Tert-Butylnitrite Mediated Regioselective C(sp(2))-3 Nitration of Substituted 4-Quinolones and Its Late-stage Manipulations

A novel and eco-friendly technique for the synthesis of C-3 nitro derivatives of 4-quinolones via the regioselective C(sp(2))-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.