Boron‐Mediated Regioselective Aromatic C−H Functionalization via an Aryl BF₂Complex

Abstract

An efficient regioselective functionalization of 2aryl-heteroarenes and aryl aldehydes via an azaaryl BF 2 complex has been developed. Mechanistically the reaction comprises fluoride to bromide ligand exchange on an aryl boron species and consecutive CÀ B bond cleavage to deliver a broad range of functionalized products. The reaction is high yielding, has a broad substrate scope where several different heteroarenes can be functionalized with chloro, bromo, iodo, hydroxyl, amine and BF 2 in a highly regioselective fashion. The method can be applied for late-stage functionalization or for rapid skeleton remodeling with for instance crosscouplings.

Metal-Free ortho C–H Borylation of Thiobenzamides

“…On the basis of the results described above and previous reports, , a mechanism is proposed for this metal-free C–H borylation reaction (Scheme ). Initially, the coordination of 1a to BBr 3 formed Lewis acid–base adduct A , which further produced borenium cation B via the transfer of a bromide anion to another BBr 3 .…”

“…Impressively, in 2019, the groups of Shi and Houk and Ingleson simultaneously reported the metal-free acyl-directed electrophilic C–H borylation of anilines and indoles with BBr 3 accessing the ortho -borylated anilines and C4/C7-borylated indoles. Since then, a variety of acyl-, nitrogen-, and phosphine-directed metal-free ortho -selective aromatic C–H borylations using BBr 3 have been successively developed using a similar strategy . Inspired by these reports, we envisioned that the ortho C–H borylation of thiobenzamides might be achieved via a S-directed electrophilic borylation approach, although it has seldom been explored .…”

Phenalenyl-Based Photocatalyst for Bioinspired Oxidative Dehydrogenation of N-Heterocycles and Benzyl Alcohols

“…2-Bromobenzaldehyde (4h). 24 The crude mixture was purified by column chromatography on a silica gel (hexane/EtOAc as an eluent), and product 4h (22.6 mg, 61% yield) was obtained as a colorless liquid. 1 H NMR (500 MHz, CDCl 3 ) δ 10.34 (s, 1H), 7.92−7.86 (m, 1H), 7.65−7.61 (m, 1H), 7.45−7.39 (m, 2H); 13 C{ 1 H} NMR (126 MHz, CDCl 3 ) δ 191.9, 135.4, 134.0, 133.6, 130.0, 128.0, 127.2.…”

Boron-Mediated Regiospecific Ortho Halogenation of N-Aryl Am-ides and Ureas: Harnessing Boron Reactivity for Efficient C-X Bond Formation

“…[7] More recently, we showed that the chemistry is not limited to only hydroxyl and Bpin, but it can also be used for installing halogens to phenyl pyridines and aryl aldehydes (Figure 1C). [8] Figure 2. This work: Boron-directed regiospecific halodeboronation of N-aryl amides and ureas.…”