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An Electron‐Deficient Diene as Ligand for Palladium‐Catalyzed Cross‐Coupling Reactions: An Efficient Alkylation of Aryl Iodides by Primary and Secondary Alkylzinc Reagents
Authors:Qiang Liu  Hui Duan  Xiancai Luo  Yang Tang  Gang Li  Rong Huang  Aiwen Lei
Abstract:An electron‐deficient diene, L1 , was found to be an effective ligand in facilitating palladium‐catalyzed Negishi couplings involving primary and secondary alkylzinc reagents. The reactions took place readily at 60 °C in THF with 5 mol% of a catalyst generated in situ from bis(acetonitrile)palladium dichloride [PdCl2(MeCN)2] and L1 , and functional groups such as chloro, bromo, etc. attached to phenyl ring as well as β‐H atoms adjacent to the reaction site were well tolerated. The problematic isomerizations in secondary alkyzinc reagents involved in the reactions reported in the literature were also observed in our system when isopropylzinc chloride was employed alone as the nucleophile. However, the isomerization was significantly suppressed when i‐Pr2Zn was utilized in the presence of L1 .
Keywords:alkylation  alkylzinc reagents  C?C coupling  diene ligand  palladium
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