3,3'-Dibromo-5,5'-di-tert-butyl-2,2'-dimethoxy-biphen-yl.

The title compound, C(22)H(28)Br(2)O(2), crystallizes in a staggered arrangement to minimize the inter-actions of its ortho substituents, with a dihedral angle of 84.2 (3)° between the two aromatic rings. Short C-H⋯O hydrogen-bonding inter-actions between meth-oxy groups result in a one-dimensional polymeric chain of mol-ecules lying parallel to the b axis. One tert-butyl group is disordered equally over two positions.

The title compound, C 22 H 28 Br 2 O 2 , crystallizes in a staggered arrangement to minimize the interactions of its ortho substituents, with a dihedral angle of 84.2 (3) between the two aromatic rings. Short C-HÁ Á ÁO hydrogen-bonding interactions between methoxy groups result in a one-dimensional polymeric chain of molecules lying parallel to the b axis. One tert-butyl group is disordered equally over two positions.

Comment
During attempts to dilithiate 2,6-dibromo-4 − t-butylanisole, the title compound, (I), was serindipitously produced. Compared to the literature methods (Katagiri et al., 2006) this is a much simpler method, wherein the product was acheived in a single step rather than three and with a superior overall yield. The structure adopts a staggered arrangement with a dihedral angle of 84.2 (3)° between the two aromatic rings. A similar angle is found in the literature (80. 1°, He & Ng, 2006). Two CH 3 ···O hydrogen bonds involving both methoxy groups (Table 1) connect the molecules to form a one dimensional polymeric chain parallel to the b axis ( Figure 2); similar type of interactions have already been reported (Steiner, 1996).
Experimental 2,6-Dibromo-4 − t-butylanisole (1 g) in THF (40 ml) at 193 K was treated with n-butyl lithium (1.6 M, 2.5 ml). The solution was stirred and allowed to warm up to room temp over 2 hr. The resulting solution was evaporated to dryness, treated with water and extracted with dichloromethane. The organic layer was seperated and purified by column chromotography (SiO 2 , dichloromethane). Yeild = 0.6 g (79%).

Refinement
The methoxy groups are both evenly disordered over two sites. One tert-butyl group is disordered over two sites whilst the other is not. This breaks the potential symmetry between the two halves of the molecule. Both tert-butyl groups exhibited elongation of the thermal elipsoids and have been restrained (ISOR) to be more isotropic. The large redidual electron density (1.11 e/A*3) is located 0.64Å from H70A and is probably related to a small amount of unmodelled tert-butyl group disorder.
All H-atoms were positioned geometrically and refined using a riding model with d(C-H) = 0.95 Å, U iso = 1.2U eq (C) for aromatic, and 0.98 Å, U iso = 1.5U eq (C) for CH 3 atoms. Fig. 1. A view of the asymmetric unit of (I), showing displacement ellipsoids at the 50% probability level. All hydrogen atoms have been omited for clarity. The bonds for one of the disordered parts are displayed as hollow bonds.    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 > 2sigma(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.