From saddle-shaped diketones, Kwan Yin Cheung, Xiaomin Xu, and Qian Miao, The Chinese University of Hong Kong, China, have synthesized two new aromatic saddle-shaped polycyclic arenes containing two heptagons, C₇₀H₂₆ and C₇₀H₃₀. The carbonyl groups of the diketons are the key in the reactions to extend the polycyclic π-framework.

Local aromaticity and nonplanarity of individual rings in the saddle-shaped π-backbone were anlyzed on the basis of crystal structures. For 1b and 2b they were found to follow Clar’s rule in general. 1b and 3b behaved as p-type semiconductors in solution-processed thin film transistors; the amorphous films of 2b appeared insulating.

• Aromatic Saddles Containing Two Heptagons,
  Kwan Yin Cheung, Xiaomin Xu, Qian Miao,
  J. Am. Chem. Soc. 2015.
  DOI: 10.1021/jacs.5b00403