(5RS,10SR,15RS)-Trimethyltruxene1

The title molecule, C30H24, was prepared as a possible precursor to buckminsterfullerene cages. The two enantiomers adopt the anti configuration, with one S/R and two R/S methyl groups, one anti to the other two. The truxene framework is slightly non-planar: with respect to the central six-ring mean plane, the three methyl C atoms are 1.377 (3), −1.475 (3) and 1.515 (3) Å distant, whereas the respective proximate peripheral six-ring mean planes make dihedral angles of 6.27 (6), 3.45 (7) and −7.37 (7)°.

The title molecule, C 30 H 24 , was prepared as a possible precursor to buckminsterfullerene cages. The two enantiomers adopt the anti configuration, with one S/R and two R/S methyl groups, one anti to the other two. The truxene framework is slightly non-planar: with respect to the central six-ring mean plane, the three methyl C atoms are 1.377 (3), À1.475 (3) and 1.515 (3) Å distant, whereas the respective proximate peripheral six-ring mean planes make dihedral angles of 6.27 (6), 3.45 (7) and À7.37 (7) .

Related literature
For related structures, see : De Frutos et al. (1999, 2002. For the synthesis of truxenes, see: Amick & Scott (2007); Dehmlow & Kelle (1997); Kipping (1894a,b); Hausmann (1889); Wislicenus (1887). For buckminsterfullerene, see: Kroto et al. (1985). Buckybowls are intermediates in the synthesis of buckminsterfullerene. Truxene compounds, which serve as backbone of bucky bowl derivatives, have been fabricated for use as star-shaped organic semiconductors in solution, see: Sun et al. (2005). Buckybowls have been recognized as valuable intermediates in the synthesis of buckminsterfullerene and also show many valuable and interesting properties, including surface selective chemistry. As a part of ongoing investigations for synthesis of bucky bowls, the title molecule, trimethyltruxene, C 30 H 24 , was prepared as a possible precursor to buckminsterfullerene cages. Furthermore, these truxene compounds, which serve as backbone of bucky bowl derivatives also have shown properties of organic field-effect transistors (OFETs) based on oligothiophene-functionalized truxene derivatives, which have been fabricated for use as novel star-shaped organic semiconductors in solution (Sun et al., 2005).

Experimental
Two isomers of the title compound, syn and anti are possible. De Frutos et al. (2002) prepared mixtures of the two isomers, which could be converted to the pure, more stable syn compound by reaction with base, potassium t-butoxide. We report here the structure of the less stable anti isomer, which is not a viable precursor for buckybowls.

Experimental
Synthesis of truxene was carried by the one-pot, acid catalyzed, head-to-tail cyclotrimerization synthesis method detailed in (Amick & Scott, 2007) The trimethylation of truxene was carried out by treating truxene with n-butyl lithium, followed by treatment with methyl iodide. A suitable single-crystal was obtained by recrystallization from diethyl ether, dichloromethane and methanol.

Refinement
All H atoms were placed in calculated positions, guided by difference maps, with C-H bond distances 0.95 (aromatic C), 1.00 (alkyl C) Å, and U iso =1.2U eq , thereafter refined as riding. A torsional parameter was refined for each methyl group, with C-H bond distances 0.98 Å and U iso = 1.5U eq . The largest peak in the final difference map was at the center of the C18-C26 bond, and the top 33 peaks lay near bond centers.