for 2a, b, 38 h at 100 "C in 30 mL of NEt, with 250 mg of (Ph,P),PdCI,, 250 mg of CuI. and 500 mg of Ph,P; for la, c, 180 and 43 h, respectively, in 20 mL of NEt, with 100 mg of (Ph,P),PdCI,, 100 mg of CuI, and 250 mg of Ph,P). Workup was performed by treating the reaction mixture with petroleum ether (PE, b.p. 30-70°C) or ether, followed by filtration. The filtrate was washed with 2 M hydrochloric acid as well as with saturated aqueous sodium chloride solution, dried over magnesium sulfate, filtered, and evaporated to dryness under vacuum. Products la-c were purified by flash chromatography on 100 mL of silica gel 60 (E. Merck, 230-400 mesh; eluent PE/ethyl acetate (EE) lOO/l) and repeated crystallization from acetone and heptane. The triphenylenehexaynes 2 a, b were each purified by column chromatography on 400 mL of silica gel 60 (E. Merck, 70-230 mesh; eluent PE/EE lOO/l) and subsequent recrystallization (2a, 2 x from acetone, 1 x from heptane, 3 x from acetone containing 30% 1,2-dichlorobenzene, and 6 x from acetone; 2b, 1 x from acetone containing 30% 1,2-dichlorobenzene and 20 x from acetone).The phase transition data were obtained by polarizing microscopy (PM, Leitz Laborlux 12 Pol with a Mettler FP 82 hot stage, usual rate of heating 1 K min-') and by DSC (Mettler TA 3000/DSC 30 S and Graphware TA 72, usual heating rate 5 K min-I). The hexaynes 1 and 2 described here are multimorphic in the solid phase with reproducible solid/solid transitions and/or form4epending on the thermal history of the sample-metastable modifications. The value given as the melting point refers in each case to the highest-melting crystal modification; if necessary. !his modification was obtained by suitable thermal pretreatment of the samples (e.g., annealing or a second heating). K = crystalline, N, = nematicdiscotic. I = isotropic phase. Hexakis[(4-pentylphenyl)ethynyl]benzene 1 a (C,,H,,, M , = 1099.7): Yield 46%. yellow crystals from heptane, m.p. (K + N,) = 169.5'C (PM), 170.4"C (DSC. AH = 44.1 kJ mol-I), clearing point (N, + I ) % 187 'C (PM, owing to the strong tendency of this compound to decompose, only an approximate transition temperature could be measured. after determining the rough transition temperature, a fresh sample was placed in the hot stage at a temperature just below this value and the sample was heated at 10 K min-I), 184.9 "C (DSC, sh, 4.946). 350 (5.199). 'H NMR partial spectrum (Bruker WH 400, CDCI,): 6 = 7.6 and 7.2 (2 d, 'J(H,H) z 8 Hz each; phenyl H ortho and meta to C-C); 2.6 (t, 'J(H.H) = 7.5 Hz; a-CH,), 1.7 (tt, ,J(H,H) = 7.5 Hzeach; B-CH,). I3C NMR .2'C (PM). 156.8"C (DSC, AH = 36.7 kJ mol-I), clearing point (N, + I) = 236.6 C (PM, owing to the strong tendency of this compound to decompose, only an approximate transition temperature could be measured; after determining the rough transition temperature, a fresh sample was placed in the hot stage at a temperature just below this value and the sample was heated a! 10 K min-'), 237.1 "C (DSC, AH = 0.1 kJ mol-I 10,ll -Hexakis(l-decyny1)triphenyle...
