The electrophilic behavior of the reactive entity in the phtosubstitution of benzenes with 2-iodopyridine was found to be ascribable to the intermediary 2-pyridyl cation, rather than to the electrophilic 2-pyridyl radical.
A novel synthesis of 4-aryl- and 4-heteroarylpyridines via diethyl(4-pyridyl)borane.
作者:MINORU ISHIKURA、TSUKASA OHTA、MASANAO TERASHIMA
DOI:10.1248/cpb.33.4755
日期:——
A convenient method for the preparation of 4-aryl- and 4-heteroarylpyridines by the palladium-catalyzed cross-coupling reaction of diethyl (4-pyridyl) borane with aryl and heteroaryl halides is described.
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.