SN H Arylamination of 3-Nitropyridine: A Competitive Formation of 2-Arylamino-5-nitropyridines and 2-Arylamino-5-nitrosopyridines

Abstract

Arylamination of 3-nitropyridine via the nucleophilic substitution of hydrogen leads to a mixture of 2-arylamino-5-nitropyridines and novel 2-arylamino-5-nitrosopyridines, with the latter as the major product. The proposed mechanism includes the formation of σH-adducts and their further aromatization proceeding either through an oxidative pathway or intramolecular Red/Ox pathway of the SN H reaction. Moreover, we have shown that nitroso compounds can be selectively oxidized with m-chloroperbenzoic acid to give the corresponding nitro derivatives or their N-oxides, depending on the reaction temperature and the amount of oxidant.

Amination of Nitro-Substituted Heteroarenes by Nucleophilic Substitution of Hydrogen

“…Although the isolated yield was higher in the case of 3.0 equiv of 2a and 3.0 equiv of LiHMDS (entry 8), for economic reasons, we preferred to develop the reaction as in entry 6. While UPLC/MS traces of reaction mixtures did not appear messy, we did observe resinification that likely accounted for the remainder of the mass balance.…”

“…As previously mentioned, while we isolated nitro-(hetero)arenes 5, the products of related ONSH reactions are frequently isolated as the reduced nitrosoarenes in the absence of an exogenous oxidant. 5,10,15 We were unsure if we also accessed nitrosopyridine intermediates, but somehow our substrates happened to be oxidized by excess nitro(hetero)arene or by air. When the reaction between aniline 1b and nitropyridine 2a was monitored by in situ IR spectroscopy under a N 2 atmosphere, the instantaneous disappearance of the N�O stretch of 2a (1538 and 1360 cm −1 ) upon addition of LiHMDS coincided with the formation of a signal belonging to an intermediate (1390 cm −1 ) that decayed upon exposure to Scheme 3.…”