A sequential one-pot classical aldol, transition-metal and hydride-free reductive aldol reaction has been reported for C(sp3)-H functionalization of 2-oxindoles using multifaceted reagent rongalite. Here, rongalite functions as a hydride-free reducing...

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.

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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.