Mingchun Gao

Copper Nitrate Mediated Regioselective [2+2+1] Cyclization of Alkynes with Alkenes: A Cascade Approach to Δ2‐Isoxazolines

An efficient method for the regioselective synthesis of pharmacologically relevant polysubstituted Δ(2)-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.

Copper nitrate-mediated chemo- and regioselective annulation from two different alkynes: a direct route to isoxazoles

An efficient copper nitrate-mediated annulation reaction was developed for the direct synthesis of pharmacologically interesting polysubstituted isoxazoles in good to excellent yields from two different alkynes with high chemo- and regioselectivities by syringe pump infusion.

Manganese(II)-catalyzed modular synthesis of isoquinolines from vinyl isocyanides and hydrazines

An efficient manganese(II)-catalyzed oxidative radical cascade reaction was developed for the modular synthesis of multi-substituted isoquinolines from easily accessible vinyl isocyanides and hydrazines. Pyrrolo[1,2-a]quinoxalines and phenanthridines could also be afforded efficiently by this method and a wide range of alkyl, (hetero)aryl and alkoxycarbonyl substitutions could be easily introduced.

Transition Metal-Participated Synthesis and Utilization of N-containing Heterocycles: Exploring for Nitrogen Sources.

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.

Copper nitrate: a privileged reagent for organic synthesis

Copper has been explored as an ideal candidate for replacing noble metals in organic synthesis, especially for practical large scale preparation. Recent decades have witnessed the renaissance and improvement of copper-catalyzed and copper-mediated organic reactions. Copper nitrate is a common inorganic copper salt which has been proved to be a ubiquitous reactant in organic synthesis due to its commercial availability, stability, inexpensiveness and environmentally benign nature. Copper nitrate could be used as a nitration reagent, oxidant, catalyst or promoter, and Lewis acid as well. Remarkably, great attention has been devoted to the efficient transformation of copper nitrate into functionalized or complicated compounds through various reaction types including cyclization, C-H activation, difunctionalization, nitration, rearrangement and asymmetric synthesis with chiral ligands. Further modification of copper nitrate, such as solid-supported copper nitrate or copper nitrate complexes, extends its applications in organic synthesis. The present review highlights recent advances of copper nitrate in organic synthesis, along with the mechanisms.