Di-tert-butyl 2,2′-(biphenyl-2,2′-diyldioxy)diacetate

The title compound, C24H30O6, does not exhibit π–π interactions due to the steric effect of the bulky tert-butyl groups present in the molecule. The presence of these groups at the 2 and 2′ positions hinders the free motion of the benzene rings relative to each other, causing them to adopt an antiperiplanar arrangement. The benzene rings are twisted by just under 50.96 (17)° with respect to each other. The carbonyl groups within the molecule are directed in different directions, one towards the biphenyl group and the other away from it. The molecules are linked together by C=O⋯H—C hydrogen bonds.

The title compound, C 24 H 30 O 6 , does not exhibitinteractions due to the steric effect of the bulky tert-butyl groups present in the molecule. The presence of these groups at the 2 and 2 0 positions hinders the free motion of the benzene rings relative to each other, causing them to adopt an antiperiplanar arrangement. The benzene rings are twisted by just under 50.96 (17) with respect to each other. The carbonyl groups within the molecule are directed in different directions, one towards the biphenyl group and the other away from it. The molecules are linked together by C OÁ Á ÁH-C hydrogen bonds.

Comment
Biphenyl moieties have been found to act as pharmacophores in many biological studies such as antimycobacterial testing (Kamoda et al., 2006). Several derivatives of biphenyl are reported to be potential inhibitors of HRV-2 (Makarov et al., 2005). However, they also show carcinogenic activity (Weisburger et al., 1967). Furthermore, they occupy a unique place in various classes of organic compounds not only due to their prevalence as the core framework of numerous natural products, but also for their use as chiral reagents, as chiral phases for chromatography, and as chiral nucleophilic catalysts (Spivey et al., 1999). Biphenyl derivatives are also used as precursors for the synthesis of oligo(p-phenylene)s (Sisson et al., 2006).
Oligo(p-phenylene)s have been extensively studied in the domain of artificial ion channels (Litvinchuk et al., 2004). Our interest in the synthesis of biphenyl derivatives stems from the fact that we wish to attach macrocycles like porphyrins and calix[4]arenes to oligo(p-phenylene)s to obtain functionalized pores (Baudry et al., 2006). In order to achieve these goals the synthesis of a number of biphenyl derivatives has been accomplished (Ali et al., 2008;Ibad et al., 2008). In this paper we report the synthesis and crystal structure of the title compound (I).
The OCH 2 C(═O)OC(CH 3 ) 3 residues are twisted away fom the biphenyl, as seen in the value of the C14-O4-C15-C16 torsion angle of 67.83 (14). The crystal packing diagram (Fig. 2) shows that there are fairly strong C-H···O interactions that are 0.2 Å less than the sum of the van der Waals radii, which results in the molecules forming chains in the c-direction.
Experimental K 2 CO 3 (414 mg, 3 mmol) and 2,2'-dihydroxybiphenyl (186 mg, 1 mmol) in 15 ml of acetone were stirred for 10 minutes, followed by addition of tertiary butyl bromoacetate (371 mg, 3 mmol). The reaction mixture was stirred at room temperature for three hours. Solvent was evaporated under reduced pressure and the residue was dissolved in a mixture of water (50 ml) and dichloromethane (50 ml). The aqueous layer was extracted three times with dichloromethane.The combined organic phases were evaporated under reduced pressure and the solid residue was dissolved in hot hexane. Slow evaporation of hot hexane gave colorless crystals (736 mg) in 80% yield.

Refinement
All H atoms were geometrically fixed and allowed to ride on the corresponding non-H atom with C-H = 0.96 Å and U iso (H) = 1.5U eq (C) of the attached C atom for methyl H atoms and 1.2U eq (C) for other H atoms.  Di-tert-butyl 2,2'-(biphenyl-2,2'-diyldioxy)diacetate