Nickel complex, cross-coupling reaction

One of the challenges is to extend the reaction from triflates to less reactive arylsulfonates. The palladium-catalyzed reaction of aryl mesylates results in low yields because of their slow oxidative addition to a palladium(O) complex, but they readily participate in the nickel-catalyzed cross-coupling reaction at 80°-100 °C. A nickel(O) species incorporating dppf ligand, obtained by in situ reduction of 10 mol% of NiCljCdppf) with zinc dust, is recognized as the most effective catalyst (Eq. 43). However, again the reaction needs to be optimized because a... 

Alkyl- and aryl-pyridazines can be prepared by cross-coupling reactions between chloropyridazines and Grignard reagents in the presence of nickel-phosphine complexes as catalysts. Dichloro[l,2-bis(diphenylphosphino)propane]nickel is used for alkylation and dichloro[l,2-bis(diphenylphosphino)ethane]nickel for arylation (78CPB2550). 3-Alkynyl-pyridazines and their A-oxides are prepared from 3-chloropyridazines and their A-oxides and alkynes using a Pd(PPh3)Cl2-Cu complex and triethylamine (78H(9)1397). 

Carbon-carbon bond-forming reactions are one of the most basic, but important, transformations in organic chemistry. In addition to conventional organic reactions, the use of transition metal-catalyzed reactions to construct new carbon-carbon bonds has also been a topic of great interest. Such transformations to create chiral molecules enantioselectively is therefore very valuable. While various carbon-carbon bond-forming asymmetric catalyses have been described in the literature, this chapter focuses mainly on the asymmetric 1,4-addition reactions under copper or rhodium catalysis and on the asymmetric cross-coupling reactions catalyzed by nickel or palladium complexes. 

Nickel complexes seem to be especially suited to catalyze cross-coupling reactions, in which both partners are sp3-hybridized. Scott and coworkers noted... 

B. Cross-coupling Reactions of Grignard Reagents in the Presence of Nickel Complexes... 

Nickel/carbene complexes have also been successfully employed in the Suzuki-Miyaura cross-coupling reaction. One of the first successful applications of this was demonstrated by Blakey and MacMillan, wherein boronic acids were coupled with aryltrimethylammonium salts [52]. It was found that the transformation could be accomplished using 10 mol % Ni(COD)2,... 

The nickel(ll) carbene complexes were used in the Suzuki-Miyaura cross-coupling reaction between phenylboronic acid and p-chloroacetophenone. The yield was low (10-15% depending on the carbene s auxiliary wingtip group), but could be improved to quantitative (92-95% isolated) upon addition of 2 equiv. of PPhj. 

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