Huang Hui, Stewart Timothy, Gutmann Matthias, Ohhara Takashi, Niimura Nobuo, Li Yu-Xue, Wen Jian-Feng, Bau Robert, Wong Henry N C
Shanghai-Hong Kong Joint Laboratory in Chemical Synthesis, Shanghai Institute of Organic Chemistry, The Chinese Academy of Sciences, 354 Feng Lin Road, Shanghai 200032, China.
J Org Chem. 2009 Jan 2;74(1):359-69. doi: 10.1021/jo802061p.
Two chiral tetraphenylenes, 2,15-dideuteriotetraphenylene (7) and 2,7-dimethyltetraphenylene (15) were synthesized and resolved to address the tetraphenylene inversion barrier problem. Neutron diffraction investigation of enantiopure 7 showed that the molecule retained its chirality integrity during its synthesis from enantiopure precursors and therefore rules out the possibility of the tetraphenylene framework possessing a low-energy barrier to inversion. Thermal study on 15 and tetraphenylene 1 further revealed that their inversion barriers were not overcome up to 600 degrees C, at which temperature these compounds underwent skeletal contraction into triphenylene with activation energies of 62.8 and 58.2 kcal/mol, respectively. This result is supported by computational studies which yielded an inversion barrier of 135 kcal/mol for tetraphenylene as a consequence of the peri-hydrogen repulsions at its planar conformation.
合成并拆分了两种手性并四苯，即2,15-二氘代并四苯（7）和2,7-二甲基并四苯（15），以解决并四苯翻转势垒问题。对纯对映体7的中子衍射研究表明，该分子在由纯对映体前体合成过程中保持了其手性完整性，因此排除了并四苯骨架具有低能翻转势垒的可能性。对15和并四苯1的热学研究进一步表明，在高达600℃时它们的翻转势垒仍未被克服，在此温度下这些化合物发生骨架收缩形成三亚苯，活化能分别为62.8和58.2 kcal/mol。这一结果得到了计算研究的支持，计算研究表明，由于并四苯平面构象中的邻位氢排斥作用，其翻转势垒为135 kcal/mol。
