Search

Electron‐transfer photocatalysis provides access to the elusive and unprecedented N‐pyridyl radical cation from selected N‐substituted pyridinium reagents. The resulting C(sp2)−H functionalization of (hetero)arenes furnishes versatile intermediates for the development of valuable aminated aryl scaffolds. Mechanistic studies that include the first spectroscopic evidence of a spin‐trapped N‐pyridyl radical adduct implicate SET‐triggered, pseudo‐mesolytic cleavage of the N−X pyridinium reagents mediated by visible light. [ABSTRACT FROM AUTHOR]

Abstract: Fluorine chemistry has taken a pivotal role in chemical reaction discovery, drug development, and chemical biology. NMR spectroscopy, arguably the most important technique for the characterization of fluorinated compounds, is rife with highly inconsistent referencing of fluorine NMR chemical shifts, producing deviations larger than 1 ppm. Herein, we provide unprecedented evidence that both spectrometer design and the current unified scale system underpinning the calibration of heteronuclear NMR spectra have unintentionally led to widespread variation in the standardization of 19F NMR spectral data. We demonstrate that internal referencing provides the most robust, practical, and reproducible method whereby chemical shifts can be consistently measured and confirmed between institutions to less than 30 ppb deviation. Finally, we provide a comprehensive table of appropriately calibrated chemical shifts of reference compounds that will serve to calibrate 19F spectra correctly. [ABSTRACT FROM AUTHOR]

The hydrophosphorane HP(OC 6 H 4 NMe) 2 was used to prepare the diastereotopic complexes [MCl 2 {P(OC 6 H 4 NMe)OC 6 H 4 NHMe}] (M = Pd, Pt) by reaction with [MCl 2 (PhCN) 2 ], and [RhCl(PPh 3 ){P(OC 6 H 4 NMe)OC 6 H 4 NHMe}] by reaction with [RhCl(PPh 3 ) 3 ]. To form these complexes, the phosphorane undergoes ring-opening, whereby it is coordinated as the tautomeric neutral phosphoramidite-amino chelating ligand. The crystal structure of [RhCl(PPh 3 ){P(OC 6 H 4 NMe)OC 6 H 4 NHMe}] was determined and the geometry about the Rh(I) atom is square-planar with cis-disposed phosphorus-donor ligands. The Rh–P distance is shortened (2.1056(6) Å) due to Rh( d ) → P π-backbonding. In addition, [RhCl(PPh 3 ){P(OC 6 H 4 NMe)OC 6 H 4 NHMe}] was shown to be an effective regio- and stereoselective catalyst for the hydrosilylation of 1-octene and 1-hexyne. [ABSTRACT FROM AUTHOR]