Several unsymmetrical heterobiaryls have been synthesized through palladium-catalyzed cross-coupling reactions of lithium triorganozincates. The latter have been prepared by deprotonative lithiation followed by transmetalation using non hygroscopic ZnCl2*TMEDA (1/3 equiv).
Palladium-Catalyzed Cross-Couplings of Lithium Arylzincates with Aromatic Halides: Synthesis of Analogues of Isomeridianin G and Evaluation as GSK-3β Inhibitors
Several analogues of isomeridianin G have been synthesized using palladium-catalyzedcross-couplingreactions of lithium triorganozincates as a key step. The latter have been prepared by deprotonative lithiation followed by transmetalation using ZnCl2˙TMEDA (0.33 equiv). cross-coupling - heterocycles - palladium - zinc - lithium
Pd-catalyzed oxidative C–H/C–H cross-coupling of pyridines with heteroarenes
作者:Bo Liu、Yumin Huang、Jingbo Lan、Feijie Song、Jingsong You
DOI:10.1039/c3sc50348h
日期:——
We have developed for the first time a general, concise and highly selective method for the C2-heteroarylation of pyridines and related azines with a broad range of heteroarenes via a two-fold C–H activation, which streamlines the previous approaches that require the activated azine N-oxide as the coupling partner.
Thiophene was regioselectively deprotonated at C2 on treatment with 1/3 equiv of Bu3MgLi in THF at room temperature. The lithium arylmagnesate formed was either trapped with electrophiles or cross-coupled in a 'one-pot' procedure with aryl halides under palladium catalysis. 2-Chlorothiophene and 2-methoxythiophene were similarly deprotonated at C5 under the same reaction conditions. The enhancement of the reactivity of the base using TMEDA was evidenced using H-1 NMR spectroscopy. (c) 2005 Elsevier Ltd. All rights reserved.