A copper-mediated multi-component reaction was developed through isocyanide insertion into N-H bonds of less active secondary arylamines. This approach leads to an efficient synthesis of unsymmetrical tetrasubstituted ureas in one pot.
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.
An efficient copper nitrate-mediated chemo- and regioselective annulation reaction of two different alkynes was developed to achieve polysubstituted isoxazoles.
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.
A novel method was developed for the construction of biologically active poly-substituted cinnolines from easily accessible hydrazones in good to excellent yields. A simple copper catalyst could efficiently promote CÀN bond formation through selective CÀH functionalization and dehydrogenative amination. Furthermore, the inert CÀHeteroatom (O/F/N) bonds are susceptible to cleavage in high selectivity in the newly developed aerobic annulation, in preference to the alternative CÀH bond, which is left intact.
An unprecedented copper-mediated anion transformation is reported, along with selective CC double bond cleavage and dipolar cycloaddition reaction from simple alkenes and inexpensive copper nitrate. Various transformations demonstrate the generality of this method. Further mechanistic investigation indicates a novel ionic pathway for alkene cleavage and highlights the coeffect of iodide and boric acid as additives on the inhibition of well-documented competitive nitration byproducts.
An efficient copper nitrate mediated chloronitration reaction was developed for the direct synthesis of α-chloro-β-nitroolefins with high regio- and stereoselectivity from simple alkynes and low toxic stannous chloride. This protocol provides a direct access to polysubstituted alkenes with operational simplicity, good functional group tolerance, and a wide substrate scope. Various applications of given products allowed the straightforward assembly of molecular complexity and indicated them as promising and valuable building blocks in organic synthesis.
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