Asymmetric conjugate addition chiral nickel complex

The asymmetric conjugate addition of diethylzinc with chalcone was also catalyzed by nickel and cobalt complex (Eq. (12.31)) [71]. A catalytic process was achieved by using a combination of 17 mol% of an aminoalcohol 34 and nickel acetylacetonate in the reaction of diethylzinc and chalcone to provide the product in 90% ee [72, 73]. Proline-derived chiral diamine 35 was also effective, giving 82% ee [74]. Camphor-derived tridentate aminoalcohol 36 also catalyzes the conjugate addition reaction of diethylzinc in the presence of nickel acetylacetonate to afford the product in 83% ee [75]. Similarly, the ligand 37-cobalt acetylacetonate complex catalyzes the reaction to afford the product in 83% ee [76]. 

Various other examples of nickel-catalyzed asymmetric addition of organozinc compounds to enones have been reported using different chiral auxiliaries111-117. Complexes of other transition metals, such as rhodium118-119, lanthanum120, and titanium121, have also been found to promote asymmetric conjugate addition of enolates to a,/i-unsaturated ketones. 

Nickel complexes, prepared by the combination of Ni(acac)2 with a chiral P-ami-no alcohol [24,25] or a P-hydroxysulfoximine [26], catalyze the conjugate addition of diethylzinc to chalcone. Some asymmetric ampHfications have been observed. 

---