![]() ![]() These higher azaarene products were also achieved from other starting materials, such as 2-methyl-6-(phenylethynyl)pyridine, 2,6-dimethylpyridine ( 1a) and ( E)- N-benzylidene-4-methylbenzenesulfonamide, 2-bromo-6-methylpyridine and ( E)-styrylboronic acid, as well as 2-methylpyridine and phenylmethanamine. Due to the abundant importance of these products, several different approaches were reported ( Scheme 1 and Scheme 2). Different catalysts such as ionic liquids, CuFe 2O 4, and Ca(OTf) 2 were also utilized. Despite the low yield of the product of around 4%, this work described crystallographic data and the influence of reaction conditions such as the temperature and the reaction time on the stability of 1-phenyl-2-(2-pyridyl)ethanol. Castro and co-workers have also reported the synthesis of 1-phenyl-2-(2-pyridyl)ethanol and 1-phenyl-2-(2-pyridyl)ethene under catalyst- and solvent-free conditions. Nevertheless, the solvent was water, which required long extraction processes compared to solvent-free conditions. performed similar reactions without catalyst under microwave irradiation in the presence of water as a solvent, but when considering an industrial scale, there are numerous factors that serves as obstacles for the usage of microwave reactors, such as escalated heat loss, variations in the absorption, an inadequate penetrating ability of the radiation into the reaction medium, and further reflection of the microwaves. reported the functionalization of benzylic C–H bonds of 2-methylazaarenes by nucleophilic addition to aromatic aldehydes catalyzed by acetic acid using harmful chlorinated solvent, and this reaction suffers from longer reaction times. Recently, C(sp 3)–H functionalizations of methylazaarenes with isatins and malononitrile under catalyst-free conditions have been reported. ![]() The synthesis of pyridine and related azaarene derivatives involve the C(sp 3)–H activation of 2-methylpyridines using different transition-metal compounds, Lewis acids, and Brønsted acids. Huang and co-workers first realized the addition of alkylazaarenes directly to unsaturated bonds via C(sp 3)–H functionalization. ![]() In the past years, C−H bond functionalization catalyzed by transition metals received a strong emphasis, and other different catalytic systems have also been encouraged. Such methodologies are omnipresent and facilitate sustainable organic transformations for the synthesis of complex natural products and pharmaceuticals. The formation of new C–C bonds through direct C–H bond functionalization in organic chemistry is attractive. Thus, in this regard the further development of this approach is still in need to be developed. The synthesis of higher cores of nitrogen-containing heterocyclic compounds through C(sp 3)–H functionalization of simple compounds like methyl azaarenes allows direct transformation without any critical reaction conditions. Mainly, 2-substituted quinolines and their analogues exhibits magnificent bioactivity. These compounds act as anti-HIV and anti-asthma drugs. Due to their conformational diversity, these compounds constitute a motif in various natural alkaloid products, such as chimanine and those derived from lobelia, sedum, etc. The functionalization of alkylpyridines and quinolines is significant and plays a remarkable role in the efficient drug design. Among various nitrogen-containing heterocyclic compounds, pyridine and quinolines are readily found in bioactive compounds. The recent advancements in nitrogen-containing carbon compounds have marked them as an unusual moiety due to their attractive applications in biology and as materials. Azaarenes are a distinct class of heterocyclic compounds possessing wide compatibility in the field of synthetic organic chemistry. ![]()
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