Nickel-Catalyzed Sp~2C-P Bond Formation Via [P]-H/C-CN Cross Couplings

Arylphosphorus compounds have wide applications in agrochemistry, medicinal chemistry, material chemistry, organic synthesis and catalysis. The preparation of arylphosphorus compounds depends on the transformation of toxic and difficulty preparative organohalides. Thus, development of more efficient and simpler transformations, replacing the traditional toxic organohalides centered synthetic systems of organophosphorus compounds, still is highly desired. Aryl nitriles are readily available chemicals which are widely used for constructing carbon-carbon bonds. However, noble metal catalysts and/or phosphine ligands are usually required in those transformations. Herein, we report an efficient synthesis of both arylphosphines and arylphosphine oxides from the readily available P-H compounds and aryl nitriles by using the [P]-H/C-CN direct cross coupling strategy. This transformation proceeds smoothly with a simple Ni(COD)2/8-hydroxyquinoline catalyst, providing an alternative protocol for the construction of sp2C-P bonds under mild reaction conditions. The results were summarized as follows:1. Ni(COD)2/8-hydroquinoline catalyzed synthesis of arylphosphine oxides via P(O)-H/C-CN cross coupling.Catalyzed by Ni(COD)2/8-hydroquinoline, in the presence of t-BuOK, the cross coupling of aromatic nitriles with secondary phosphine oxides proceed smoothly at 90 ?, producing the corresponding arylphosphine oxides. Electron-donating group substituted aromatic nitriles could couple with diphenylphosphine oxide efficiently, whereas the electron-withdrawing group substituted aromatic nitriles show low reaction efficiency and only trace amount of products are generated. The ortho-substituted aromatic nitriles also showed low efficiency, probably due to the high steric hindrance. Under the reaction conditions, other secondary phosphine oxides also serve as the good substrates, give the expected arylphosphine oxides.2. Ni(COD)2/8-hydroquinoline catalyzed synthesis of arylphosphines via P-H/C-CN cross coupling.Under the reaction conditions, besides the secondary phosphine oxides, the highly coordinative secondary phosphines also couple with aromatic nitriles. Catalyzed by 10 mol% Ni(COD)2/8-hydroquinoline, in the presence of t-BuOK, diphenylphosphine directly couples readily with a variety of aromatic nitriles, producing the corresponding valuable phosphine ligands.