Discrimination among equals: A catalytic method for the selective oxidation of unprotected glycosides, both monosaccharides and disaccharides, has been developed. The resulting ketosaccharides are isolated in moderate to excellent yields. This approach provides a basis for protecting‐group‐free synthetic transformations of carbohydrates.
The reaction of readily available TEMPONa with aryl diazonium salts allows for clean generation of the corresponding aryl radicals along with TEMPO. Aryl radical addition to alkenes with subsequent TEMPO trapping provides the corresponding oxyarylation products in good to excellent yields. These experimentally easy to conduct transformations occur in the absence of any transition metal under mild conditions, and the process shows broad functional group compatibility.
A simple and practical method for the determination of rate constants for trifluoromethyl radical addition to various alkenes by applying competition kinetics is introduced. In the kinetic experiments the trifluoromethyl radicals are generated in situ from a commercially available hypervalent-iodine-CF3 reagent (Togni-reagent) by SET-reduction with TEMPONa in the presence of TEMPO and a π-acceptor. From the relative ratio of TEMPOCF3 and CF3-addition product formed, which is readily determined by (19)F-NMR spectroscopy, rate constants for trifluoromethyl radical addition to the π-acceptor can be calculated. The practical method is also applicable to measure rate constants for the addition of other perfluoroalkyl radicals to alkenes as documented for CF3CF2-radical addition reactions.
Reaction of various alkenes with commercially available N-fluorobenzenesulfonimide (NFSI) and TEMPONa provides the corresponding aminooxygenation products in moderate to good yields. Single electron transfer from readily generated TEMPONa to NFSI allows for clean generation of the corresponding bissulfonylamidyl radical along with TEMPO. N-radical addition to an alkene and subsequent TEMPO trapping provides the corresponding aminooxygenation product.
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