Synthesis of symmetrical bisquinolones via nickel(0)-catalyzed homocoupling of 4-chloroquinolones
A method for the gram-scale preparation of functionalized 4,4′-bisquinolones using a microwave-assisted Ullmann-type homocoupling reaction is described. The method is catalytic in nickel(O) which is generated in situ by reduction from an inexpensive nickel(II) source and utilizes readily available 4-chloroquinolin-2(1H)-ones as starting materials. In contrast to the alternative palladium(0)-catalyzed one-pot borylation/Suzuki crosscoupling reaction, the new method avoids the use of an expensive catalyst and cross-coupling partner such as bis(pinacolato)diboron.
Nickel-catalyzed cross-coupling reactions of 4-mesylcoumarins with aryl halides: Facile synthesis of 4-substituted coumarins
A new and efficient nickel-catalyzed cross-coupling reaction between 4-mesylcoumarins and aryl halides was developed to give a number of 4-arylcoumarins in good yield under mild conditions. Unlike the previously reported coupling examples, this new method allows the direct cross-coupling of 4-mesylcoumarins with aryl- or vinyl halides in the NiCl2(PPh 3)2/PPh3/Zn/toluene system. This has greatly facilitated the synthesis of biologically useful 4-substituted coumarins.
Lei, Jian-Guang,Xu, Ming-Hua,Lin, Guo-Qiang
p. 2364 - 2368
(2007/10/03)
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