Synthesis of Tetracoordinate Boron‐Fused Benzoaceanthrylene Analogs via Tandem Electrophilic C−H Borylation

Abstract

Benzoaceanthrylene analogs with tetracoordinate boron at the ring junction were synthesized through tandem electrophilic CÀHb orylation of 2,6-dinaphthylpyridine followed by nucleophilic substitution. Notably,t he [5,6]-annulation occurred selectively over [6,6]-annulation with the assistance of nitrogen coordination of the pyridine ring. The X-ray crystallographic analysis revealed the polycyclic skeleton with ad istorted tetracoordinate boron atom and au nique packing structurew ith intermolecular p-p interaction. The photophysical and electrochemical properties of these benzoaceanthrylene analogs were evaluated by UV-vis spectroscopy and differential pulse voltammetry.The electron affinity of the fluorine-substituted derivative is estimated to be 3.49 eV from the ionization potentiala nd opticalb and gap. Thus, this derivative is expected to be ap romising n-type semiconducting material.

Intramolecular (directed) electrophilic C–H borylation

“…In contrast, due to the presence of a tetrahedral boron centre (preferring bond angles around boron {1201) compound P was found to be 4.7 kcal mol À1 higher in energy than 98 and was not observed during borylation. 91 The mechanism of N-BX 3 mediated intramolecular C-H borylation was explored computationally by Uchiyama and Wang using 2-phenylbenzimidazole. 92 Starting from BBr 3 and BCl 3 borenium cations, 100, were found to be key intermediates on the C-H borylation pathway (boreniums may be more readily accessible in this case due to a BQN containing resonance form stabilising the borocation to a greater extent than possible with [pyridylBX 2 ] + , 93 Scheme 46, inset top right).…”

Multi-resonant thermally activated delayed fluorescence emitters based on tetracoordinate boron-containing PAHs: colour tuning based on the nature of chelates

“…S2.5 ‡). Furthermore, the B ) N bond lengths in BN1 and TCz-BN1 (1.679 Å and 1.698 Å, respectively) are much longer than those of other reported C^N^C (1.572 to 1.617 Å) 26,36 and O^N^O (1.579 Å) 27 tridentate boron compounds due to the signicant steric congestion introduced by the two TCz units. As a result of the tetrahedral geometry of the boron centre in both BN2 and BN3, the B-N TCz bond lengths (1.50-1.54 Å) are within the typical range of B-N single bonds, and longer than the analogous bonds in N^B^N-doped PAHs (1.40-1.41 Å).…”

Regioselective Transition‐Metal‐Free C(sp2)−H Borylation: A Subject of Practical and Ongoing Interest in Synthetic Organic Chemistry

“…[92][93][94][95] Very recently, an azobenzenedirected ortho-CÀ H borylation to give 71 was reported; 71 was further cyclized in a Grignard reaction to produce the 1,2,3-benzodiazoborole compound (not shown here). [96] By taking advantage of a pyridine directing group, a concerted double electrophilic CÀ H borylation on neighbouring arene moieties to give 72 [97] and 73 [98] was reported.…”