ring motif. These dimers are consolidated by pairs of C—H⋯O hydrogen bonds with an R 2 2(16) ring motif. Adjacent dimers are connected via C—H⋯O hydrogen bonds, forming infinite chains propagating along the c-axis direction.

In the title compound, C 12 H 16 BNO 2 r, the dioxane ring adopts a chair conformation and its mean plane makes a dihedral angle of 60.63 (12) with the 4-bromophenyl ring. In the crystal, molecules are linked by pairs of N-HÁ Á ÁO hydrogen bonds, forming inversion dimers with an R 2 2 (8) ring motif. These dimers are consolidated by pairs of C-HÁ Á ÁO hydrogen bonds with an R 2 2 (16) ring motif. Adjacent dimers are connected via C-HÁ Á ÁO hydrogen bonds, forming infinite chains propagating along the c-axis direction.

Comment
Dioxane rings are frequently encountered as structural motifs in many bioactive molecules such as cytotoxic agents (Aubele et al., 2005) and antimuscarinic agents (Marucci et al., 2005). 1,3-dioxane derivatives have applications in fine medicinal chemistry in the pharmaceutical (Wang et al., 1996a) and cosmetic industries (Wang et al., 1996b;Yuan et al., 2005). In view of the excellent biological and pharmacological applications of this class of compounds, we report herein on the synthesis and crystal structure of the title compound.
In the crystal, molecules are linked by a pair of N-H···O hydrogen bonds forming inversion dimers with an R 2 2 (8) ring motif (Bernstein et al., 1995). These dimers are consolidated by a pair of C-H···O hydrogen bonds with an R 2 2 (16) ring motif. Adjacent dimers are connected via C-H···O hydrogen bonds forming infinite chains propagating along the c axis (see Table 1 and Fig. 2 for details).

Experimental
To 4-bromoaniline (1 mmol), acetaldehyde (3 mmol) was added drop wise and stirred for about 4 h at 273 K. The progress of the reaction was monitored through TLC. On completion of the reaction the mixture was washed with petroleum ether. The resultant product was dissolved in diethylether and allowed to evaporate. Block-like colourless crystals of the title compound were obtained by recrystallization with diethylether.

Refinement
The NH H atom was refined with a distance restraint of N-H = 0.86 (2) Å with U iso (H) = 1.2U eq (N). The C bound H atoms were placed in calculated positions and refined as riding atoms: C-H = 0.93 -0.98 Å with U iso (H) = 1.5U eq (C-methyl) and = 1.2U eq (C) for other H atoms.

Figure 2
The crystal packing of the title compound viewed along the a axis. The hydrogen bonds are shown as dashed lines (see Table 1 fro details; H atoms not involved in hydrogen bonding have been omitted 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.