Carbon nanodots stand as the missing link between the molecular and the nanoscale world, owing to the unique molecular-like behavior emerging from their synthetic precursors. A converging set of analytical and spectroscopic data yields a precise inventory of the surface reactive groups of amine-rich carbon dots (NCDs-1). As a result, NCDs-1 provide a multi-functional nano-platform that is able to covalently activate carbonyl groups, form iminium-ions and enamine intermediates, and efficiently promote diverse aminocatalytic transformations in water. Remarkably, the catalytic activity of carbon dots can also govern the stereoselectivity in the bond-forming event. Indeed, the use of chiral carbon dots (NCDs-7) as catalysts affords the final aldol products with significant enantiomeric excess. The successful implementation of carbon nanostructures into chemical roles so far restricted to molecular systems opens new avenues for advanced applications where the nanoscale and the molecular realms will merge and complement each other.
C<scp>U</scp><sub>2</sub>O-Catalyzed C(<scp>SP</scp><sup>3</sup>)-H/C(<scp>SP</scp><sup>3</sup>)-H Cross-Coupling Using TEMPO: Synthesis of 3-(2-Oxoalkyl)-3-hydroxyoxindoles
作者:Baoshuang Wang、Jiayi Zhu、Yang Wei、Guotian Luo、Hongen Qu、Liang-Xian Liu
DOI:10.1080/00397911.2015.1111383
日期:2015.12.17
A simple, convenient, and efficient oxidative cross-coupling reaction of oxindoles with ketones toward a variety of 3-(2-oxoalkyl)-3-hydroxyoxindoles in moderate to excellent yields has been developed. This transformation proceeds via a tandem oxidative cross-coupling by using 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO) in air as an environmentally benign oxidant. This methodology provides an alternative approach for the direct generation of all-carbon quaternary centers at the C3 position of oxindoles.