Conjugate additions of [Zn(bpy*)Cl(Et)] (bpy* = 4,4'-di-tert-butyl-2,2'-bipyridine) to cyclohex-2-en-1-one are promoted by ZnMe2 in 88% ee but in moderate yield under CuI phosphoramidite catalysis. In the absence of ZnMe2 the [Zn(bpy*)Cl(Et)] is inactive indicating a Schlenk-type equilibrium. Other derivatives of [Zn(bpy*)Cl(R)] (R = Bu, 4-methylbenzyl), prepared in situ from [ZnCl(R)] and the bipyridine give low yields due to competing chloride abstraction. 13C NMR studies indicate facile organo-ligand exchange between [Zn(bpy*)(Et)2] and [Zn(bpy*)Cl2] complexes. In the presence of the bipyridine, [ZnBr(allyl)] disproportionates into [Zn(bpy*)Br2] and [Zn(bpy*)(allyl)2] species. In separate studies, simple (E)-MeCH=CHCONMeR (R = Me, OMe) α,β-unsaturated amides undergo asymmetric 1,4-addition of EtMgBr in 75-99% yield and 48-79% ee in the presence of the diphosphines JosiPhos or MeDuPhos and copper(I) sources.
[Zn(bpy*)Cl(Et)](bpy* = 4,4'-二-tert-丁基-
2,2'-联吡啶)对环己-2-烯-1-酮的共轭加成在ZnMe2的催化下可以得到88%的对映选择性,但产率中等,在CuI
磷酰胺催化下则较低。在没有ZnMe2的情况下,[Zn(bpy*)Cl(Et)]是不活性的,表明存在Schlenk型平衡。[Zn(bpy*)Cl(R)]的其他衍
生物(R = Bu,4-甲基苄基),从[ZnCl(R)]和联
吡啶中原位制备,由于竞争性
氯离子引发的脱除反应导致产率较低。13C NMR研究表明,[Zn(bpy*)(Et)2]和[Zn(bpy*)Cl2]配合物之间易于发生有机
配体交换。在联
吡啶的存在下,[ZnBr(烯丙基)]会不均分为[Zn(bpy*)Br2]和[Zn(bpy*)(烯丙基)2]物种。在单独的研究中,简单的(E)-MeCH = CHCONMeR(R = Me,OMe)α,β-不饱和酰胺在
双膦JosiPhos或MeDuPhos和
铜(I)源的存在下,可以以75-99%的产率和48-79%的对映选择性进行不对称1,4-加成反应。