Modulating Reactivity and Diverting Selectivity in Palladium-Catalyzed Heteroaromatic Direct Arylation Through the Use of a Chloride Activating/Blocking Group
作者:Benoît Liégault、Ivan Petrov、Serge I. Gorelsky、Keith Fagnou
DOI:10.1021/jo902515z
日期:2010.2.19
Through the introduction of an aryl chloride substituent, the selectivity of palladium-catalyzeddirectarylation may be diverted to provide alternative regioisomeric products in high yields. In cases where low reactivity is typically observed, the presence of the carbon−chlorine bond can serve to enhance reactivity and provide superior outcomes. From a strategic perspective, the C−Cl bond is easily
Palladium/2,2′-bipyridyl/Ag2CO3 catalyst for C–H bond arylation of heteroarenes with haloarenes
作者:Shuichi Yanagisawa、Kenichiro Itami
DOI:10.1016/j.tet.2011.03.093
日期:2011.6
Pd/bipy-based catalytic system for the C–Hbondarylation of heteroarenes with haloarenes is described. The complex PdBr2(bipy)·DMSO, whose structure was unambiguously determined by X-ray crystallography, turned out to be a generalcatalyst precursor for the process. The reaction is applicable to a range of electron-rich five-membered heteroarenes, such as thiophenes, thiazoles, benzofurans, and indoles
A palladium NNC-pincer complex efficiently catalyzed the direct arylation of thiophene derivatives with extremely low palladium loadings of the order of parts per million. Thus, the reaction of various thiophenes with aryl bromides in the presence of 25–100 mol ppm of chlorido[(2-phenyl-κ-C 2)-9-phenyl-1,10-phenanthroline-κ2-N,N′]palladium(II) NNC-pincer complex, K2CO3, and pivalic acid in N,N-dimethylacetamide
first example of near-room-temperature α-arylation of benzo[b]thiophenes is reported. The discovery rests on the observation of a switch in α-/β-regioselectivity at different loadings of Pd2(dba)3·CHCl3 in the coupling between benzo[b]thiophene and 4-iodotoluene. We show that this unprecedented regioselectivity switch is driven by a Ag(I)-mediated C–H activation at the α-C–H position, which becomes the
cross-coupling reactions of arylsulfonyl chloride with N-methylpyrrole, furan, thiophene and their derivatives have been achieved in moderate to good yields at room temperature. A plausible mechanism has been proposed for the reaction. The arylation takes place at the C–H bond (C2–H or C5–H) next to the heteroatom with a high regioselective manner! Moreover, arylsulfonyl chlorides utilized in this study are inexpensive