Study of Cationic Palladium Complex-Catalyzed Cyclization-Hydrosilylation of α,ω-Diynes

1)利用钯催化的L-炔烃与三氯硅烷的二聚-氢硅丙酮反应，我们合成了一种阳离子钯配合物，它对分子内二聚-氢硅化反应，即α，ω-烷基二炔的环化-氢硅烷化反应表现出特殊的催化活性。因此，我们以典型的三氯硅烷为原料，从1，6-庚二炔及其同系物出发，合成了5，6-元(甚至7元)(Z)-1-(trichlosilyl)methylene-2-mthylenecycloalkanes。为了阐明这一独特反应的可能的催化循环，我们进行了不对称的1，6-辛二炔的环化-硅氢化反应，得到了专有的，(Z)-1(1‘-三氯苯基)乙叉-2-亚甲基环戊烷。结果很好地表明，加氢缩合发生在末端的炔位，得到亚乙叉-钯物种，后者又经历了与环状…的内部炔位的碳氢缩合。更多的ZE，然后用氢硅烷取代，形成观察到的产物，并很可能再生氢化钯作为活性催化剂。值得注意的是，HSiMe_nCl_(3n)(n=0-2)同样适用于这种催化环化-氢硅化反应，而不适用于上述1-炔烃的二聚-氢硅化反应。2)以9-氧杂-1-十二烯-6，11-二炔为底物，以三氯硅烷为添加剂的阳离子钯配合物催化的环化-氢硅化反应得到了意想不到的反应产物。鉴定出的主要产物(75%)是由内部炔位和末端烯烃之间的环合反应产生的，而次要产物(25%)是由普通的分子内二炔环合反应得到的。此外，我们还发现α，ω-烯烃发生环化-硅氢化反应的速度一般比相应的α，ω-烷基二炔快得多。这一结果可能表明，在上述催化循环中，烯位的碳氢加成反应必须明显地比在炔位的碳钯反应增强。因此，在逻辑上建议进行任何硅氢化交叉偶联的烯烃和烯烃。较少

1)Taking advantage of the findings involving the palladium-catalyzed dimerization-hydrosilylalon of l-alkynes with trichlorosilane, we have developed a cationic palladium complex, which exhibits a specific catalytic activity for an intramolecular dimerization-hydrosilylation, i.e., cyclization-hydrosilylation of α,ω-alkadiynes. Thus, we have prepared 5, 6-membered (or even 7-membered) (Z)-1-(trichlosilyl)methylene-2-mthylenecycloalkanes starting from 1,6-heptadiyne derivatives and their homologs using typically trichlorosilane as an added.In order to elucidate a possible catalytic cycle of this unique reaction, the cyclization-hydrosilylation of unsymmetrical 1,6-octadiyne was carried out to give exclusively, (Z)-1(1'-trichlorosityl)ethylidene -2-methylenecyclopentane. The results well implicate that the hydropalladation takes place at a terminal alkyne site giving a vinylidene-palladium species, the latter, in turn, undergoing the carbopalladation with an internal alkyne site to cycli … More ze, followed by substitution with the hydrosilane to form the observed product and regenerate most probably a hydridopalladium as an acive catalyst. It is worthy of note that HSiMe_nCl_(3n) (n = 0 - 2) are equally applicable to this catalytic cylization-hydroilylation, while this is not the case for the dimerization-hydrosilylation of 1-alkynes mentioned above.2)Truly unexpected reaction product has been obtained when 9-oxa-1-dodecen-6,11-diyne was used as a substrate in the cationic palladium complex-catalyzed cyclization-hydrosilylation using trichlorosilane as an added. The major product (75%) identified was the one arising from the cyclization between an internal alkyne site and a terminal alkene, whereas the minor product (25%) was obtained from the ordinary intramolecular diyne cyclization. Furthermore, we have experienced that α,ω-alkenynes undergo the present cyclization-hydrosilylation generally much faster than the corresponding α,ω-alkadiynes.The results may suggest that, in the above mentioned catalytic cycle, the tale of carbopalladation at the alkene site must clearly be enhanced than that at the alkyne site. Thus, it is logically suggested to conduct any hydrosilylative cross-coupling of alkynes with alkenes. Less