Enantioselective α-arylation of ketones with aryl triflates catalyzed by difluorphos complexes of palladium and nickel
Enantioselective α-arylation of ketones with aryl triflates catalyzed by difluorphos complexes of palladium and nickel
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DOI：
10.1021/ja074453g
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发表时间：
2008-01-09
影响因子：
15
通讯作者：
Hartwig, John F.
中科院分区：
文献类型：
--
作者：
Liao, Xuebin;Weng, Zhiqiang;Hartwig, John F.
描述了酮与芳基三氟甲磺酸酯的不对称α-芳基化，并且使用这种亲电试剂与含有segphos衍生物的镍和钯催化剂，实质上增加了酮烯醇化物的高度对映选择性芳基化的范围。以三氟甲磺酸芳基酯为反应物，三氟磷为配体，钯催化剂用于中性或富电子的三氟甲磺酸芳基酯的反应，镍催化剂用于贫电子的三氟甲磺酸芳基酯的反应，合成了四氢萘酮、茚满酮、环戊酮和环己酮衍生物的一系列α-芳基化反应。对映体选择性为70%~ 98%，其中10个实例超过90%。对这些α-芳基化反应的系统研究揭示了许多影响对映选择性的因素。含有具有较小二面角的联芳基骨架的配体产生比具有较大二面角的相关配体具有更高对映选择性的催化剂。此外，三氟甲磺酸芳基酯的反应速率相对于芳基溴化物的反应速率更快，使得三氟甲磺酸芳基酯的α-芳基化可以在较低温度下进行，并且该较低温度改善了对映选择性。最后，将催化反应的对映选择性与分离的[（segphos）Pd（Ar）（Br）]、[（segphos）Pd（Ar）（I）]和[（segphos）Ni（C6 H4 -4CN）Br]的化学计量反应的对映选择性进行比较的研究表明，催化剂分解影响对映选择性。
The asymmetric alpha-arylation of ketones with aryl triflates is described, and the use of this electrophile with nickel and palladium catalysts containing a segphos derivative increases substantially the scope of highly enantioselective arylations of ketone enolates. The combination of aryl triflates as reactant, clifluorphos as ligand, palladium catalysts for reactions of electron-neutral or electron-rich aryl triflates, and nickel catalysts for reactions of electron-poor aryl triflates led to a series of alpha-arylations of tetralone, indanone, cyclopentanone, and cyclohexanone derivatives. Enantioselectivities ranged from 70% to 98% with 10 examples over 90%. Systematic studies on these alpha-arylations have revealed a number of factors that affect enantioselectivity. Ligands containing biaryl backbones with smaller dihedral angles generate catalysts that react with higher enantioselectivity than related ligands with larger dihedral angles. In addition, faster rates for reactions of aryl triflates versus those for reactions of aryl bromides allow the a-arylations of aryl triflates to be conducted at lower temperatures, and this lower temperature improves enantioselectivity. Finally, studies that compare the enantioselectivities of catalytic reactions to those of stoichiometric reactions of isolated [(segphos)Pd(Ar)(Br)], [(segphos)Pd(Ar)(l)], and [(segphos)Ni(C6H4-4CN)Br] suggest that catalyst decomposition affects enantioselectivity.