Transition Metal-Catalyzed Addition Reaction to Alkynylmetals with Migration of Metal Moieties

在催化量的PBu_3配位的钌配合物存在下，炔基锡烷（R^1C = CSnBu_3）与端炔（R^2C=CH）发生加成反应，锡基发生1，2-位移，生成（E）-和（Z）-1-三丁基锡基丁-1-烯-3-炔（Bu_3SnC（R^1）=CHC=CR^2）.加成反应适用于具有芳香族和/或脂肪族取代基的底物的各种组合，立体化学结果很大程度上取决于这些取代基的特征。脂肪族末端炔的反应以完美的立体选择性进行，其中炔基锡烷上的取代基R^1决定了构型：R^1的E =烷基，R^1的Z =芳基。与此相反，芳基乙炔的反应得到了立体异构体的混合物，而与炔基锡烷上取代基R^1的性质无关。由钌配合物和炔基锡烷通过锡烷基的迁移生成的钌-β-锡烷基亚乙烯基配合物可能作为关键中间体参与反应，其接受末端炔的C-H键加成以得到相应的锡烯炔。密度泛函理论计算表明，钌-β-锡烷基亚乙烯基配合物形成过程中锡基的1，2-位移比端炔的1，2-氢位移更容易发生.在此基础上讨论了取代基对立体选择性的影响。

In the presence of a catalytic amount of a ruthenium complex coordinated with PBu_3, alkynylstannanes (R^1C≡CSnBu_3) were found to accept the addition of terminal alkynes (R^2C=CH) with 1, 2-shift of the stannyl group to give (E)-and (Z)-1-tributylstannylbut-1-en-3-ynes (Bu_3SnC(R^1)=CHC=CR^2). The addition reaction is applicable to various combination of substrates having an aromatic and/or aliphatic substituent, the stereochemical outcome depending largely on the character of these substituents. The reaction of aliphatic terminal alkynes proceeds in perfect stereoselectivities, where substituent R^1 on alkynylstannanes determines the configuration : E for R^1 = alkyl and Z for R^1 = aryl. In contrast, the reaction of arylacetylenes gave a mixture of stereoisomers irrespective of the character of substituent R^1 on the alkynylstannane. Ruthenium-β-stannylvinylidene complexes generated from a ruthenium complex and an alkynylstannane with migration of the stannyl group is likely to be involved in the reaction as key intermediates, which accept addition of a C-H bond of terminal alkynes to give the corresponding stannylenynes. DFT calculation clearly shows that the 1, 2-shift of the stannyl group on formation of ruthenium-β-stannylvinylidene complexes is more facile than the corresponding 1, 2-hydrogen shift of the coordinating terminal alkynes. The effect of substituents on the stereoselectivity also is discussed based on the calculation.