2,3-Bis(trimethylsilyl)- and 2,3,8,9-tetrakis(trimethylsilyl)[4]phenylene

[ N ]Phenylenes: a Novel Class of Cyclohexatrienoid Hydrocarbon

“…Thus, a variety of substituted biphenylenes could be made by the cocyclization of 1,2-diethynylbenzene 2 with alkynes, in the case of bis(trimethylsilyl)acetylene (BTMSA) yielding 3 in a remarkable 96% yield (Scheme 4.2) [50]. Exploiting the silyl substituents as masked ethynyl groups and using tin instead of silicon, as appropriate [45], gave access to 4 and 6 and, hence, the linear homologs 5 [51] and 7 [52] by iterative sequences involving up to three separate co-oligomerization steps (for 7). These linear [N]phenylenes were targeted first for synthesis, because they are distinct from their angular isomers, as this topology (in which cyclobutadienoid circuits cannot be completely avoided) imparts relative electronic activation [53].…”

“…In this variant, a tetraethynylated arene precursor undergoes biscycloadditions to generate four rings in a single operation, leading to 9 [51,54], 11 [52], and 13 [55]. The power of the transition-metal-based approach is evident, when one recognizes that eight of the nine rings in 13 are made by [CpCo(CO) 2 ].…”

“…The smallest molecule with mixed linear/ angular connectivity is bent [4]phenylene 48 (Scheme 4.12), the last [4]phenylene isomer to be made [52,58,63,72]. This isomer is intriguing, in particular because of the unusual nature of the two juxtaposed internal six-membered rings and their surroundings.…”

Ring Currents in Benzo‐ and Benzocyclobutadieno‐Annelated Biphenylene Derivatives

“…Numerous [n]phenylenes have been synthesized so far [1][2][3][4][5] and their aromaticity/antiaromaticity has been scrutinized. [6][7][8] In addition, these compounds are of considerable interest from a photophysical and spectroscopic point of view.…”

Deuteration effects on the vibronic structure of the fluorescence spectra and the internal conversion rates of triangular [4]phenylene

“…6,8,13,15 After the synthesis of [N]phenylenes of various topologies, [16][17][18][19][20][21][22][23][24][25][26][27][28] the experimental confirmation of the theoretical data has become possible. The cyclohexatriene nature of the central ring of (1) in the ground state has been demonstrated experimentally by the chemical reactivity of this compound 29,30 and the X-ray diffraction data.…”