Homobimetallic Transition Metal Schiff Base Catalysts

3 Homobimetallic Transition Metal Schiff Base Catalysts 

As shown in Fig. 8, the Ni2-lb complex was applicable to broad range of catalytic asymmetric reactions under simple proton transfer conditions [19-30]. As donors in direct Mannich-type reactions, not only a-nitroacetates, but also malonates, p-keto esters [22], p-keto phosphonates [23], and a-ketoaniUdes [24] gave excellent enantioselectivity and diastereoselectivity. It is noteworthy that the Ni2-lb complex also promoted vinylogous direct catalytic asymmetric Mannich-type reaction of an a,p-unsaturated y-butyrolactam, giving synthetically versatile functionalized a,p-unsaturated y-butyrolactam in 99% ee [25]. Because the Ni2-lb 

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