Cobalt-Catalyzed CH Bond Functionalizations with Aryl and Alkyl Chlorides
作者:Benudhar Punji、Weifeng Song、Grigory A. Shevchenko、Lutz Ackermann
DOI:10.1002/chem.201301409
日期:2013.8.5
catalytic CH bond arylations on heteroaryl‐substituted arenes with widely available aryl chlorides, which set the stage for the preparation of sterically hindered tri‐ortho‐substituted biaryls. Likewise, challenging direct alkylations with β‐hydrogen‐containing primary and even secondary alkyl chlorides proceeded on pyridyl‐ and pyrimidyl‐substituted arenes and heteroarenes. The cobalt‐catalyzed CH bond
achieved by Ru(II)−carboxylate‐catalyzed reaction with aryl bromides in water, whereas meta‐substituted phenylpyrimidines selectively led to monoarylation. The reaction is strongly accelerated under microwave irradiation, and is compatible with various functional groups on both coupling partners. As established from Hammett plots, electron‐withdrawinggroups on the pyrimidine substrates facilitate the
Two protocols for the nickel-catalyzed cross-coupling of aryl fluorides with aryl boronic esters have been developed. The first employs metal fluoride cocatalysts, such as ZrF4 and TiF4, which enable Suzuki-Miyaura reactions of aryl fluorides bearing electron-withdrawing (ketones, esters, and CF3), aryl and alkenyl groups as well as those comprising fused aromatic rings, such as fluoronaphthalenes and fluoroquinolines. The second protocol employs aryl fluorides bearing ortho-directing groups, which facilitate the difficult C-F bond activation process via cyclometalation. N-heterocycles, such as pyridines, quinolines, pyrazoles, and oxazolines, can successfully promote cross-coupling with an array of organoboronic esters. A study into the substituent effects with respect to both coupling components has provided fundamental insights into the mechanism of the nickel-catalyzed cross-coupling of aryl fluorides.