A novel, efficient and green protocol for the copper‐catalyzed azide–alkyne cycloaddition (CuAAC) reaction by using copper nanoparticles (CuNPs), generated in situ by a green reducing agent, rongalite, is reported. Terminal alkynes reacted with benzyl, aryl and alkyl azides in the presence of copper nanoparticles and β ‐cyclodextrin (β‐CD) in water. The reactions exclusively generated the corresponding regiospecific 1,4‐disubstituted 1,2,3‐triazoles in good to excellent yields. Notably, in situ generation of copper nanoparticles does not require any additional stabilizing agents or special reaction conditions. β‐cyclodextrin plays dual role as a stabilizing agent as well as phase transfer catalyst. This protocol is also applicable for gram scale reactions.
A molecular iodine catalyzed regioselective insertion of isocyanide into C2-H of quinoline N-oxides has been developed. The reaction proceeds through the nucleophilic addition of isocyanide on quinoline Noxides followed by rearrangement in presence of iodine. This metal-free reaction affords rapid access to quinoline 2-formamides with exceptional functional group tolerance, broad substrate scope and 100% atomeconomy. A library of 33 N-(2-quinolinyl)formamides are synthesized, which may find applications in pharmaceuticals and synthetic chemistry.
A logic-based replacement of the carboxylic acid component
of the
Ugi reaction by quinoline N-oxides has been developed.
In this approach, the carboxylic isostere, quinoline N-oxide, plays a vital role by shifting the equilibria toward the
product side with irreversible addition onto the C2-position of the N-oxide. Thus, aldehydes react with amines, isocyanides,
and quinoline N-oxides to furnish quinoline four-component
Ugi adducts. The unique reactivity of N-oxides with
Ugi components opens an efficient synthetic route for the preparation
of biologically active compounds.
A simple and convenient synthesis of nitriles from the corresponding aldoximes using methyl 2‐nitrosobenzoate under milder condition has been developed. The reaction proceeds under weak alkaline conditions and, allows for the conversion of a wide variety of aldoximes including aromatic aldoximes, and heterocyclic aldoximes in good to excellent yields in short time. Notably, α, β‐unsaturated aldoximes were also compatible with the reaction conditions without any cis/trans isomerization of the double bonds. An unprotected hydroxyl and amine group has no effect on the reaction outcome.
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