7,11,15,28-Tetrakis[(2-formylphenoxy)methyl]-1,21,23,25-tetramethylresorcin[4]arene cavitand ethyl acetate clathrate at 173 K

The title compound, C68H56O16, was synthesized as a novel synthetic intermediate towards deeper and more elaborate resorcin[4]arene cavitands. The structure is the first reported example of a resorcin[4]arene cavitand bearing aromatic aldehyde functional groups at the extra-annular rim of the molecule. The 2-formylphenoxy residues are found to assume two different orientations above the molecular cavity. One half of the resorcin[4]arene cavitand molecule appears in the asymmetric unit; the complete resorcin[4]arene cavitand structure was generated across a mirror plane. In addition, a highly disordered ethyl acetate solvent molecule is present within the molecular cavity.

The title compound, C 68 H 56 O 16 , was synthesized as a novel synthetic intermediate towards deeper and more elaborate resorcin[4]arene cavitands. The structure is the first reported example of a resorcin[4]arene cavitand bearing aromatic aldehyde functional groups at the extra-annular rim of the molecule. The 2-formylphenoxy residues are found to assume two different orientations above the molecular cavity. One half of the resorcin [4]arene cavitand molecule appears in the asymmetric unit; the complete resorcin[4]arene cavitand structure was generated across a mirror plane. In addition, a highly disordered ethyl acetate solvent molecule is present within the molecular cavity. Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT-NT (Bruker, 2005); data reduction: SAINT-NT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2009 Kay et al. (2007Kay et al. ( , 2008. For the implemetation of the SQUEEZE function in PLATON, see: Tam et al. (2005).

Related literature
The title compound exhibits two different orientations of the 2-formylphenoxy residues, which are present above the molecular cavity. Two adjacent residues appear upright, while the remaining two appear splayed, in an orientation almost perpendicular to the first two residues. This relative orientation is illustrated in Fig. 2 (above the molecular cavity) and However, the ethyl acetate was of a highly disordered nature. Therefore, in the final refinement model, the electron density related to the disordered ethyl acetate molecule was removed by using the SQUEEZE function of PLATON (Spek, 2009). This resulted in an improved refinement model, and eliminated the ill-effects of the disorder upon the refinement.
The contribution of the ethyl acetate molecule was not included in the molecular formula, but is detailed in the SQUEEZE results which are appended to the CIF text. This further accounts for the discrepancies seen in the calculated and reported parameters of molecular weight, density and absorption coefficient.

S2. Experimental
To a stirring solution of salicylaldehyde (1.01 g, 8.30 mmol) in dry THF (70 ml) under a nitrogen atmosphere, NaH (60% suspension in mineral oil, 0.33 g, 8.30 mmol) was added. To the resulting bright yellow solution, bromomethyl cavitand (I) (1.00 g, 1.04 mmol) was added as a solution in dry THF (10 ml), dropwise over 30 minutes. The solution was refluxed for 4 days; TLC showed mono-, di-, tri-and tetra-substituted products. Over this time, the solution became grey in colour. Once cooled to room temperature, the solution was concentrated in vacuo. The products were chromatographed on silica gel using a mobile phase of 3:2 hexane-ethyl acetate. Fractions of 12 ml were collected, combining all fractions supporting information containing the desired tetra-substituted product (R f =0.37) after separation. The purified product was concentrated using a rotary evaporator to yield an off-white solid; this was then stirred in methanol overnight. After filtration, the product was collected and stirred overnight in hexane to remove residual aldehyde, before being filtered and collected to yield the title compound as a white solid.  189.83,160.93, 154.04, 139.09, 135.88, 129.70, 125.56, 121.77, 121.43, 114.18, 100.00,62.07, 31.22, 16.14 Crystals suitable for X-ray crystallography were grown by slow evaporation of a solution of the title compound in 1:1 ethyl acetate:hexane, at ambient temperature.

S3. Refinement
The crystal structure was solved by direct methods using SHELXTL (Sheldrick, 2008). Non-hydrogen atoms were first refined isotropically followed by anisotropic refinement by full matrix least-squares calculations based on F2 using SHELXTL. Hydrogen atoms, first located in the difference map, were positioned geometrically and allowed to ride on their respective parent atoms, with C-H bond lengths of 1.00 (CH), 0.99 (CH 2 ), or 0.98 (CH 3 ). They were then refined with a riding model with U iso (H) = 1.5U eq (CH 3 ) and U iso (H) = 1.2U eq (X) for X = CH or CH 2 .
One of the 2-formylphenoxy residues is disordered. The residue was refined over two positions with the final occupancies being 0.789 (4) for atoms O5, O39 and C32-38, and 0.211 (4) for atoms O5A, O39A and C32A-38 A. The largest residual electron density peak of 0.64 e/Å 3 is 0.92 Å from H38A.  The molecular structure of the title compound, as viewed from above the molecular cavity. Displacement ellipsoids are drawn at the 30% probability level. The relative orientations of the 2-formylphenoxy residues are evident. The dashed line indicates the mirror plane, which passes through C2, C10, and C21-23.  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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (