Herein, we disclose the Rh­(III)-catalyzed selective C8-alkylation of quinoline N-oxides with maleimides and acrylates. The main features of the reaction include complete C8-selectivity and broad substrate scope with good to excellent yields. The reaction also proceeded well with unprotected maleimide. The applicability of the developed methodology is demonstrated with gram-scale synthesis and post-modification of the alkylated product. Preliminary mechanistic study revealed that the reaction proceeds through a five-membered rhodacycle and involves proto-demetalation step.

A cobalt­(III)-catalyzed C-8 selective C–H amidation of quinoline N-oxide using dioxazolone as an amidating reagent under mild conditions is disclosed. The reaction proceeds efficiently with excellent functional group compatibility. The utility of the current method is demonstrated by gram scale synthesis of C-8 amide quinoline N-oxide and by converting this amidated product into functionalized quinolines. Furthermore, the developed catalytic method is also applicable for C-7 amidation of N-pyrimidylindolines and ortho-amidation of benzamides.

In the last two decades, rhodium-based catalysts have been used extensively for the sp 2 and sp 3 CÀ H bond activation/functionalization of various arenes, heteroarenes, and aliphatic compounds, respectively. For quinoline functionalization rhodium has been used significantly as compared to other transition metals such as cobalt, copper, ruthenium, palladium and iridium. In this Minireview the progress on rhodium-catalyzed selective functionalization of quinoline N-oxides and 8-methylquinolines via sp 2 and sp 3 CÀ H bond activation, respectively have been highlighted. The main focus is on reaction mechanism, substrate scope, and positional selectivity.