Cobalt(III)-Catalyzed C–H Amidation of Arenes using Acetoxycarbamates as Convenient Amino Sources under Mild Conditions
摘要:
The Co(III)-catalyzed direct C-H amidation of arenes has been developed using O-acylcarbamates as a convenient amino source. This reaction proceeded in high efficiency under external oxidant-free conditions with a broad range of arene substrates, including 6-arylpurines bearing sensitive functional groups, thus furnishing synthetically versatile arene N-carbamate products.
Intermolecular Amidation of Unactivated sp<sup>2</sup> and sp<sup>3</sup> C−H Bonds via Palladium-Catalyzed Cascade C−H Activation/Nitrene Insertion
作者:Hung-Yat Thu、Wing-Yiu Yu、Chi-Ming Che
DOI:10.1021/ja062856v
日期:2006.7.19
reactions. For the reaction of unactivated sp3 C-H bonds, beta-amidation of 1 degrees sp3 C-H bonds versus 2 degrees C-H bonds is preferred. The catalytic reaction is initiated by chelation-assisted cyclopalladation involving C-H bond activation. Preliminary mechanistic study suggested that the persulfate oxidation of primary amides should generate reactive nitrene species, which then reacted with the cyclopalladated
Radical dearomatization of arenes and heteroarenes
作者:David Crich、Mitesh Patel
DOI:10.1016/j.tet.2006.05.051
日期:2006.8
The stannane-mediated benzeneselenol-catalyzed addition of aryl iodides to a range of arenes and aromatic hetereocycles has been studied. With furan, thiophene, and several carbocyclic arenes, the addition takes place with quenching of the adduct radical by the catalytic selenol leading to moderate yields of aryl-dihydroarenes. With nitrogen heterocycles, on the other hand, it was not possible to suppress aromatization of the adduct radical and fully aromatized products were isolated. Aryl iodides bearing hydrogen bond donating groups in the ortho-position add to nitrogen heterocycles with high selectivity ortho- to the nitrogen, affording a simple one-step synthesis of potential chelating ligands. While 2-iodophenol is an excellent aryl radical source in these reactions, the homologous 1-iodo-2-naphthol fails owing to its reaction with diphenyl diselenide, which gives 1-phenylseleno-2-naphthol in high yield. (c) 2006 Elsevier Ltd. All rights reserved.
Direct Synthesis of Heterobiaryls by Radical Addition to Pyridine: Expeditious Synthesis of Chelating Ligands
作者:David Crich、Mitesh Patel
DOI:10.3987/com-04-s(p)34
日期:——
The addition of aryl radicals to pyridine may be affected in moderate yield on exposure of aryl iodides to tributyltin hydride, AIBN, and diphenyl diselenide in hot pyridine. Mixtures of ortho-, meta-, and para-aryl substituted pyridines are typically obtained. When the iodide is ortho-substituted with a hydrogen bond donor, such as o-iodophenol, significantly improved selectivity for ortho-substituted pyridines, with potential as bidentate chelating ligands, is obtained.