Rotational Isomerism Involving an Acetylenic Carbon II : Effect of 1-Halogen Substituents on Rotamer Population and Rotational Barrier around C(sp)-C(sp<sup>3</sup>) Bonds in Bis(9-triptycyl)ethynes
l)ethynes were synthesized to examine the effect of halogen substituents on the rotational isomerism about C(sp)-C(sp3) bonds. The kinetic and thermodynamic data of the isomerization between the ap and sc rotamers were determined by the total lineshape analysis and the intensity of the 1H NMR signals, respectively. The rotationalbarriers are enhanced with the steric size of halogen atoms from 11.6
Atropisomerism in Doubly<i>peri</i>-Substituted 9-(2-Methylbenzyl)triptycene Derivatives, 8-Chloro- and 8-Bromo-1,4-dimethyl-9-(2-methylbenzyl)triptycenes
作者:Gaku Yamamoto、Takashi Nemoto、Yuji Ohashi
DOI:10.1246/bcsj.65.1957
日期:1992.7
9-(2-methylbenzyl)triptycene has an energy barrier to gear rotation of 11.8 kcal mol−1 (1 cal = 4.184 J). Introduction of substituents at two of the peri-positions was expected to raise the barrier enough for atropisomerism to be realized in this system. Actually, two stable rotational isomers, ap and sc*(9S*), were separately isolated for 8-chloro- (7) and 8-bromo-1,4-dimethyl-9-(2-methylbenzyl)triptycene (8).
properties of dibenzozethrenes were explored. The results thus obtained were compared with those for zethrenes. Dibenzozethrenes were synthesized by the nickel‐catalyzed cyclodimerization of 9‐ethynyl‐1‐iodoanthracenes. The substituents in zethrene and dibenzozethrene twisted their backbones, and remarkably influenced their properties. Unlike closed‐shell disubstituted derivatives, the parent zethrene and dibenzozethrene
探索了二苯并并蒽的合成,结构和物理性质。将由此获得的结果与zethrenes的结果进行比较。二苯并并蒽是通过镍催化的9-乙炔基-1-碘代蒽的环二聚反应合成的。并戊烯和二苯并并蒽中的取代基扭曲了它们的主链,并显着影响了它们的性能。与闭壳二取代衍生物不同,母体蒽和二苯并蒽均是单峰开壳双自由基,其研究是通过可变温度1进行的。1 H NMR,ESR,SQUID和计算方法。由于观察到取代基显着影响双自由基性质,因此分析了相关机理。这些化合物各自的非线性光学性能取决于其π共轭和双自由基性质。Dibenzozethrenes具有较大的双光子吸收横截面大于zethrenes,因为大多数强烈由父dibenzothrene [证明σ最大= 4323 GM在530nm]。