1,4,6,9-Tetra-tert-butyl-2,7-dioxatricyclo[6.3.0.03,6]deca-3,8-diene

The title compound, C24H40O2, lies on an inversion center with a half-molecule in the asymmetric unit. The central dioxane ring adopts a chair conformation. The four-membered ring is slightly puckered with a butterfly angle of 13.50 (14)°.

The title compound, C 24 H 40 O 2 , lies on an inversion center with a half-molecule in the asymmetric unit. The central dioxane ring adopts a chair conformation. The four-membered ring is slightly puckered with a butterfly angle of 13.50 (14) .

Crystal data
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: ZL2528).  (Rauk et al. 1995) led to the synthesis of the title compound. The stereochemistry of the title compound was not known at that time. In the title compound ( Fig. 1), the central dioxane ring adopts a chair conformation with puckering parameters: Q = 0.3934 (11) Å, θ = 0.74 (1)° and φ = 0.0°. The four membered ring (C1/C2/C3/C4 i ; i = -x + 1, -y + 1, -z + 1) is slightly puckered with the dihedral angle between mean planes C1/C2/C3 and C1/C3/C4 i being 13.50 (14)°. The molecular dimesions in the title compound agree very well with the corresponding molecular dimensions reported in closely related compounds (Masters et al., 1994;Bernassau et al., 1987). The crystal structure is devoid of any significant directional intermolecular interactions (Fig. 2).

Experimental
The synthesis of the title compound has been reported earlier (Rauk et al., 1995). Crystals suitable for crystallolgraphic studies were grown from pentane/CH 2 Cl 2 (1:1).

Refinement
Though the H-atoms were observable in the difference electron density maps they were included at geometrically idealized positions with C-H distances = 0.99 and 0.98 Å for methylene and methyl type H-atoms, respectively. The Hatoms were assigned U iso = 1.2 times U eq (C).

Computing details
Data collection: COLLECT (Hooft, 1998); cell refinement: DENZO (Otwinowski & Minor, 1997); data reduction: SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008  ORTEP drawing (Farrugia, 2012) of the title molecule with the displacement ellipsoids plotted at 50% probability level; H atoms are presented as small spheres of arbitrary radius. Symmetry code: i -x + 1, -y + 1, -z + 1.  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.