Twisted Polycyclic Arenes from Tetranaphthyldiphenylbenzenes by Controlling the Scholl Reaction with Substituents

• Published in: Chemistry : a European journal 2016-12, Vol.22 (51), p.18620-18627
• Main Authors: Yang, Yong, Yuan, Luyan, Shan, Bowen, Liu, Zhifeng, Miao, Qian
• Format: Article
• Language: English
• Subjects: arenes; Aromatic compounds; Backbone; Chemistry; Crystal structure; Isomerization; Isomers; Mathematical analysis; organic semiconductors; oxidative cyclodehydrogenation; polycycles; regioselectivity; Synthesis (chemistry); Thin films
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201604649

Herein, we report two new types of twisted polycyclic arenes (2 a, b and 3 a, b) with constitutionally isomeric π‐backbones, which are synthesized by controlling the Scholl reaction of 1,2,4,5‐tetra(naphth‐2‐yl)‐3,6‐diphenylbenzene (1) with properly positioned electron‐donating substituents. With a polycyclic backbone containing two [5]helicene and four [4]helicene moieties, 2 a and b are new members of multiple helicenes with interesting stereochemistries. The as‐synthesized 2 a and b are the twisted isomers, and thermal isomerization of twisted‐2 b results in anti‐2 b, a more stable stereoisomer. Both twisted‐ and anti‐2 b have been fully characterized, and the thermal isomerization of twisted‐2 b has been studied with 1H NMR spectroscopy and DFT calculations. Compounds 3 a and b are new members of twistacenes, the benzannulated pentacene backbone of which exhibits an end‐to‐end twist as found from the crystal structure. Twisted‐ and anti‐2 b are also found to function as p‐type semiconductors in solution‐processed thin film transistors, whereas the thin films of 3 b appear insulating presumably due to the lack of π–π interactions. Let's twist again: Two new types of twisted polycyclic arenes with constitutionally isomeric π‐backbones are synthesized by controlling the Scholl reaction of 1,2,4,5‐tetra(naphth‐2‐yl)‐3,6‐diphenylbenzene with properly positioned electron‐donating substituents (see scheme).