Metal Nitrate Mediated Regioselective Nitration of BN-Substituted Arenes

Abstract

A regioselective nitration of BN-substituted arene compounds has been successfully developed. The first examples of BN-nitroarenes have been synthesized and structurally characterized by X-ray diffraction analysis. Photophysical studies of these novel compounds reveal an effective π conjugation between the nitro group and 1,2-azaborine moiety in the solution phase. A plausible mechanism for this nitration reaction is proposed.

Recent Developments in Azaborinine Chemistry

“…The nitration reactions failed when other aromatic ring substituents at the boron position were used. Although limited in scope, this system allowed the isolation of the first nitrated azaborinines, which would otherwise be inaccessible using standard aqueous nitration protocols …”

“…Although limited in scope, this system allowed the isolation of the first nitrated azaborinines, which would otherwise be inaccessible using standard aqueous nitration protocols. [44] Scheme 14. First report on the nitration of 1,2-azaborinines using metal nitrate hydrates.…”

Late-stage functionalization of BN-heterocycles

“…Fang developed an alternative method for bromination with CuBr 2 as the bromine source and acetyl chloride as an activating agent (Scheme 1c). 8 In another publication by the Fang group, the C3 position of 5 underwent electrophilic attack with NIS activated by AlCl 3 in high yield (Scheme 1d). 9 While the C3 position of the 1,2-azaborine attacks halogen electrophiles, the C5 position tends to engage in Friedel-Crafts reactivity.…”

“…In another report, Fang and co-workers developed a procedure for the regioselective nitration of 5 and 6 (Scheme 3b). 8 In the presence ofa metal-nitrate hydrate and acetyl chloride a nitro group is installed at the C5 position in good yield, likely via a radical mechanism. In the presence of radical scavengers compound 5 produced the C5-acetylated compound 9a.…”

The application of nitrogen oxides in industrial preparations of nitro compounds

“…Nitration reactions to form C‐N bonds have been widely used for the preparation of nitro compounds in numerous areas of applied research . Owing to the widespread presence of nitro compounds in pharmaceuticals, natural products, organic intermediates, catalysts, and high energy density materials, the application of this process has been exceptionally broad. However, based on the principles of green chemistry, most industrial nitration processes are less environmentally‐friendly because they use nitric acid, nitrates, and nitrous esters as nitrating agents .…”