Method for Accessing Nitrogen-Containing, B-Heteroaryl-Substituted 2,1-Borazaronaphthalenes

Abstract

The azaborine motif provides a mimic of aromatic systems through replacement of a C=C bond with a B–N bond. In particular, 2,1-borazaronaphthalenes, accessible through robust methods of synthesis and subsequent functionalization, afford an ideal platform to use for a variety of applications. However, the scope of substructures for this archetype has been limited by the lack of nitrogen-containing heteroaryls that can be incorporated within them. In this study, modified reaction conditions were developed to provide access to a wider range of substructures.

Four-coordinate triarylborane synthesis via cascade B–Cl/C–B cross-metathesis and C–H bond borylation

“…On the basis of the above results and previous reports, 9 , 10 , 22 , 23 we proposed a mechanism for this cascade B–Cl/C–B cross-metathesis and C–H borylation reaction ( Scheme 6 ). An active aryldichloroborane A intermediate could be highly selectively obtained which was generated in situ by the addition of SiCl 4 to aryltrifluoroborates 9 when Ar 1 is an electron-deficient aryltrifluoroborate and Ar 2 is an electron-rich aryltrifluoroborate.…”

“…Intermediate A reacts with another aryltrifluoroborate (Ar 2 BF 3 K) via B–Cl/C–B cross-metathesis to obtain diphenylchloroborane B , and subsequent pyridine directed electrophilic aromatic borylation 10 of amine 1 eventually leads to four-coordinate triarylborane products 3 , 5–52 . In addition, intermediate A could also proceed via C–H bond borylation 9b , 23 with amine 1 , and subsequent fluorination 24 leads to by-product 4 . We can’t rule out the possibility of forming the four-coordinate triarylborane products via B–Cl/C–B cross-metathesis between intermediate D and another aryltrifluoroborate (Ar 2 BF 3 K).…”

Intramolecular (directed) electrophilic C–H borylation

“…However, Molander and co-workers subsequently suggested that pyridyl (and other Lewis basic N-heterocycles) coordination to main group Lewis acids was preventing N-directed borylation in their previous work. 61 Therefore they increased the amount of Lewis acid (SiCl 4 ) to two equivalents (with respect to the N-heterocycle) and included Et 3 N as a relatively hindered base.…”

Unveiling 79‐Year‐Old Ixene and Its BN‐Doped Derivative

“…[17,18] However,studies on the synthesis of BN-doped PA Hs and basic azaborine building blocks,such as 2,1-borazaronaphthalene derivatives, have been reported only sparsely. [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] Considering the potential electronics applications of these compounds,t his lack of research is surprising.However,itcan be attributed to the challenges associated with incorporating boron and nitrogen atoms at specific framework positions and the difficulties in subsequently forming CC bonds that further expand aromatic p-conjugation. [34,35] While studying the electronic properties of pyrene (Figure 1a), we noticed that among various pyrene derivatives, Clar et al (1970) reported only one isomer of pyrene fused with four benzene rings ( Figure 1b).…”