Tert‐Butylnitrite Mediated Regioselective C(sp²)−3 Nitration of Substituted 4‐Quinolones and Its Late‐stage Manipulations

Abstract

A novel and eco‐friendly technique for the synthesis of C‐3 nitro derivatives of 4‐quinolones via the regioselective C(sp2)−H bond functionalization employing tert‐butyl nitrite as nitrating agent in presence of TEMPO [(2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl] as an oxidant is unfolded herein. The protocol is scalable as well as high yielding with wide substrate scope and broad functional group tolerance. In‐depth mechanistic investigations revealed that the reaction occurred through a free radical pathway. The nitro derivatives of 4‐quinlones were selectively reduced to corresponding aminated 4‐quinolones. Finally, the photophysical properties of synthesized amine derivatives were also investigated, and some of them showed good fluorescence properties.

Palladium-Catalyzed, Site-Selective C(sp2)8–H Halogenation and Nitration of 4-Quinolone Derivatives

“…Great strides have been fabricated in recent years toward the synthetic manifolds, albeit exclusive site-selective C–H functionalization of the 4-quinolone nucleus is still at very nascent stage. Particularly, quinolin-4(1 H )-one nucleus embraces six distinguishable C–H bond, among them the C–3 position is more nucleophilic, and has witnessed commendable progress over the years. , In contrast, the direct and selective functionalization at the less activated benzenoid core (C5–C8 position) in the presence of bare C2–H imposes a significantly challenging task in transition metal catalysis. In this regime, the noble metal complexes of Pd, Ru, Rh, and Ir have been extensively fostered for regioselective C–H functionalization and subsequent annulations en route to carbon–carbon and carbon-heterobond formation .…”