1,3,5-Trichloro-2,4,6-tris(dichloromethyl)benzene

Abstract

The asymmetric unit of the title compound, C 9 H 3 Cl 9 , contains one molecule. Two slightly different conformations with nearly C 3h symmetry are mutually disordered in a 1:1 ratio. This disorder enhances the overall structural symmetry to D 3h . Structure descriptionThe title compound (Fig. 1) is a central intermediate for star-shaped conjugated oligomers (Demenev et al., 2010;Detert et al., 2010). A bromo derivative has been reported by Holst et al. (2011). This compound combines our interest in perchloro hydrocarbons (Detert et al., 2009;Schollmeyer & Detert, 2017) and star-shaped discotic liquid crystals Glang et al., 2014).The asymmetric unit contains one molecule of the title compound and two very similar conformations with nearly C 3h symmetry occur in a 1:1 ratio (Fig. 2). This disorder enhances the symmetry of the overall structure to D 3h . Assuming the D 3h symmetry for one nondisordered molecule, the space group will rise from P4 3 to P4 3 2 1 2. However, then the refinement is not stable and the molecular symmetry is in contradiction to the chemistry. Distances between H atoms and ring-bound Cl atoms are 2.262 Å for H7Á Á ÁCl3 and also for H8Á Á ÁCl6, but the spacing between H9 and Cl9 is 2.43 Å . Similarly, two C-H bonds are nearly coplanar with the ring (H8-C8-C3-C4 = À3and H9-C9-C5-C6 = 3 ), whereas H7-C7-C1-C2 is twisted by À9 . Synthesis and crystallizationThe title compound was prepared according to Veciana et al. (1993) and Taerum et al. (2009) with the modification that a steel bomb (2.2 Â 25 cm) was used as reaction vessel. This allows scale-up to 3.0 g (16.5 mmol, 1.0 equivalent) 1,3,5-trichlorbenzene in 30 ml absolute chloroform with 2.7 g (19.8 mmol, 1.2 equivalents) AlCl 3 , and frequent pressure reduction was not necessary. The temperature was regulated with ISOHEAT

Tris(5‐aryl‐1,3,4‐oxadiazolyl)benzotrithiophenes – Discotic Liquid Crystals with Enormous Mesophase Ranges

“…Among the different approaches to trisubstituted BTTs, [1f,15] Perepichkas high‐yielding route (Scheme 1) leads straight‐forward to BTT‐tricarboxylic acid, [1f,5b] an ideal reactant for the formation of oxadiazoles. Starting with 1,3,5‐trichlorobenzene 1 , threefold Friedel‐Crafts alkylation with chloroform under pressure [1f,16] yields 1,3,5‐trichloro‐2,4,6‐tri(dichloromethyl)benzene 2 (Scheme 1). This is hydrolyzed in concentrated sulfuric acid in the presence of iron sulfate to form trialdehyde 3 .…”