Conjugate addition nickel-catalysed

Alkynes in combination with a catalytic amount of a nickel complex have been found to catalyse the conjugate addition of arylboron reagents to ,/3-unsaturated carbonyl compounds.238... 

Nickel or palladium catalysed conjugate addition and other carbozincation reactions... 

Nickel catalysed conjugate addition of b/s(p-tolyl)zinc to 3-methyl-2-cyclopent-1-one to give S-methyl-S-lp-tolyllcyclopentanone58... 

Kanemasa, S., Oderatoshi, Y. and Wada, E. (1999) Asymmetric conjugate addition ofthiols to a 3-(2-alkenoyl)-2-oxazolidinone catalysed by the DBFOX/Ph aqua complex of nickel(II) perchlorate. Journal of the American Chemical Society, 121, 8675-8676. 

A closely related asymmetric reaction is the nickel catalysed conjugate addition of dialkylzincs to Michael acceptors such as chalcone. Here, ACTC 63 showed the best performance [45]. A catalyst loading of 5 mol% of nickel salt was sufficient, albeit a high ligand loading of 50 mol% was necessary in order to suppress catalysis by achiral species, and the product was obtained in 90% chemical yield and with an enantiomeric excess of 62%, Scheme 12. 

A nickel-catalysed reductive conjugate addition to enones was recently reported. This method leads to coupling of an a,p-unsaturated ketone or aldehyde with an organic halide in the presence of triallg lchlorosilane and a... 

The use of pyridine (31) as additive allowed for more selective and efficient nickel-catalysed arylations of styrenes (Scheme 10.10) [32, 33]. Aryl and alkyl bromides gave good yields of isolated products. With respect to the latter, secondary alkyl bromides proved superior to primary ones. However, use of methyl acrylate (1) as substrate yielded predominantly products originating from conjugate additions, rather than Mizoroki-Heck-type reactions. 

Enantioselective Nickel(ii)-Catalysed Conjugate Addition Reactions... 

Scheme 2.1 First enantioselective nickel-catalysed conjugate additions reported by Soai et aL in 1988-1989.

Among the most successful catal)rtic systems employed in enantioselective nickel-catalysed Michael additions of nucleophiles to nitroalkenes is that developed by Evans and Seidel in 2005, which allowed enantioselectivities of up to 95% ee to be achieved in the enantioselective conjugate additions of 1,3-dicarbonyl compounds to nitroalkenes (Scheme 2.3). Products resulting... 

In 2012, Wu et al reported a practical large-scale preparation of the antidepressant drug (i )-rolipram from isovanilline, the key step of which was an enantioselective nickel-catalysed conjugate addition of diethyl malonate to a functionalised nitroalkene. Using only 1 mol% of catalyst the reac-... 

Chiral p-alkynyl acids constitute an important class of pharmaceutical compounds with diverse biological activities however, their asymmetric synthesis remains a significant challenge. In this context, Peng and Shao have reported the first metal-catalysed asymmetric conjugate addition of malonates to nitroenynes promoted by a simple chiral nickel catalyst, which allowed a novel route to this type of chiral product. As shown in Scheme 2.11 the 1,4-conjugate addition of malonates to nitroenynes catalysed by 2 mol% of preformed diamine nickel catalyst afforded the corre-... 

Very recently, the same authors reported the first catalytic asymmetric approach to octahydroindolones, which was based on the enantioselective nickel-catalysed conjugate addition of tert-butyl malonate to a nitrodi-enyne. In the presence of a chiral catalyst generated in situ from NiBr2 and chiral diamine 7, the 1,4-conjugate addition proceeded smoothly to provide the corresponding enantioenriched 1,3-enyne in 91% yield and with 93% ee, as shown in Scheme 2.12. It was worth noting that 1,6- or 1,8-addition was not observed. The formed functionalised product could be further decarbox-ylated and then cyclised into the corresponding cyclohexanone, which was... 

In 2014, Hamashima and Kan reported the practical total syntheses of acro-melic acids A and B, having potent neuro-excitatory activity, which were based on enantioselective nickel-catalysed asymmetric conjugate additions of a-keto esters to nitroalkenes. Indeed, the key steps of the syntheses of these natural... 

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