Studies on Stereoregulated Reaction Using Organosilicon Reagents and Highly Selective Synteses of Heterocyclic Compounds

近年来，四配位烯丙基硅烷的合成及其在有机合成中的应用受到了广泛的关注。硅-烯丙基sigma键热稳定的烯丙基硅烷可以被高度功能化，所有烯丙基硅烷都被转移到具有高区域选择性、立体选择性和化学选择性的路易斯酸活化的碳亲电试剂上。有机硅化学中最有趣的特征之一是可以分离出稳定的高配位物质。在有机合成中有机硅化合物的扩展中，我们发现了迄今未知的五配位烯丙硅酸酯和相关化合物，可以很容易地制备和用作亲核试剂，其中一些已被报道。主题包括：(1)用烷氧基取代的五配位硅烯丙酸酯的制备，这是一种有用且可储存的试剂，羰基化合物的区域选择性、化学选择性和立体选择性烯丙化反应，以及与光学活性硅烯丙酸酯的不对称烯丙化反应的立体化学结果，这些烯丙化反应由六元环过渡态解释，与四配位硅烯丙酸烯丙化反应的反s_ <E'>机制形成鲜明对比。(2)利用由三烷氧基硅烷和碱金属烷氧化物衍生的烷氧基取代的氢硅酸盐进行羰基化合物的化学和立体选择性还原，以及利用氢硅酸盐催化前手性酮的新的不对称还原。(3)钯配合物在立体选择模式下催化烯烃硅酸酯与有机卤化物和三氟酸酯的交叉偶联反应。(4)合成了难以获得且不可分离的高活性物质，制备了有机硅试剂，作为烷基二氮亚甲基衍生物的合成等价物，并与烯烃、羰基和羰基化合物反应，产率高，得到相应的[3+2]环加合物。

Much attention has been recently focused on both syntheses of tetracoordinate allylsilanes and their applications to organic synthesis. Allylsilanes whose silicon-allyl sigma-bond is thermally stable can be highly functionalized allvl are transferred onto carbon electrophiles activated by a Lewis acid with high regio-, stereo- and chemoselectivity. One of the most interesting features in organosilicon chemistry is that stable high coordinate species can be isolated. In an extension of organosilicon compounds in organic synthesis, we have found that pentacoordinate allylsiliconates and related compounds, unknown hitherto, can be readily prepared and used as nucleophiles, some of which are reported.Topics are (1) preparations of pentacoordinate allylsiliconates, substituted by alkoxy groups, which are useful and storable reagents, regio-, chemo- and stereoselective allylations of carbonyl compounds without catalyst, and stereochemical outcomes of asymmetric allylation with optically active allylsiliconates which are interpreted by a six-membered cyclic transition state, in sharp contrast with an anti-S_<E'> mechanism for the allylation using tetracoordiante allylsilane, (2) Chemo- and stereoselective reductions of carbonyl compounds using alkoxy-substituted hydridosiliconates derived from trialkoxysilane and alkali metal alkoxides, and new catalytic asymmetric reductions of prochiral ketone using hydridosiliconates. (3) Cross-coupling reactions of alkenylsiliconates with organic halides and triflates catalyzed by a palladium complex in a stereoselective mode. (4) Syntheses of highly reactive species which were hardly obtainable and not isolable were achieved, Organosilicon reagents that acted as a synthetic equivalent of alkylideneazomethine ylids were prepared and allowed to react with alkenes, carbonyl and thicarbonyl compounds to give the corresponding [3+2] cycloadducts in high yields.