This account aims to describe our recent efforts on the synthesis and utilization of N-containing heterocycles, where transition metals participate in the synthesis. A variety of nitrogen sources, including amines, amides, hydrazones, pyrimidines, isocyanides, and copper nitrate, have been disclosed for the synthesis of diverse bioactive and pharmacologically interesting N-containing heterocycles under the participation of transition metals. The well-known nitrogen sources, such as amines and amides, were used for the construction of indoles, isatins, and quinolones. Dihydrophthalazines, isoquinolines, indazoles, and pyrazoles were obtained from hydrazones, while various pyrimidine-containing heterocycles were afforded through regioselective C−H functionalizations using pyrimidine as the directing group. Recent research has focused on the chemistry of isocyanides to achieve several kinds of heterocyclic compounds with high efficiency under the catalysis of transition metals (Pd, Rh, Mn, Cu), through oxidative cyanation reactions, sequential isocyanide insertions into C−H, N−H, or O−H bonds, and tandem radical annulation. More recently, an efficient route to isoxazolines has been reported using copper nitrate as a novel nitrogen source.

Degradation of the highly reactive hypervalent trifluoromethylation iodine reagent PhI(OAc)(CF₃), which can only be generated in situ with mixing PhI(OAc)₂ and TMSCF₃ in the presence of CsF, was studied by ESI-MS and GC-MS combined with ¹⁹F-NMR. The important transient intermediate PhICF₃⁺ was determined by ESI-MS, and the major volatile products containing CF₃ were identified with the authentic compounds by using GC-MS, such as trifluoromethylbenzene, 2-iodobenzotrifluoride, 3-iodobenzotrifluoride, 4-iodobenzotrifluoride. Meanwhile, more evidences obtained with ¹⁹F-NMR were given for such degradation reaction. A possible rapid CF₃ radical transfer reaction pathway was proposed to clarify such degradation progress based on the experimental results. Therefore, this study may be helpful in elucidating the intrinsic reactivity of PhI(OAc)(CF₃) and the possible competing side reactions caused by such self-degradation pathway.

An efficient method for the regioselective synthesis of pharmacologically relevant polysubstituted Δ²-isoxazolines is based on the copper-mediated direct transformation of simple terminal alkynes and alkenes. The overall process involves the formation of four chemical bonds with inexpensive and readily available copper nitrate trihydrate as a novel precursor of nitrile oxides. The reaction can be easily handled and proceeds under mild conditions.

An efficient method for the regioselective synthesis of pharmacologically relevant polysubstituted Δ²-isoxazolines is based on the copper-mediated direct transformation of simple terminal alkynes and alkenes. The overall process involves the formation of four chemical bonds with inexpensive and readily available copper nitrate trihydrate as a novel precursor of nitrile oxides. The reaction can be easily handled and proceeds under mild conditions.

An efficient and mild synthesis of imidazo[1,2-a]pyrimidine derivatives has been developed from readily available pyrimidyl arylamines or enamines through a hypervalent iodine-promoted intramolecular C–H bond cycloamination reaction. This protocol allows for the facile construction of biologically active bicyclic imidazo[1,2-a]pyrimidine skeletons as well as other imidazo[1,2-a]-type fused heterocycles.

A wide variety of ortho-halogenated arylpyrimidines were prepared with high monoselectivity and functional-group tolerance by using calcium halides as crucial halogenating agents and cupric trifluoroacetate as oxidant in the presence of air.

An efficient and regioselective palladium-catalyzed orthoC–H acetoxylation reaction was developed to afford ortho monoacetoxylated arylpyrimidines in good to excellent yields by using cupric trifluoroacetate as a cocatalyst. A wide variety of oxygenated arylpyrimidines were prepared with high regioselectivity and functional group tolerance.