Switch of Regioselectivity in Palladium-Catalyzed Silaboration of Terminal Alkynes by Ligand-Dependent Control of Reductive Elimination
Switch of Regioselectivity in Palladium-Catalyzed Silaboration of Terminal Alkynes by Ligand-Dependent Control of Reductive Elimination
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DOI：
10.1021/ja105096r
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发表时间：
2010-09-08
影响因子：
15
通讯作者：
Suginome, Michinori
中科院分区：
文献类型：
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作者：
Ohmura, Toshimichi;Oshima, Kazuyuki;Suginome, Michinori
甲硅烷基硼酸酯加成到末端炔烃的区域选择性可以通过钯催化剂上磷配体的选择来切换。在(eta(3)-C(3)H(5))Pd(PPh(3))Cl (1.0 mol%)存在下，硅化反应以正常的区域选择性进行，以高产率得到1-硼基-2-甲硅烷基-1-烯烃。与此形成鲜明对比的是，当使用带有 P(t-Bu)(2)(联苯-2-基) 的钯催化剂进行反应时，会选择性地形成反相异构体 2-硼基-1-甲硅烷基-1-烯烃。提出了一种涉及可逆插入/β-硼基消除步骤的区域选择性变化的反应机制。
The regioselectivity in the addition of silylboronic esters to terminal alkynes can be switched by the choice of phosphorus ligands on the palladium catalysts. The silaboration proceeds with normal regisoselectivity in the presence of (eta(3)-C(3)H(5))Pd(PPh(3))Cl (1.0 mol %) to give 1-boryl-2-silyl-1-alkenes in high yields. In sharp contrast, selective formation of the inverse regioisomers, 2-boryl-1-silyl-1-alkenes, takes place when the reaction is carried out with a palladium catalyst bearing P(t-Bu)(2)(biphenyl-2-yl). A reaction mechanism for the change of regioselectivity that involves reversible insertion/beta-boryl elimination steps is proposed.