6326-06-3Relevant articles and documents
Noninnocent Ligand in Rhodium(III)-Complex-Catalyzed C-H Bond Amination with Tosyl Azide
Fujita, Daiki,Sugimoto, Hideki,Morimoto, Yuma,Itoh, Shinobu
, p. 9738 - 9747 (2018)
Six-coordinate rhodium(III) complexes coordinated by a planar trianionic ligand (L3-) are synthesized. One of the axial positions is occupied by chloride (Cl-), bromide (Br-), or iodide (I-), and another axial position is coordinated by a solvent molecule such as acetonitrile (AN), water (H2O), tetrahydrofuran (THF), or pyridine (PY) to complete an octahedral rhodium(III) center; [RhIII(L3-)(X)(Y)]? (1X/Y X = Cl-, Br-, or I-, Y = AN, H2O, THF, or PY). Coordination of the AN, H2O, and THF ligands to the metal center is rather weak, so that these solvent molecules are easily replaced by PY to give [RhIII(L3-)(Cl)(PY)]?. In the electrochemical measurements, all complexes have two reversible redox couples based on the ligand-centered oxidation L3- to L·2- and to L-, as reflected by the very similar redox potentials regardless of the different axial ligands. The rhodium(III) complexes catalyze C-H bond amination of xanthene with tosyl azide (TsN3). Because the yields of the aminated product are nearly the same among the complexes, replacement of the axial solvent ligands with TsN3 readily occurs to give a nitrene-radical-bound rhodium(III) complex, [RhIII(L·2-)(N·Ts)(X)]?, as an active oxidant, which is generated by one-electron transfer from the trianionic L3- to the nitrene nitrogen atom. Generation of such a diradical intermediate was substantiated by the direct reaction of 1Cl/AN with TsN3 in the absence of the substrate (xanthene). In this case, a rhodium(III) iminosemiquinone complex, 2, was generated by the intramolecular reaction between the nitrene-radical moiety and the radical moiety of the ligand L·2-.
Benzylic oxidation and functionalizations of xanthenes by ligand trasfer reactions of hypervalent iodine reagents
Dohi, Toshifumi,Ito, Motoki,Kita, Yasuyuki,Komiyama, Keina,Ueda, Shohei,Yamaoka, Nobutaka
, p. 85 - 103 (2020/01/28)
The benzylic oxidation, amidation, and unprecedented heteroarylation proceed at room temperature using iodosobenzene, (sulfonylimido)iodobenzenes, and diaryliodonium(III) salts are described for the direct Csp3-H functionalizations of xanthene molecules. This study has demonstrated that hypervalent iodine reagents serve as unified synthetic tools for versatile xanthene Csp3-H transformations based on the radical and SET oxidation processes.
Organocatalytic nitrenoid transfer: Metal-free selective intermolecular C(sp3)-H amination catalyzed by an iminium salt
Combee, Logan A.,Raya, Balaram,Wang, Daoyong,Hilinski, Michael K.
, p. 935 - 939 (2018/02/07)
This report details the first organocatalytic method for nitrenoid transfer and its application to intermolecular, site-selective C(sp3)-H amination. The method utilizes a trifluoromethyl iminium salt as the catalyst, iminoiodinanes as the nitrogen source, and substrate as the limiting reagent. Activated, benzylic, and aliphatic substrates can all be selectively functionalized in yields up to 87%. A mechanistic proposal for the observed reactivity supported by experimental evidence invokes the intermediacy of a diaziridinium salt or related organic nitrenoid, species that have not been previously explored for the purpose of C-H amination. Finally, examples of late-stage functionalization of complex molecules highlight the selectivity and potential utility of this catalytic method in synthesis.
