Nitroaromatics and nitroheteroaromatics serve as key building blocks and intermediates in synthesis, and form the core scaffold of a vast number of materials, dyes, explosives, agrochemicals and pharmaceuticals. However, their synthesis relies on harsh methodologies involving excess mineral acids, which present a number of critical drawbacks in terms of functional group compatibility and environmental impact. Modern, alternative strategies still suffer from significant limitations in terms of practicality, and a general protocol amenable to the direct C-H functionalization of a broad range of aromatics has remained elusive. Herein we introduce a bench-stable, inexpensive, easy to synthesize and recyclable nitrating reagent based on saccharin. This reagent acts as a controllable source of the nitronium ion, allowing mild and practical nitration of both arenes and heteroarenes displaying an exceptional functional group tolerance.

Instrumentation and Analysis NMRNMR spectra were recorded at room temperature in deuterated solvents on Bruker AVANCE 300 (300 MHz) FT-NMR spectrometer. Chemical shifts (δ) are reported in units of parts per million relative to tetramethylsilane. All 1 H spectra were referenced to proton signals of residual undeuterated solvents. Mass spectrometryAn Agilent technologies 1100 series LC/MSD system equipped with a diode array detector and single quadMSdetector (VL) with an electrospray source (ESI-MS) was used for MS analysis. ESI accurate masses were measured on a LTQ Orbitap LTQ XL (Thermo-Fisher Scientific, Bremen) with loop injection. Contact AngleWater contact angles were measured by the sessile drop method on a DSA 100 goniometer (Krüss GmbH Wissenschaftliche Laborgeräte, Germany).

Demonstrated herein is the construction of trifluoromethylated quaternary carbon centers by an asymmetric radical transformation. Enantioenriched trifluoromethylated oxindoles were accessed using a hypervalent iodine‐based trifluoromethyl transfer reagent in combination with a magnesium Lewis acid catalyst and PyBOX‐type ligands to achieve up to 99 % ee and excellent chemical yields. Mechanistic studies were performed by experimental and computational methods and suggest a single‐electron transfer induced SN2‐type mechanism. This example is thereby the first report on the construction of enantioenriched trifluoromethylated carbon centers using hypervalent iodine‐based reagents proceeding through such a reaction pathway.

Herein, the synthesis and characterization of a hypervalent‐iodine‐based reagent that enables a direct and selective nitrooxylation of enolizable C−H bonds to access a broad array of organic nitrate esters is reported. This compound is bench stable, easy‐to‐handle, and delivers the nitrooxy (‐ONO2) group under mild reaction conditions. Activation of the reagent by Brønsted and Lewis acids was demonstrated in the synthesis of nitrooxylated β‐keto esters, 1,3‐diketones, and malonates, while its activity under photoredox catalysis was shown in the synthesis of nitrooxylated oxindoles. Detailed mechanistic studies including pulse radiolysis, Stern–Volmer quenching studies, and UV/Vis spectroelectrochemistry reveal a unique single‐electron‐transfer (SET)‐induced concerted mechanistic pathway not reliant upon generation of the nitrate radical.

Demonstrated herein is the construction of trifluoromethylated quaternary carbon centers by an asymmetric radical transformation. Enantioenriched trifluoromethylated oxindoles were accessed using ah ypervalent iodine-based trifluoromethyl transfer reagent in combination with amagnesium Lewis acid catalyst and PyBOX-type ligands to achieve up to 99 %eeand excellent chemical yields.Mechanistic studies were performed by experimental and computational methods and suggest as ingle-electron transfer induced S N 2-type mechanism. This example is thereby the first report on the construction of enantioenriched trifluoromethylated carbon centers using hypervalent iodine-based reagents proceeding through such ar eaction pathway. Scheme 1. Generally accepted mechanismso fCF 3 transfer from hypervalent iodine-based reagents 1 and 2 to nucleophilic substrates. a) Reductivee limination pathway.b)Radical pathway.c )Our work on the enantioselective radical trifluoromethylation of oxindoles by an SET-induced S N 2-type pathway.