Asymmetric nickel

The asymmetric nickel-catalyzed hydroalumination of prochiral terminal alkenes using adducts of BujAl and chiral amines was reported in 1981 [74], Among the different amines investigated, (-)-N,N-dimethylmenthylamine (DMMA) gave the best enantioselectivities. For example, reaction of 2,3,3-trimethyl-l-butene (39) at room temperature with 0.33 equiv. of the DMMA/iBu3Al adduct in the presence of 0.6 mol% of Ni(mesal)2 gave, after oxidation of the intermediate organoaluminum compounds, 2,3,3-trimethyl-l-butanol 40 in 76% yield and 27% ee (Scheme 2-19). 

A number of chiral monodentate phosphines have been examined in asymmetric nickel-catalyzed reductive couplings of aldehydes and alkynes. The best results to date have been obtained with (+)-NMDPP (16) [33]. Aromatic internal alkynes and branched aldehydes participate with excellent enantiose-lectivity (Scheme 15), although yields and enantioselectivities were somewhat lower with other combinations of aldehydes and alkynes. In a complemen-... 

Asymmetric nickel-catalyzed allylic alkylation with soft carbon-centered nucleophiles was reported in 1996 by Mortreux and his co-workers. Use of a catalytic amount of [Ni(cod)2] together with chiral diphosphines 138 promotes the allylic alkylation of a cyclic ester such as 2-cyclohexenyl acetate with dimethyl malonate in the presence of BSA and gives the corresponding alkylated compounds only with a moderate enantioselectivity (40% ee) (Equation (42)). 

Nickel(0)-catalyzed codimerization of methylenecyclopropanes with electron-deficient olefines are highly regiospedfic, but show a rather poor stereoselectivity. Thus the asymmetric nickel(0)-catalyzed codimerization of methylenecyclopropanes with the chiral bomane derivatives of acrylic acid leads to the optically active 3-methylenecyclopen-... 

In earlier investigations, asymmetric nickel-catalyzed isomerization and cyclodimerization of methylenecyclopropane was found to give l-methylene-2-vinylcyclopentane44. The nickel catalyst system was prepared by reduction of NiBr2L2 with butyllilhium. With tributylphosphane as ligand a 91% yield of the dimerization product was obtained. With dibromobis(( - )-methyl(phenyl)propylphosphane]nickel and butyllithium, optically active (no enantiomeric excesses given) l-methylene-2-vinylcyclopentane of unknown absolute configuration was obtained in 30% yield. Involvement of a n-allyl intermediate is proposed (loc. cit. 141 in ref 45). 

The second protocol for asymmetric nickel-catalyzed reductive coupling utilizes chiral NHC ligands (Scheme 8.29) [52]. The scope was general for alkynes and aldehydes, and enantioselectivities ranged from 65% to 85%. Both internal and terminal aromatic or non-aromatic alkynes were effective participants, as were aromatic and aliphatic aldehydes. 

E. Raluy, M. Dieguez, and O. Pamies, Screening of a modular sugar-based phosphoramidite ligand library in the asymmetric nickel-catalyzed trialkylalu-minum addition to aromatic aldehydes. Tetrahedron Asymmetry, 20 (2009) 1575-1579. 

Baldsing WG, Puffy NW, Newnham RH, Pandolfo AG (2007) High-energy asymmetric nickel-carbon supercapacitors. In Proceedings advanced automotive battery and ultracapacitor conference. Long Beach... 

M. R. Chaulagain, G. J. Sormunene, J. Montgomery, J. Am. Chem. Soc. 2007, 129, 9568-9569. New N-heterocyclic carbene ligand and its application in asymmetric nickel-catalyzed aldehyde/alkyne reductive couplings. 

In 2014, Arai and Yamamoto described asymmetric nickel-catalysed domino Michael/Henry reactions between 2-sulfanylbenzaldehydes and aromatic nitroalkenes to give the corresponding chiral 2-aryl-3-nitrochroman-4-ols, in most cases in almost quantitative yields and with good to high diastereo- and enantioselectivities of up to >98% de and 95% ee, respectively (R = H, Scheme 4.4). These reactions were promoted by an in situ generated catalyst from 10-11 mol% of chiral imidazoline-aminophenol ligand 1 and... 

This ehapter illustrates how much asymmetric nickel catalysis has contributed to the development of novel enantioselective domino, multicomponent, and tandem sequential reactions. It updates the major progress in the field of enantioselective two- and multicomponent domino reactions as well as tandem sequences promoted by chiral nickel catalysts, covering the literature since the beginning of 2004. It well illustrates the power of these... 

In another context, excellent enantioselective nickel-catalysed a-ami-nations of N-Boc-oxindoles with azodicarboxylates have been achieved by using chiral Schiff base nickel catalysts. BINAP ligands have also encountered success in asymmetric nickel-catalysed electrophilic a-aminations and also in combination with other metals such as palladium. On the other hand, the use of other sources of electrophilic nitrogen, such as nitroso compounds and iodinanes, in reactions catalysed by nickel has so far not been described. 

The synthesis of chiral racemic atropisomeric pyridines by cobalt-catalyzed [2 + 2 + 2] cycloaddition between diynes and nitriles was reported in 2006 by Hrdina et al. using standard CpCo catalysts [CpCo(CO)2, CpCo(C2H4)2, CpCo(COD)] [34], On the other hand, chiral complexes of type II were used by Gutnov et al. in 2004 [35] and by Hapke et al. in 2010 [36] for the synthesis of enantiomerically enriched atropisomers of 2-arylpyridines (Scheme 1.18). This topic is described in detail in Chapter 9. It is noteworthy that the 2004 paper contains the first examples of asymmetric cobalt-catalyzed [2 - - 2 - - 2] cycloadditions. At that time, it had been preceded by only three articles dealing with asymmetric nickel-catalyzed transformations [37]. Then enantioselective metal-catalyzed [2 -i- 2 - - 2] cycloadditions gained popularity, mostly with iridium- and rhodium-based catalysts, as shown in Chapter 9. 

Figure 188. Synthesis of asymmetric nickel bis(dithiocarbamate) complexes ftom pVi(S2CNHR)2].

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