STUDIES ON NOVEL ORGANIC REACTION AND STEREO-REGULATION USING SILICON-, TIN-, AND RELATED ELEMENT COMPOUNDS

1. 五配位有机硅的高选择性烯丙基化在有机硅化学中最有趣的特点之一是可以分离出稳定的高配位物质。我们发现，迄今未知的五配位烯丙硅酸盐及其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：制备有用且可储存的烷氧基取代的五配位硅酸烯丙基，羰基化合物无催化剂的区域化学和立体选择性烯丙基化，以及光学活性硅酸烯丙基不对称烯丙基化的立体化学结果，这些烯丙基化由六元环过渡态解释，与四配位硅酸烯丙基化的反se ^1机制形成鲜明对比新合成的烷基二氮亚甲基和相关的1,3-偶极试剂及其在有机合成中的应用^2氮亚甲基和相关的1,3-偶极试剂无论从合成角度还是从理论角度来看都是重要而有趣的化学种类。如果偶极中心没有被吸电子或共轭基团稳定，这些物质通常是不稳定的和不可接近的。我们在这里报道了多种N-硅基甲基取代的烯酮N， s -缩醛在氟化铯的存在下与活化的烯烃、羰基化合物和硫酮顺利反应，通过甲基硫代三甲基硅烷的1,3消去生成α -烷基二吡啶、恶唑烷和噻唑烷。同样，n -硅基甲基取代异硫脲与氟离子促进的羰基和硫羰基化合物反应，得到相应的[3 + 2]环加合物、2-亚胺-1,3-恶唑烷和2-亚胺-1,3-噻唑烷，收率很高。这些试剂可以看作是烷基烷酰亚甲酰亚胺和亚氨基亚甲酰亚胺的合成等价物。

1. Highly Selective Allylation Using Pentacoordinate Organosilicates On of the most interesting features in organosilicon chemistry is that stable high coordinate species can be isolated. We have found that pentacoordinate allylsilicates and related compounds, unknown hitherto, can be readily prepared and used as nucleophiles, some of which are reported. Topics are preparation of pentacoordinate allylsilicates, 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 allylsilicates which are interpreted by a six-membered cyclic transition state, in sharp contrast with an anti-SE^1 mechanism for the allylation using tetracoordinate allylsilane.2 Novel Synthesis of Alkylideneazomethine Yilds and Related 1,3-Dipolar Reagents and Synthetic Application to Organic Synthesis^2 Azomethine ylids and related 1,3-dipolar reagents are important and interesting chemical species from both synthetic and theoretical points of view. These species are generally unstable and inaccessible if the dipolar centers are not stabilized by electron-withdrawing or conjugating groups. We report here that a variety of N-silylmethyl-substituted ketene N,S-acetals react smoothly with activated alkenes, carbonyl compounds, and thioketones in the presence of cesium fluoride, to afford alpha-alkylidenepyrrolidines, oxazolidines, and thiazolidines, via a 1,3-elimination of methylthiotrimethylsilane. Similarly, N-silylmethyl- substituted isothioureas react with carbonyl and thiocarbonyl compounds promoted by fluoride ion to give the corresponding [3 + 2] cycloadduct, 2-imino-1,3-oxazolidines and 2-imino-1,3-thiazolidines in good yield. These reagents can be viewed as synthetic equivalents of alkylideneazomethine ylids and iminoazomethine ylids.